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Cited by 103Non-Invasive Vital Sign MonitoringOptical Imaging and Spectroscopy TechniquesAnalytical Chemistry and Sensors

The Current State of Optical Sensors in Medical Wearables

Open access
Vavrinsky, Erik, Esfahani, Niloofar Ebrahimzadeh, Hausner, Michal, Kuzma, Anton, Rezo, Vratislav, Donoval, Martin, Kosnacova, Helena·2022·Biosensors
DOI 10.3390/bios12040217PMC PMC9029995
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Abstract

Optical sensors play an increasingly important role in the development of medical diagnostic devices. They can be very widely used to measure the physiology of the human body. Optical methods include PPG, radiation, biochemical, and optical fiber sensors. Optical sensors offer excellent metrological properties, immunity to electromagnetic interference, electrical safety, simple miniaturization, the ability to capture volumes of nanometers, and non-invasive examination. In addition, they are cheap and resistant to water and corrosion. The use of optical sensors can bring better methods of continuous diagnostics in the comfort of the home and the development of telemedicine in the 21st century. This article offers a large overview of optical wearable methods and their modern use with an insight into the future years of technology in this field.

Verified 2026-10-09 · 2 references not checked yet

AI snapshot

Written from the paper’s full text.

TL;DR

This review surveys optical sensors for medical wearables across photoplethysmography, radiation, optical fiber, and biochemical sensing. It argues these sensors offer non-invasive, miniaturizable, electromagnetically immune monitoring, while noting persistent challenges in ambient light, penetration depth, stability, and biocompatibility.

Key findings

  • Optical sensors are already significant in wearables: about 15% of the wearable-device market is based on optical sensors, and the wearable medical market is projected to grow by around 26.4% worldwide to $195.57 billion between 2020 and 2027.
  • PPG supports diverse vital-sign monitoring: a smartwatch PPG/accelerometer algorithm detected atrial fibrillation with 98% sensitivity and 90.2% specificity, and PPG-based glucose estimation achieved maximum correlation coefficients of 0.91 and 0.86 with a standard prediction error of approximately 6.16 mg/dl.
  • Optical fiber and radiation sensors report high accuracy in selected studies: POF smart-bed sensors had absolute errors below 1 rpm and 2 bpm, FBG temperature sensors reached 150 pm/°C (almost 15 times higher than bare FBG), and indirect core body temperature evaluation achieved ±0.03 °C accuracy.
  • The review organizes the field into four areas—photoplethysmography, radiation sensors, fiber sensors, and biochemical analyzers—and concludes that optical sensors are highly preferred for wearable electronics and telemedicine, despite remaining technical and material limitations.

Methods

  • Narrative review of optical sensors and devices related to human physiology, identifying four main areas: photoplethysmography, radiation sensors, fiber sensors, and biochemical analyzers.
  • The paper synthesizes selected and promising sensor types and applications, with summary tables listing sensor type, application, sensing element, key parameters, and references.
  • No primary experimental sample, systematic search strategy, or quantitative meta-analysis is reported; findings are compiled from cited studies and commercial/technical examples.

Limitations

  • The paper states that ambient light interference, short penetration depth into skin and other bioliquids, sensor stability issues (especially electrochemical passivation and biofouling), optical fiber damage during use, uncertain nanomaterial biocompatibility/toxicity, flexible battery and energy-management needs, and patient-data privacy remain challenges.
  • Evident from the text: as a narrative review, it does not report a systematic search protocol, inclusion criteria, risk-of-bias assessment, or pooled quantitative synthesis.
  • Evident from the text: reported performance figures come from heterogeneous cited studies and devices, so they are not directly comparable or independently validated within this review.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3390/bios12040217

Cites

317 of 319 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 201 cited sources checked · 0 supported · 0 flagged

  • Premisecitation

    Microelectronic technologies may ultimately reach their limits inherent in low-frequency electromagnetic fields.

    “As microelectronic technologies are driven by requirements for wearable devices towards higher sensitivity, faster response, better robustness, and higher integration, they may ultimately reach their limits, which are inherent in the very nature of low-frequency electromagnetic fields [26,27,28,29,30,31].”
    Quote in the paperSubstantial claim0 of 6 sources checked
    • cites [26] Kang, 2014, Ultrasensitive mechanical crack-based sensor inspired by the spider sensory system, Nature source

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    • cites [27] Yin, 2016, Efficient and mechanically robust stretchable organic light-emitting devices by a laser-programmable buckling process, Nat. Commun. source

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    • cites [28] Miyamoto, 2017, Inflammation-free, gas-permeable, lightweight, stretchable on-skin electronics with nanomeshes, Nat. Nanotechnol. source

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    • cites [29] Takei, 2010, Nanowire active-matrix circuitry for low-voltage macroscale artificial skin, Nat. Mater. source

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    • cites [30] Larson, 2016, Highly stretchable electroluminescent skin for optical signaling and tactile sensing, Science source

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    • cites [31] Kim, 2018, A bioinspired flexible organic artificial afferent nerve, Science source

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  • Premisecitation

    Blood oxygenation is proportional to reflected red light (622-780 nm) and IR (780-2400 nm).

    “Blood oxygenation is proportional to reflected red light (622–780 nm) and IR (780–2400 nm) [87].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [87] Chang, C.C., Wu, C.T., Choi, B.I., and Fang, T.J. (2019). MW-PPG sensor: An on-chip spectrometer approach. Sensors, 19. source

      Not checked in the free run.

  • Premisecitation

    HR measurement can predict cardiovascular morbidity and mortality in a reliable and easily accessible way.

    “It can predict cardiovascular morbidity and mortality in a very reliable and easily accessible way.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [42] Ernst, 2017, Heart-Rate Variability—More than Heart Beats?, Front. Public Health source

      Not checked in the free run.

    • cites [43] Shaffer, 2017, An Overview of Heart Rate Variability Metrics and Norms, Front. Public Health source

      Not checked in the free run.

  • Premisecitation

    Efforts are made to measure BP based on pulse wave transition time (PTT) from PPG curve shape or time shift between ECG and PPG in periphery.

