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Cited by 861Advanced Sensor and Energy Harvesting MaterialsElectrochemical sensors and biosensorsNon-Invasive Vital Sign Monitoring

A wearable chemical–electrophysiological hybrid biosensing system for real-time health and fitness monitoring

Open access
Imani, Somayeh, Bandodkar, Amay J., Mohan, A. M. Vinu, Kumar, Rajan, Yu, Shengfei, Wang, Joseph, Mercier, Patrick P.·2016·Nature Communications
DOI 10.1038/ncomms11650PMC PMC4879240
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Abstract

Flexible, wearable sensing devices can yield important information about the underlying physiology of a human subject for applications in real-time health and fitness monitoring. Despite significant progress in the fabrication of flexible biosensors that naturally comply with the epidermis, most designs measure only a small number of physical or electrophysiological parameters, and neglect the rich chemical information available from biomarkers. Here, we introduce a skin-worn wearable hybrid sensing system that offers simultaneous real-time monitoring of a biochemical (lactate) and an electrophysiological signal (electrocardiogram), for more comprehensive fitness monitoring than from physical or electrophysiological sensors alone. The two sensing modalities, comprising a three-electrode amperometric lactate biosensor and a bipolar electrocardiogram sensor, are co-fabricated on a flexible substrate and mounted on the skin. Human experiments reveal that physiochemistry and electrophysiology can be measured simultaneously with negligible cross-talk, enabling a new class of hybrid sensing devices.

AI snapshot

Written from the paper’s full text.

TL;DR

A screen-printed, skin-worn hybrid patch simultaneously measures sweat lactate and electrocardiogram (ECG) with negligible cross-talk. In three healthy male subjects during cycling, ECG-derived heart rate correlated strongly with a commercial monitor, and lactate response tracked exertion.

Key findings

  • The Chem–Phys patch combined a three-electrode amperometric lactate biosensor and bipolar ECG electrodes on a 50-μm polyester sheet; the full patch was 7 × 2 cm², with 1.5 × 1.5 cm² ECG electrodes separated by 4 cm and lactate electrodes of 3 × 2.5 mm active area.
  • In vitro, the lactate biosensor responded linearly from 0–28 mM with a sensitivity of 96 nA/mM; human sweat lactate typically ranges from 0–25 mM.
  • In three healthy male subjects during 15–30 min of intense cycling, ECG and lactate were measured simultaneously with negligible co-interference; heart rate extracted from the patch matched a commercial wristband monitor with Pearson’s r = 0.975.
  • An enzyme-free control amperometric sensor produced negligible current under the same conditions, supporting selectivity of the LOx-based lactate sensor.

Methods

  • The hybrid patch was fabricated by screen-printing Ag/AgCl, Prussian blue, and insulator inks on flexible polyester; the lactate working electrode was functionalized with lactate oxidase and coated with polyvinyl chloride, and a printed hydrophobic Ecoflex layer separated the amperometric and ECG electrodes.
  • The patch interfaced with a custom 4-layer PCB containing a potentiostat, ECG analog front-end, and Bluetooth low-energy radio; in vitro lactate characterization used 0.1 M phosphate-buffered solution (pH 7.0) at −0.1 V versus Ag/AgCl for 60 s.
  • Human testing involved 3 healthy male volunteers with no prior heart conditions, diabetes, or chronic skeletomuscular pain; the patch was placed on the fourth intercostal space between V1 and V2, and subjects cycled on a stationary bicycle with increasing resistance every 3 min followed by a 3-min cool-down.

Limitations

  • The paper does not include a dedicated limitations section; it describes the device as “an important first step” and states that all relevant data are available from the authors on request.
  • Evident from the text: the human validation was very small (3 healthy male volunteers) and short-term (15–30 min exercise bouts), with no female, clinical, or broader-population testing.
  • Evident from the text: the study did not assess long-term wear, repeated use, or multi-day stability, and lactate was measured in sweat rather than blood.

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

Integrity signals

Registry

Crossref · 10.1038/ncomms11650

Cites

54 of 54 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 10 cited sources checked · 0 supported · 0 flagged

  • Findingreasoning

    The hydrophobic barrier between the lactate and ECG sensors assisted in minimizing potential cross-talk between the two sensing modalities.