    “Thus, great efforts are made to measure BP based on the pulse wave transition time (PTT), whether from the shape of the PPG curve or the time shift between ECG and PPG in the periphery [44].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [44] Dias, D., and Paulo Silva Cunha, J. (2018). Wearable Health Devices—Vital Sign Monitoring, Systems and Technologies. Sensors, 18. source

      Not checked in the free run.

  • Premisereasoning

    To minimize artifacts, modern PPG chips include accelerometric sensors or multiple optical paths using two photodiodes.

    “To minimize these artifacts, accelerometric sensors or multiple optical paths using two photodiodes are therefore included in modern PPG chips.”
    Quote in the paperNot a substantial claim
  • May combine two claims. 67
  • Classified as probably not a substantial claim. 40

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    Premisecitation

    Optical sensors offer excellent metrological properties such as low zero and low sensitivity drift, good accuracy, sensitivity, and large usable bandwidth.

    “They propose excellent metrological properties such as low zero and low sensitivity drift, good accuracy, sensitivity, and large usable bandwidth [24].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [24] Hayward, J. (2022, January 26). Wearable Sensors 2021–2031. Available online: http://www.idtechex.com/en/research-report/wearable-sensors-2021-2031/780.

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Optical sensors are immune to electromagnetic interference and electrically safe.

    “They are immune to electromagnetic interference, electrically safe, can achieve outstanding miniaturization, and they are capable of capturing nanoscale volumes, allowing the non-invasive examination of biological matter with relatively large penetration depths.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] Rehg, J.M., Murphy, S.A., and Kumar, S. (2017). Wearable Optical Sensors. Mobile Health, Springer International Publishing. source

      Not checked in the free run.

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    Premisecitation

    Optical sensors can achieve outstanding miniaturization and capture nanoscale volumes, allowing non-invasive examination of biological matter with relatively large penetration depths.

    “They are immune to electromagnetic interference, electrically safe, can achieve outstanding miniaturization, and they are capable of capturing nanoscale volumes, allowing the non-invasive examination of biological matter with relatively large penetration depths.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] Rehg, J.M., Murphy, S.A., and Kumar, S. (2017). Wearable Optical Sensors. Mobile Health, Springer International Publishing. source

      Not checked in the free run.

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    Premisecitation

    Optical sensing elements are often inexpensive, water- and corrosion-resistant.

    “Sensing elements, whether in the form of optical fibers or optically transparent encapsulated photoplethysmographic and biochemical sensors, are often inexpensive, water- and corrosion-resistant [25].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [25] Rehg, J.M., Murphy, S.A., and Kumar, S. (2017). Wearable Optical Sensors. Mobile Health, Springer International Publishing. source

      Not checked in the free run.

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    Premisecitation

    The PPG signal recorded in a real environment often contains movement artifacts and is affected by changing pressure of sensor on skin.

    “The PPG signal, when recorded in a real environment, often contains movement artifacts and is also affected by the changing pressure of the sensor on the skin [80].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [80] Horton, 2017, Comparison of Polar M600 Optical Heart Rate and ECG Heart Rate during Exercise, Med. Sci. Sport. Exerc. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    A progressive method for RR measurement is algorithms extraction from captured PPG signal.

    “Today, a very progressive method is the algorithms’ extraction from the captured photoplethysmography signal.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    Changes in blood vessel walls due to HR can be easily and reliably detected by optical sensors, mostly PPG or optical fiber.

    “These changes can be easily and reliably detected by optical sensors, mostly PPG or optical fiber.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationnone given

    PPG technology is very successful but not fully reliable; limitations are in measurement standardization, setting regularizing ranges of data to correlate with patients, and evaluation of different treatment actions.

    “PPG technology is very successful but still not ideal. There are still challenges and improvements to be made. PPG is not fully reliable, the limitations are in the measurement’s standardization, the setting up of regularizing ranges of data to correlate with patients, and the evaluation of different treatment actions.”
    Quote in the paperNot a substantial claim

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    Premisecitation

    Low HRV indicates body is working hard, tired, dehydrated, stressed, or sick.

    “Low HRV indicates that the body is working hard, it is tired, dehydrated, stressed, or sick [42,43].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [42] Ernst, 2017, Heart-Rate Variability—More than Heart Beats?, Front. Public Health source

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    • cites [43] Shaffer, 2017, An Overview of Heart Rate Variability Metrics and Norms, Front. Public Health source

      Not checked in the free run.

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    Premisecitation

    HR measuring using PPG is well characterized and works seamlessly, but data processing for healthcare applications is large and requires considerable computing power and continuous energy supply.

    “HR measuring using PPG is well characterized and works seamlessly; however, we must take into account that the amount of data processing for healthcare applications is large and requires considerable computing power and continuous energy supply [11].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [11] Yetisen, 2018, Wearables in Medicine, Adv. Mater. source

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    Premisenone given

    Reflective PPG has lower signal quality but is more suitable for nonstop wearing.

    “This configuration has a lower signal quality, but it is more suitable for nonstop wearing.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    SpO2 provides information on lung efficiency and is an important indicator of overall human health.

    “The SpO2 provides information on lung efficiency and is an important indicator of overall human health.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Light in visible to NIR region can only reach human tissues to depth of a few millimeters, and penetration is limited by absorption by blood, melanin, fat, water, and light scattering.

    “Light in the spectrum from the visible to the near-infrared (NIR) region can only reach human tissues to a depth of a few millimeters, and its penetration is limited due to the absorption of light by blood, melanin, fat, water, and light scattering.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisenone given

    PPG is one of the most widely used optical imaging methods in healthcare, used to monitor blood flow in real-time.

    “In healthcare, one of the most widely used optical imaging methods is photoplethysmography (PPG) (Table 1), which is used to monitor blood flow in real-time.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Premisenone given

    The accuracy of home glucometers varies ±15%.

    “The accuracy of home glucometers also varies ±15%.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The non-pulsating component of PPG is a function of basal blood volume, respiration, sympathetic nervous system activity, and thermoregulation.

    “The pulsating component is related to changes in arterial blood volume and is synchronous with the heartbeat, while the non-pulsating component is a function of basal blood volume, respiration, sympathetic nervous system activity, and thermoregulation [54].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [54] Utami, N., Setiawan, A.W., Zakaria, H., Mengko, T.R., and Mengko, R. (2013, January 7–8). Extracting blood flow parameters from Photoplethysmograph signals: A review. Proceedings of the 2013 3rd International Conference on Instrumentation, Communications, Information Technology and Biomedical Engineering (ICICI-BME), Bandung, Indonesia. source

      Not checked in the free run.