    “These on-body studies illustrate that the hybrid patch could monitor sweat lactate and electrocardiogram in a continuous and simultaneous manner, and that the hydrophobic barrier between the sensors assisted in minimizing potential cross-talk between the two sensing modalities.”
    • Also stated in: § Hybrid patch design rationale and fabrication · plain
      “This effectively increases the impedance between the electrocardiogram and amperometric electrodes via sweat, thus minimizing the cross-talk between the two sensors.”
    Quote in the paperSubstantial claim
  • Findingown data

    Heart rate extracted from the Chem-Phys patch ECG data matched a commercial wristband heart rate monitor with a Pearson's correlation coefficient of r=0.975.

    “Extracted heart rate data matched the wrist-worn device with a Pearson's correlation coefficient of r=0.975.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The commercial wristband heart rate monitor (BASIS) provides an accurate heart rate reference.
  • Findingown data

    The hydrophobic barrier had minimal effect on the supply of oxygen to the enzyme electrode required for biocatalytic detection of lactate.

    “The data also demonstrates that such a barrier had minimal effect on the supply of oxygen to the enzyme electrode required for biocatalytic detection of lactate.”
    Quote in the paperSubstantial claim
  • Findingown data

    On-body ECG signals recorded using the fabricated electrodes have similar morphologies to those recorded using commercial 3M Red Dot ECG electrodes at the same location with the same AFE circuitry.

    “As illustrated in Fig. 2b, on-body electrocardiogram signals recorded for the same subject using commercial and fabricated electrodes at the same location have similar morphologies when acquired using the same AFE circuitry.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The commercially available 3M Red Dot ECG electrodes provide a valid reference for ECG morphology.
  • Findingown data

    Physiochemistry and electrophysiology can be measured simultaneously with negligible cross-talk.

    “Human experiments reveal that physiochemistry and electrophysiology can be measured simultaneously with negligible cross-talk, enabling a new class of hybrid sensing devices.”
    • Also stated in: § Epidermal evaluation of the Chem–Phys patch · hedged
      “These on-body studies illustrate that the hybrid patch could monitor sweat lactate and electrocardiogram in a continuous and simultaneous manner, and that the hydrophobic barrier between the sensors assisted in minimizing potential cross-talk between the two sensing modalities.”
    Quote in the paperSubstantial claim
  • May combine two claims. 10
  • Classified as probably not a substantial claim. 5

  • May combine two claims.

    Findingown data

    The lactate biosensor responds linearly to lactate concentrations in the physiological range of 0-28 mM with a sensitivity of 96 nA/mM.

    “Figure 2a shows the amperometric response of the lactate biosensor to increasing lactate concentrations in the physiological range of 0–28 mM. It is evidenced from this figure that the biosensor responds linearly to the lactate concentrations in this range with a sensitivity of 96 nA/mM.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    An enzyme-free (LOx-free) amperometric sensor produces a negligible current response under the same experimental conditions, confirming the lactate biosensor's high selectivity for lactate.

    “As shown in Fig. 4e, the control biosensor leads to a negligible current response without the presence of LOx, confirming the high selectivity of the lactate biosensor.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    During intense cycling, sweat-lactate concentration increases with increasing cycling resistance and correlates with physical exertion and heart rate, after a physiologic time delay.

    “As the resistance increases, the sweat-lactate concentration too increases, as illustrated in Fig. 4a–c, showing a correlation between physical exertion, heart rate and, after a physiologic time delay, lactate generation.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The increasing cycling resistance protocol invokes anaerobic metabolism at similar time scales, augmenting lactate excretion in perspiration.

  • May combine two claims.

    Premisecitation

    The chest region has a high sweat rate during physical exertion and can serve as an appropriate location to measure lactate levels in human perspiration.

    “The chest region is not only convenient for measurement of electrocardiogram, but also has a high-sweat rate during physical excursion4950, and can thus serve as an appropriate location to also measure lactate levels in human perspiration.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [4950]

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Lactate concentration in human sweat depends on a person's metabolism and level of exertion and typically ranges from 0 to 25 mM.