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    Premisecitation

    Red light and NIR penetrate deeper into human body and provide a wider range of information about physiological signal.

    “On the contrary, red light and NIR penetrate deeper into the human body and thus provide a wider range of information about the physiological signal [55,56].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [55] Elgendi, 2019, The use of photoplethysmography for assessing hypertension, NPJ Digit. Med. source

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    • cites [56] Marzorati, 2020, Chest Wearable Apparatus for Cuffless Continuous Blood Pressure Measurements Based on PPG and PCG Signals, IEEE Access source

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  • May combine two claims.

    Premisecitation

    The pulsating component of PPG is related to changes in arterial blood volume and is synchronous with heartbeat.

    “The pulsating component is related to changes in arterial blood volume and is synchronous with the heartbeat, while the non-pulsating component is a function of basal blood volume, respiration, sympathetic nervous system activity, and thermoregulation [54].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [54] Utami, N., Setiawan, A.W., Zakaria, H., Mengko, T.R., and Mengko, R. (2013, January 7–8). Extracting blood flow parameters from Photoplethysmograph signals: A review. Proceedings of the 2013 3rd International Conference on Instrumentation, Communications, Information Technology and Biomedical Engineering (ICICI-BME), Bandung, Indonesia. source

      Not checked in the free run.

  • May combine two claims.

    Premisenone given

    Transmission PPG measurements are more stable, repetitive, and less sensitive to position changes.

    “Such measurements are more stable, repetitive, and less sensitive to position changes.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Monitoring processes in human body allows easier detection of vital signs such as HR, RR, blood pressure, allowing early rapid diagnosis and prevention.

    “Monitoring the processes in the human body allows easier detection of vital signs such as heart rate (HR), respiratory rate (RR), blood pressure, etc., allowing early rapid diagnosis and prevention to be performed, and generally helping people to monitor their physiological parameters and inform the doctor in case of change.”
    Quote in the paperNot a substantial claim

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    Premisecitation

    PPG is used to determine physiological parameters such as oxygen saturation, blood pressure, cardiac output, respiration, and to evaluate autonomic function, depth of anesthesia, and detection of peripheral vascular disease.

    “It is used to determine the physiological parameters such as oxygen saturation, blood pressure, cardiac output, respiration but also to evaluate autonomic function, depth of anesthesia, as well as detection of peripheral vascular disease [52].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [52] Shelley, 2007, Photoplethysmography: Beyond the Calculation of Arterial Oxygen Saturation and Heart Rate, Anesth. Analgesia source

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  • May combine two claims.

    Premisenone given

    Optical sensors offer a non-invasive method of continuous glucose measurement, unlike current glucometers requiring blood collection from a finger.

    “In this case, the sensors offer a non-invasive method of continuous measurement, unlike current glucometers, which require blood collection from a finger.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The PPG signal is a mixture of blood flow in veins and arteries and consists of a pulsating and non-pulsating component of blood volume.

    “The PPG signal is a mixture of blood flow in the veins and arteries and generally consists of a pulsating and non-pulsating component of the blood volume [53].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [53] Lee, 2011, Relations between ac-dc components and optical path length in photoplethysmography, J. Biomed. Opt. source

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    Premisecitation

    A photonic crystal that responds to glucose levels has been described; the sensor bends light and the diffracted band shifts as glucose concentration changes.

    “The development of optic sensors today focuses on the rapid, continuous and simple determination of glucose in surrounding body fluids, for example, the use of a photonic crystal that responds to glucose levels has been described, the sensor bends light, and the diffracted band shifts as the glucose concentration changes [47].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [47] Alexeev, 2004, Photonic crystal glucose-sensing material for noninvasive monitoring of glucose in tear fluid, Clin. Chem. source

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    Interpretationcitation

    Devices using NFC communication represent a promising version of HR monitors.

    “Devices using NFC communication represent a very promising version of HR monitors [85].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [85] Kang, M.H., Lee, G.J., and Yun, J.H. (2021). NFC-Based Wearable Optoelectronics Working with Smartphone Application for Untact Healthcare. Sensors, 21. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisereasoning

    Transmission PPG configuration uses LEDs and photodiode facing each other, light passes through tissue, measuring non-absorbed light.

    “If the light-emitting diodes (LEDs) and the photodiode (PD) are facing each other and the light passes through the tissue, where we measure the non-absorbed light, we speak of the transmission principle.”
    Quote in the paperNot a substantial claim

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    Premisereasoning

    Estimation of SpO2 is based on different spectral characteristics of hemoglobin and deoxyhemoglobin, thus two LEDs are used.

    “These measurements are similar to those using LEDs and PDs, but the estimation of SpO2 level is based on the different spectral characteristics of hemoglobin and deoxyhemoglobin, thus two LEDs are used.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    Optical sensors in medicine can be used to increase intelligence of medical equipment, implants, and to monitor human physiology remotely even without direct contact with patient.

    “They can be used to increase the intelligence of medical equipment, implants, and to monitor human physiology remotely even without direct contact with the patient.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    In many cases, optical sensors do not have to be in direct contact with the human body or do not require high quality of contact.

    “In many cases, the optical sensors do not even have to be in direct contact with the human body or do not require a high quality of contact.”
    Quote in the paperNot a substantial claim

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    Premisecitation

    Organic semiconductor devices have attractive properties including simple production on flexible substrates, miniaturization, simultaneous generation and detection of optical signal, and tunable light emission over a wide range.

    “Organic semiconductor devices have many attractive properties. These include simple production on flexible substrates, the possibility of miniaturization, the simultaneous ability to generate and detect an optical signal, and tunable light emission in a wide range of values [33,34,35].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [33] Sessolo, 2013, Easy-to-fabricate conducting polymer microelectrode arrays, Adv. Mater. source

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    • cites [34] Forrest, 2004, The path to ubiquitous and low-cost organic electronic appliances on plastic, Nature source

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    • cites [35] Li, 2012, Polymer solar cells, Nat. Photonics source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    High HRV indicates nervous system is balanced and body can adapt to environment and function well.

    “When the HRV is high, the nervous system is balanced, and the body can adapt to the environment and function well.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [42] Ernst, 2017, Heart-Rate Variability—More than Heart Beats?, Front. Public Health source

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    • cites [43] Shaffer, 2017, An Overview of Heart Rate Variability Metrics and Norms, Front. Public Health source

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    Premisecitation

    PDs and LEDs must be optically isolated, and the whole optical system must be surrounded by optical separation techniques to reduce ambient light impact.

    “PDs and the LEDs must be optically isolated [78], for example, using a raised mesa, and the whole optical system must be surrounded by optical separation techniques to reduce the impact of ambient light [79].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [78] Pateau, 2019, Photoplethysmographic determination of the respiratory rate in acutely ill patients: Validation of a new algorithm and implementation into a biomedical device, Ann. Intensive Care source

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    • cites [79] Li, 2019, The Current State of Mobile Phone Apps for Monitoring Heart Rate, Heart Rate Variability, and Atrial Fibrillation: Narrative Review, JMIR mHealth uHealth source

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    Premisecitation

    Tison's group used a PPG sensor and accelerometer of a commercial smartwatch to obtain HR data and steps; their device can detect atrial fibrillation with sensitivity 98% and specificity 90.2%.

    “Thanks to the algorithm based on heuristic pretraining and deep neural network training, their device can detect the fibrillation with sensitivity of 98% and specificity of 90.2% [83].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [83] Tison, 2018, Passive detection of atrial fibrillation using a commercially available smartwatch, JAMA Cardiol. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Today, about 15% of the market for wearable devices is based on optical sensors and this number is constantly growing.

    “Today, about 15% of the market for wearable devices is based on optical sensors and this number is constantly growing [24].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [24] Hayward, J. (2022, January 26). Wearable Sensors 2021–2031. Available online: http://www.idtechex.com/en/research-report/wearable-sensors-2021-2031/780.

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  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Literature mentions an "optical window" for wavelengths of 600 to 1300 nm.

    “In the literature is also mentioned an “optical window” for wavelengths of 600 to 1300 nm [57,58,59].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [57] Ash, 2017, Effect of wavelength and beam width on penetration in light-tissue interaction using computational methods, Lasers Med. Sci. source

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    • cites [58] Anderson, 1981, The optics of human skin, J. Invest. Dermatol. source

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    • cites [59] Young, 1997, Chromophores in human skin, Phys. Med. Biol. source

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  • May combine two claims.

    Premisecitation

    Breathing manifests in PPG in three ways: pulse wave amplitudes affected by blood vessel flexibility, variation in pulse shape, and decrease in intrathoracic pressure leading to increased venous return during inspiration.

    “Breathing manifests itself in PPG in three ways. Pulse wave amplitudes are affected by the blood vessel flexibility, the variation in pulse shape, and a decrease in intrathoracic pressure that leads to increased venous return during inspiration [96,97].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [96] Akbar, U., Akbari, A., Alinia, P., Amato, F., Amendola, S., Balaban, E., Beach, C., Bertschi, M., Braun, F., and Caldani, L. (2021). Wearable Sensors: Fundamentals, Implementation and Applications. Wearable Sensors, Elsevier.

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    • cites [97] Madhav, K.V., Ram, M.R., Krishna, E.H., Komalla, N.R., and Reddy, K.A. (2011, January 10–12). Estimation of respiration rate from ECG, BP and PPG signals using empirical mode decomposition. Proceedings of the 2011 IEEE International Instrumentation and Measurement Technology Conference, Hangzhou, China. source

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    Premisecitation

    A flexible battery-free PPG wireless NFC monitoring device incorporating SpO2, HR, and HRV can be mounted on a thumbnail or ear lobe.

    “A very promising design is the flexible concept (Figure 1a) [12], which incorporates advanced optoelectronic functions for PPG wireless NFC monitoring applications, including SpO2, HR, and HRV.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] Kim, 2017, Miniaturized Battery-Free Wireless Systems for Wearable Pulse Oximetry, Adv. Funct. Mater. source

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    Premisecitation

    Myosin protein in muscle sarcomeres has liquid crystalline properties and is responsible for anisotropic behavior of muscles.

    “The myosin protein in muscle sarcomeres has liquid crystalline properties and is responsible for the anisotropic behavior of muscles [39].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [39] Bansal, 2015, Wearable Organic Optoelectronic Sensors for Medicine, Adv. Mater. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Adhikari et al. developed a multi-wavelength transmission mode PPG method to monitor drug delivery and examined concentrations of therapeutic gold nanoparticles, quinine, and amphotericin B in mice with absorption peaks in 350-1100 nm range.

    “Adhikari et al. [125] developed a multi-wavelength transmission mode PPG method to monitor drug delivery. They examined the concentration of therapeutic gold nanoparticles, quinine, and amphotericin B in mice possessing absorption peaks in the 350–1100 nm range.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [125] Coté, G.L. (2014). Multi-Wavelength Pulse Plethysmography for Real-Time Drug Delivery Monitoring, SPIE.

      Not checked in the free run.

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    Premisecitation

    RR and amplitude of respiration can be extracted from PPG.

    “Therefore, we can extract the RR and amplitude of respiration [98,99,100].”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [98] Karlen, 2013, Multiparameter Respiratory Rate Estimation from the Photoplethysmogram, IEEE Trans. Biomed. Eng. source

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    • cites [99] Nemati, 2010, Data Fusion for Improved Respiration Rate Estimation, EURASIP J. Adv. Signal Process. source

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    • cites [100] Shokoueinejad, 2017, Sleep apnea: A review of diagnostic sensors, algorithms, and therapies, Physiol. Meas. source

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  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Premisenone given

    A thermal camera captures multiple points while a PIR sensor senses only one.

    “The only difference between a thermal camera and a PIR sensor is that a thermal camera captures multiple points while a PIR sensor senses only one.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The boundary between internal and peripheral body temperature is indeterminate and varies with ambient temperature.

    “Internal body temperature is different from the body temperature of peripherals such as limbs, and the boundary between them is indeterminate and varies with ambient temperature [134].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [134] Ogoina, 2011, Fever, fever patterns and diseases called “fever”—A review, J. Infect. Public Health source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Today, optical blood pressure monitoring is a complete tool that can be built into firmware or software, allowing continuous cuffless BP measurement for virtually any type of PPG sensor.

    “Today, optical blood pressure monitoring is a complete tool that can be built directly into the firmware or subsequent software, allowing it to be possible to continuously measure blood pressure without using a cuff for virtually any type of PPG sensor.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The cheapest form of radiation sensor is a passive infrared (PIR) sensor used in handheld non-contact thermometers.

    “The cheapest form is a passive infrared (PIR) sensor used in handheld non-contact thermometers [131].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [131] Fang, 2006, Path-dependent human identification using a pyroelectric infrared sensor and fresnel lens arrays, Opt. Express source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Some researchers identified that orange and green lights perform better for SpO2 because of resistance to motion artifacts.

    “However, some researchers have identified that orange and green lights perform better because of their resistance to motion artifacts [88,89].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [88] Raghavachari, R., Liang, R., and Pfefer, T.J. (2018). An applicable approach for extracting human heart rate and oxygen saturation during physical movements using a multi-wavelength illumination optoelectronic sensor system. Proceedings of the Design and Quality for Biomedical Technologies XI, SPIE.

      Not checked in the free run.

    • cites [89] Alharbi, S., Hu, S., Mulvaney, D., Barrett, L., Yan, L., Blanos, P., Elsahar, Y., and Adema, S. (2018). Oxygen Saturation Measurements from Green and Orange Illuminations of Multi-Wavelength Optoelectronic Patch Sensors. Sensors, 19. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Polat et al. designed a flexible NFC patch to record HR, SpO2, and respiration, with a photodiode based on graphene sensitized with semiconducting quantum dots.

    “A similar flexible device was presented by Polat et al. [90], who designed a patch to record HR, SpO2, and respiration. Again, the communication is via NFC, but the photodiode in this case is based on graphene sensitized with semiconducting quantum dots.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [90] Polat, 2019, Flexible graphene photodetectors for wearable fitness monitoring, Sci. Adv. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Radiation sensors are popularly used to detect body temperature in association with infectious diseases.

    “Nowadays, radiation sensors are popularly used to detect body temperature in association with infectious diseases [129,130].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [129] Hussain, 2021, Proper use of noncontact infrared thermometry for temperature screening during COVID-19, Sci. Rep. source

      Not checked in the free run.

    • cites [130] Yu, W.L., Wang, Z., and Jin, L. (2012, January 5–7). The experiment study on infrared radiation spectrum of human body. Proceedings of the Proceedings of 2012 IEEE-EMBS International Conference on Biomedical and Health Informatics BHI 2012, Hong Kong, China. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The achieved maximum correlation coefficient of blood glucose determination is 0.91 and 0.86, respectively, representing a standard prediction error of approximately 6.16 mg/dl.

    “The achieved maximum correlation coefficient of blood glucose determination is 0.91 and 0.86, respectively, which represents a standard prediction error of approximately 6.16 mg/dl.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Core body temperature is lower in the early morning and has its greatest increase in the afternoon, with up to a 1 °C difference.

    “In the early morning, the temperature is lower with the greatest increase in the afternoon, which can be up to a 1 °C difference [135,136,137,138,139,140].”
    Quote in the paperNot a substantial claim0 of 6 sources checked
    • cites [135] Costa, 2018, Daily rhythm of skin temperature of women evaluated by infrared thermal imaging, J. Therm. Biol. source

      Not checked in the free run.

    • cites [136] Baschieri, 2021, Circadian and state-dependent core body temperature in people with spinal cord injury, Spinal Cord source

      Not checked in the free run.

    • cites [137] Baker, 2007, Circadian rhythms, sleep, and the menstrual cycle, Sleep Med. source

      Not checked in the free run.

    • cites [138] Honma, 2013, [Circadian rhythms in body temperature and sleep], Nihon Rinsho.

      Not checked in the free run.

    • cites [139] Edwards, 2009, Zeitgeber-effects of exercise on human circadian rhythms: What are alternative approaches to investigating the existence of a phase-response curve to exercise?, Biol. Rhythm Res. source

      Not checked in the free run.

    • cites [140] Chen, 2019, Thermometry and interpretation of body temperature, Biomed. Eng. Lett. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Thermal cameras have a spectral range of 7.5-14 μm.

    “This spectral range is almost identical to thermal cameras, where it is in the range of 7.5–14 μm [146].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [146] Bernard, 2013, Infrared camera assessment of skin surface temperature—Effect of emissivity, Phys. Medica source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    PPGI and IRTI allow long-term monitoring or monitoring of effects with special local characteristics.

    “Hence, these methods allow long-term monitoring or monitoring of effects with special local characteristics [189].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [189] Blanik, 2014, Hybrid optical imaging technology for long-term remote monitoring of skin perfusion and temperature behavior, J. Biomed. Opt. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    PPGI measurements can determine HR, HRV, RR, respiratory variability (RV), and vasomotion activity.

    “From PPGI measurements, the algorithm can determine HR, HRV, RR, respiratory variability (RV), and vasomotion activity.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [189] Blanik, 2014, Hybrid optical imaging technology for long-term remote monitoring of skin perfusion and temperature behavior, J. Biomed. Opt. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    PDMS HR and RR sensors with frequency-domain signal processing and filters achieve errors below 4 bpm and 2 rpm, applicable in ballistocardiography in different areas of the human body.

    “Applications in smart textiles such as HR and RR PDMS sensors with a focus on signal processing and analysis in the frequency domain and the application of various filters in research offers errors below 4 bpm and 2 rpm (respiration per minute) with good accuracy applicable in ballistocardiography in different areas of the human body [214].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [214] Leal-Junior, A.G., Diaz, C.A.R., Avellar, L.M., Pontes, M.J., Marques, C., and Frizera, A. (2019). Polymer optical fiber sensors in healthcare applications: A comprehensive review. Sensors, 19. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Thermal cameras can be used for photoplethysmography imaging (PPGI) and infrared thermographic imaging (IRTI) for contactless measurement of a wide range of basic vital parameters.

    “Thermal cameras can also be used for photoplethysmography imaging (PPGI) and infrared thermographic imaging (IRTI), where contactless measurement of a wide range of basic vital parameters is performed.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [189] Blanik, 2014, Hybrid optical imaging technology for long-term remote monitoring of skin perfusion and temperature behavior, J. Biomed. Opt. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Infrared thermometers can be classified as wearable devices due to their compactness.

    “Due to infrared thermometers’ compactness, these devices can be classified as wearable devices [158].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [158] Tamura, 2017, Body temperature, heat flow and evaporation, Seamless Healthc. Monit. Adv. Wearable Attach. Invis. Devices

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    A POF embedded in mattresses can measure respiration and HR to monitor sleep performance, tested on 10 subjects.

    “First, a POF is embedded in mattresses to measure respiration and HR to monitor sleep performance, which was tested on 10 subjects [219].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [219] Han, 2021, Low-cost plastic optical fiber sensor embedded in mattress for sleep performance monitoring, Opt. Fiber Technol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Optical fibers can monitor human vital signs such as respiration, cardiac activity, blood pressure and flow, oxygen saturation, shear stress, mobility, gait, temperature, and electrolyte balance.

    “Optical fibers can function as inconspicuous flexible systems monitoring human vital signs such as respiration, cardiac activity, blood pressure and flow, oxygen saturation, shear stress, mobility, gait, temperature, and electrolyte balance.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [201] Massaroni, C., Saccomandi, P., and Schena, E. (2015). Medical Smart Textiles Based on Fiber Optic Technology: An Overview. J. Funct. Biomater., 6. source

      Not checked in the free run.

    • cites [202] Trung, 2018, Freestanding, Fiber-Based, Wearable Temperature Sensor with Tunable Thermal Index for Healthcare Monitoring, Adv. Healthc. Mater. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    POFs embroidered into a moisture-wicking fabric can detect early changes in skin perfusion, oxygen saturation, HR, blood flow, and pressure on tissue for pressure ulcer prevention.

    “Research on the prevention of pressure ulcers in sensitive skin conditions that can detect early changes in skin perfusion, oxygen saturation, HR, blood flow, and pressure on the tissue, and subsequent therapeutic intervention in which POFs are embroidered into a moisture-wicking fabric appears to be very advanced [222].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [222] Quandt, 2017, Body-monitoring with photonic textiles: A reflective heartbeat sensor based on polymer optical fibres, J. R. Soc. Interface

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The POF mattress sensor has an absolute error less than 1 rpm and 2 bpm.

    “Its absolute error was less than 1 rpm and 2 bpm.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [219] Han, 2021, Low-cost plastic optical fiber sensor embedded in mattress for sleep performance monitoring, Opt. Fiber Technol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Nanoimprinted meta-surfaces consist of a 20 nm aluminum film buried in a thin-film polymer that is flexible, economical, and recyclable.

    “Nanoimprinted meta-surfaces consist of a 20 nm aluminum film buried in a thin-film polymer that is flexible, economical, and recyclable [283].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [283] Asger, 2016, Plasmonic colour laser printing, Nat. Nanotechnol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In wearable electronics, analyses of sweat, saliva, and tears are mainly performed, and pH, lactate, glucose, Na+, Cl−, Ca2+, Zn2+, and other chemical elements are detected.

    “In the field of wearable electronics the analyses of sweat, saliva, and tears are mainly performed and in addition to recording their amount, the pH, lactate, glucose, Na+, Cl−, Ca2+, Zn2+, and other chemical elements are detected [276].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [276] Zhu, D., Liu, B., and Wei, G. (2021). Two-dimensional material-based colorimetric biosensors: A review. Biosensors, 11. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    FBGs encapsulated inside PDMS can work as a multichannel sensor for body temperature, RR, and HR estimation or for evaluation of cardiac functions from carotid HR waveform.

    “FBGs encapsulated inside PDMS can work as a multichannel sensor for body temperature, RR, and HR estimation [253], or evaluation of the cardiac functions from carotid HR waveform [254].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [253] Fajkus, M., Nedoma, J., Martinek, R., Vasinek, V., Nazeran, H., and Siska, P. (2017). A non-invasive multichannel hybrid fiber-optic sensor system for vital sign monitoring. Sensors, 17. source

      Not checked in the free run.

    • cites [254] Padma, 2018, Carotid Arterial Pulse Waveform Measurements Using Fiber Bragg Grating Pulse Probe, IEEE J. Biomed. Health Inform. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Meta-surfaces as structural color can achieve strong static or dynamic colorimetry and are tunable by external stimuli such as mechanical stress, temperature change, electrical voltage, and optical excitation.

    “Meta-surfaces as a „structural color” can achieve strong static or dynamic colorimetry. These are tunable by external stimuli, such as mechanical stress, temperature change, electrical voltage, and optical excitation [288].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [288] Dong, 2021, Nanophotonic Structural Colors, ACS Photonics source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A 3D skin temperature mapping method based on an improved neural network genetic algorithm-back propagation has an absolute error of 0.11 °C.

    “The method for 3D skin temperature mapping based on an improved neural network genetic algorithm-back propagation with an absolute error of 0.11 °C is also interesting [248].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [248] Liu, 2019, An Optical Fiber-Based Data-Driven Method for Human Skin Temperature 3-D Mapping, IEEE J. Biomed. Health Inform. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    Colorimetry is suitable for many photo-medical applications and biomarker detections including electrolytes, small molecules, and proteins.

    “Colorimetry is suitable for many photo-medical applications and biomarker detections including electrolytes, small molecules, and proteins.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    All wearable biochemical sensors have limitations such as frequent calibration, readout drift due to biofouling, and biweekly sensor replacement.

    “All wearable biochemical sensors have some limitations, such as frequent calibration, readout drift due to biofouling, and biweekly sensor replacement [11].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [11] Yetisen, 2018, Wearables in Medicine, Adv. Mater. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    FBG technology has simple manufacturing, relatively strong signal reflection, resistance to optical signal intensity modulation, and excellent multiplexing and self-referencing capabilities allowing addressing of multiple sensors with a single optical cable.

    “FBG technology is one of the most admired options due to its simple manufacturing, relatively strong signal reflection, and resistance to optical signal intensity modulation, which is possible due to their spectral coding, as well as excellent multiplexing and self-referencing capabilities allowing addressing of multiple sensors with a single optical cable [243].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [243] Majumder, 2008, Fibre Bragg gratings in structural health monitoring—Present status and applications, Sens. Actuators A Phys. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Fabry-Perot sensors based on ethyl alpha cyanoacrylate fibers are used to monitor HR.

    “Applications are also known where Fabry–Perot sensors based on ethyl alpha cyanoacrylate fibers are used to monitor HR [239].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [239] Li, 2021, Heart-Rate Monitoring with an Ethyl Alpha-Cyanoacrylate Based Fiber Fabry-Perot Sensor, IEEE J. Sel. Top. Quantum Electron.

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    A miniature MRI-compatible multi-sensor offers a temperature accuracy of ±0.22 °C, a pressure resolution of 1 mmHg, and a localization resolution of 3 mm.

    “The miniature sensor offers a temperature accuracy of ±0.22 °C, a pressure resolution of 1 mmHg, and a localization resolution of 3 mm.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [275] Zolfaghari, 2021, MRI Compatible Fiber Optic Multi Sensor Platform for Real Time Vital Monitoring, J. Light. Technol. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    FBG sensors are small, portable, yarn compatible, easy to weave into fabrics, and have become the most promising material for sensing elements in intelligent clothing.

    “FBG sensors are small, portable, yarn compatible, and easy to weave into fabrics, and have become the most promising material for sensing elements in creating intelligent clothing [242,244,245].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [242] Sahota, 2020, Fiber Bragg grating sensors for monitoring of physical parameters: A comprehensive review, Opt. Eng. source

      Not checked in the free run.

    • cites [244] Li, 2016, Review of the Strain Modulation Methods Used in Fiber Bragg Grating Sensors, J. Sens. source

      Not checked in the free run.

    • cites [245] Campanella, C.E., Cuccovillo, A., Campanella, C., Yurt, A., and Passaro, V.M.N. (2018). Fibre Bragg Grating based strain sensors: Review of technology and applications. Sensors, 18. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    A dimer-like silicon-based single nanoantenna produces both high surface enhanced fluorescence and surface enhanced Raman scattering while generating a negligible temperature increase in its hot spots and surrounding environment.

    “Dimer-like silicon-based single nanoantenna produces both high surface enhanced fluorescence and surface enhanced Raman scattering, while generating a negligible temperature increase in their hot spots and surrounding environment at the same time [289,290].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [289] Caldarola, 2015, Non-plasmonic nanoantennas for surface enhanced spectroscopies with ultra-low heat conversion, Nat. Commun. source

      Not checked in the free run.

    • cites [290] Dong, 2021, Silicon Nanoantenna Mix Arrays for a Trifecta of Quantum Emitter Enhancements, Nano Lett. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationnone given

    Compared to amperometric devices, colorimetric, fluorescence and luminescence sensors have the advantages of simple structure, low cost, and portable design usually without power operation.

    “Compared to amperometric devices, colorimetric, fluorescence and luminescence sensors have the advantages of simple structure, low cost, and portable design usually without power operation.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    An FBG sensor used for radial artery pulse waveform measurement achieved a sensitivity of 8.236 nm/N.

    “Jia et al. [252] used an FBG sensor for the radial artery pulse waveform measurement and achieved a sensitivity of 8.236 nm/N.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [252] Jia, 2018, A Fiber Bragg Grating Sensor for Radial Artery Pulse Waveform Measurement, IEEE Trans. Biomed. Eng. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing). May combine two claims.

    Premisecitation

    A plate FBG sensor mounted inside a seat cushion can monitor HR with a maximum error of ±3 bpm and RR with ±1.2 rpm.

    “In the next research, the plate FBG sensor is mounted inside the cushion, which is on the back of the seat and HR monitoring with a maximum error of ±3 bpm and RR with ±1.2 rpm is possible [262].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [262] Dziuda, 2013, Fiber Bragg grating-based sensor for monitoring respiration and heart activity during magnetic resonance imaging examinations, J. Biomed. Opt. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    These materials and structures can be used as cost-effective colorimetric chemical detection devices for biochemical analysis methods or can substitute expensive spectrometers.

    “These materials and structures can be used as cost-effective colorimetric chemical detection devices for biochemical analysis methods or can substitute expensive spectrometers [287].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [287] Ho, 2019, Tunable, Cost-Effective, and Scalable Structural Colors for Sensing and Consumer Products, Adv. Opt. Mater. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    A double-stranded Bragg grating wearable system monitors neck movements and breathing activity, and when tested on five subjects, RR was monitored with percentage errors of ≤6.09% and ≤1.90% during silent tachypnea breathing.

    “Another multiparametric wearable system based on a double-stranded Bragg grating is monitoring neck movements and breathing activity [267]. The sensing elements were placed on the neck, in the frontal and sagittal planes. The system was tested on five subjects and RR was monitored with percentage errors of ≤6.09% and ≤1.90%, during silent tachypnea breathing.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [267] Presti, D.L., Carnevale, A., D’Abbraccio, J., Massari, L., Massaroni, C., Sabbadini, R., Zaltieri, M., Di Tocco, J., Bravi, M., and Miccinilli, S. (2020). A multi-parametric wearable system to monitor neck movements and respiratory frequency of computer workers. Sensors, 20. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationnone given

    Fluorescence analysis provides short response times, minimal instrumentation requirements, and overall low cost.

    “Fluorescence analysis provides short response times, minimal instrumentation requirements, and overall low cost.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    Optical sensors are widely usable in various types of devices for measuring a wide range of physiological parameters.

    “It is obvious that optical sensors are widely usable in various types of devices for measuring a wide range of physiological parameters.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Compared to colorimetry, fluorescence-based protein assays have advantages such as rapid assay time, higher stability, better detection sensitivity, and can examine multiple analytes simultaneously.

    “Compared to colorimetry, fluorescence-based protein assays have advantages such as rapid assay time, higher stability, better detection sensitivity, and can examine multiple analytes simultaneously [316].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [316] Singh, M., Truong, J., Reeves, W.B., and Hahm, J.I. (2017). Emerging cytokine biosensors with optical detection modalities and nanomaterial-enabled signal enhancement. Sensors, 17. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Athletes have improved their performance through the use of optical sensors.

    “For example, athletes have improved their performance [332].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [332] Koydemir, 2018, Wearable and Implantable Sensors for Biomedical Applications, Annu. Rev. Anal. Chem. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    The use of optical sensors can help reduce healthcare costs through the continuous monitoring of physiologically important parameters.

    “The use of optical sensors can help reduce healthcare costs through the continuous monitoring of physiologically important parameters.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    Nanomaterials may be a suitable component of flexible sensors and increase scanning performance, but it is still not entirely clear whether they are completely biocompatible and non-toxic to cells.

    “Nanomaterials may also be a suitable component of flexible sensors and increase scanning performance, but it is still not entirely clear whether they are completely biocompatible and non-toxic to cells [203].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [203] Hatamie, 2020, Review—Textile Based Chemical and Physical Sensors for Healthcare Monitoring Review—Textile Based Chemical and Physical Sensors for Healthcare Monitoring, J. Electrochem. Soc. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    A general challenge of using optical fiber sensors is damage of the system while locating it in the field or within its working lifetime, which must be controlled and requires further research.

    “On the other hand, a general challenge of using optical fiber sensors could be damage of the system while locating it in the field or within its working lifetime which must be controlled and requires further research in this area [331].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [331] Ferreira, 2017, Roadmap on optical sensors, J. Opt. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationcitation

    Ultimately, all research leads to more stable, accurate, robust sensing mechanisms and components that will withstand long-term use.

    “Ultimately, all research leads to more stable, accurate, robust sensing mechanisms and components that will withstand long-term use [203].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [203] Hatamie, 2020, Review—Textile Based Chemical and Physical Sensors for Healthcare Monitoring Review—Textile Based Chemical and Physical Sensors for Healthcare Monitoring, J. Electrochem. Soc. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    The main disadvantage of colorimetry is that colorimetric tests exist only for a relatively narrow range of biomarkers.

    “The main disadvantage of colorimetry is that colorimetric tests exist only for a relatively narrow range of biomarkers.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationnone given

    Interference of ambient light with signal measurements and short penetration depth into the skin and other bioliquids are drawbacks of optical bio-sensors that limit their widespread use in the biosensing area.

    “However, the interference of ambient light with signal measurements, the short penetration depth into the skin and other bioliquids are some of the drawbacks of optical bio-sensors that limit their widespread use in the biosensing area.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S4 (based). May combine two claims.

    Interpretationnone given

    Due to their many benefits, optical sensors are highly preferred in wearable electronics and are the future of telemedicine.

    “Due to their many benefits, they are highly preferred in wearable electronics and are the future of telemedicine.”
    Quote in the paperNot a substantial claim
87 of 87

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Mattress and pediatric fiber-sensor references are swapped

    Minor

    The prose assigns the macrobending mat to [226] and the pediatric microbending sensor to [227]. Table 3 assigns those applications the opposite references.

  • Study [269] is described as two different sensor applications

    Minor

    The prose says Xiang et al. [269] studied pressure in a pneumatic compression device, whereas Table 3 labels [269] a nasal-airflow sensor.

  • Reference [314] is attributed to incompatible studies

    Minor

    One passage attributes [314] to Ozcan's urine-albumin device; another attributes it to Lim et al.'s transcutaneous oxygen-pressure sensor.

  • Patch [304] measures sweat in the prose but wounds in the table

    Minor

    The prose identifies the [304] hydrogel patch as a sweat detector; Table 4 describes the same patch's analytes as being measured in wounds.

  • Humidity-sensor response is given as milliseconds and meters

    Minor

    For the same [274] sensor, the prose reports a response time of about 42 ms, while Table 3 reports "42 m," a length rather than a time.

  • T-shirt has two FBGs in the prose but three in Table 3

    Minor

    The prose describes the T-shirt sensors, including [249], as having two FBGs; the Table 3 entry for [249] says three.

6 of 6

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. Reşit Kavsaoglu, A., Polat, K., Recep Bozkure, M., and Muthusamy, H. (2013, January 24–26). Fotopletismografi sinyalleri ile biyometrik tanlmaya yönelik özellilk çlkarlml. Proceedings of the 2013 21st Signal Processing and Communications Applications Conference (SIU), Haspolat, Turkey.
  2. Ghosh, 2005, Development of a sensor-embedded flexible textile structure for apparel or large area applications, Indian J. Fibre Text. Res., 30, 42

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Authors
Vavrinsky, E., Esfahani, N. E., Hausner, M., Kuzma, A., Rezo, V., Donoval, M., & Kosnacova, H.
Affiliations
  • Institute of Electronics and Photonics, Faculty of Electrical Engineering and Information Technology, Slovak University of Technology, Ilkovicova 3, 81219 Bratislava, Slovakia
  • Slovak University of Technology in Bratislava (SK)
  • Slovak Academy of Sciences (SK)
Corresponding author
Kosnacova, Helena
ORCID
Venue
Biosensors
Publisher
MDPI AG
Published
2022-04-06
Volume
12
Issue
4
Pages
217
ISSN
2079-6374 (ISSN-L)
DOI
10.3390/bios12040217
PMC
PMC9029995
OpenAlex
W4224239721
Semantic Scholar
946af75b40694a578b46260de186850ec58e590b
Cited by
103
References
317
Citations by year
2026: 21 · 2025: 26 · 2024: 28 · 2023: 23 · 2022: 5
FWCI
1.83
Type
journal article
Language
en
Open access
Licence
Locations
  • Biosensors (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
Research Agency of the Slovak Republic (ITMS code: 313011ASY8)
Topics
  • Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
  • Health Sciences › Medicine › Radiology, Nuclear Medicine and Imaging › Optical Imaging and Spectroscopy Techniques
  • Physical Sciences › Chemical Engineering › Bioengineering › Analytical Chemistry and Sensors
Keywords
optical sensors, wearable medical devices, photoplethysmography, fiber optic sensors, biochemical sensors, radiation detectors, non-invasive physiological monitoring, telemedicine, home health monitoring, wearable biosensors
MeSH terms
Wearable Electronic Devices, Humans, Technology, Telemedicine, Optical Fibers

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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