    “Lactate concentration in human sweat depends on a person's metabolism and level of exertion, and typically ranges from 0 to 25 mM (ref. 52).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [52] Green, J. M., Pritchett, R. C., Crews, T. R., McLester, J. R. & Tucker, D. C. Sweat lactate response between males with high and low aerobic fitness. Eur. J. Appl. Physiol. 91, 1–6 (2004). source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Chemical information can be conventionally acquired via clinical labs or point-of-care devices, but such approaches do not support continuous, real-time measurements.

    “Chemical information can be conventionally acquired via clinical labs or point-of-care devices323334; unfortunately, such approaches do not support continuous, real-time measurements, therefore limiting their utility to applications where stationary, infrequent tests are sufficient.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites 323334

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Gao et al. demonstrated a wearable patch that can simultaneously track levels of metabolites and electrolytes in human sweat, but electrophysiology sensors were not included.

    “Recently, Gao et al.41 demonstrated a wearable patch that can simultaneously track levels of metabolites and electrolytes in human sweat. However, electrophysiology sensors were not included, and such multimodal sensor fusion is crucial to obtain a more comprehensive knowledge about a wearer's well-being.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [41] Gao, W. et al. Fully integrated wearable sensor arrays for multiplexed in situ perspiration analysis. Nature 529, 509–514 (2016). source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Sweat lactate can be used to track an individual's performance and exertion level and is an important biomarker for tissue oxygenation and pressure ischaemia.

    “When used in physical-exertion monitoring, electrocardiogram measurements can help monitor heart health and function, while sweat lactate can be used to track an individual's performance and exertion level, and is also an important biomarker for tissue oxygenation and pressure ischaemia424344454647.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites 424344454647

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Recent epidermal electronic devices can measure chemicals such as electrolytes and metabolites continuously on the skin or through non-invasive monitoring of other body fluids, but these devices measure only a single parameter at once and are not integrated with other sensing modalities.

    “While recent work, including our own, has demonstrated that chemicals such as electrolytes and metabolites can be measured continuously using epidermal electronics on the skin35363738, or through non-invasive monitoring of other body fluids383940, these devices measure only a single parameter at once, and are not integrated with other sensing modalities.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites 35363738

      Not checked in the free run.

    • cites 383940

      Not checked in the free run.

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

    Study design and conductown data

    Informed signed consent was obtained from each individual following a rigorous prescreening procedure.

    “A total of 3 healthy male volunteers (recruited in response to follow-up from flyers) with no prior medical history of heart conditions, diabetes or chronic skeletomuscular pain were recruited for participation in the study, and informed, signed consent was obtained from each individual following a rigorous prescreening procedure.”
    Quote in the paperNot a substantial claim

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

    Study design and conductnone given

    The study was deemed by the IRB as posing no greater than minimal risk to the prescreened subjects.

    “The study was deemed by the IRB as posing ‘no greater than minimal risk' to the prescreened subjects who were recruited for the investigation.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    The printed circuit board was assembled and tested in-vitro to validate both functionality and performance.

    “The printed circuit board was assembled and tested in-vitro to validate both functionality and performance.”
    Quote in the paperSubstantial claim

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

    Study design and conductnone given

    The ECG AFE was characterized using a CONTEC MS400 Multi-parameter Patient Simulator.

    “The electrocardiogram AFE was characterized using a CONTEC MS400 Multi-parameter Patient Simulator (electrocardiogram simulator).”
    Quote in the paperNot a substantial claim

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

    Study design and conductnone given

    All on-body experiments were performed in strict compliance with IRB guidelines and were approved by the Human Research Protections Program at University of California, San Diego (Project number 130,003).

    “All on-body experiments were performed in strict compliance with the guidelines of Institutional Review Boards (IRB) and were approved by the Human Research Protections Program at University of California, San Diego (Project name: Epidermal Electrochemical Sensors and Biosensors. Project number: 130,003).”
    Quote in the paperNot a substantial claim
14 of 14

  • The paper relies on this without support.

    The increasing cycling resistance protocol invokes anaerobic metabolism at similar time scales, augmenting lactate excretion in perspiration.

    “This ensured that the anaerobic metabolism was invoked at similar time scales, hence augmenting the excretion of lactate in the perspiration in a controlled manner.”

  • The paper relies on this without support.

    The epidermis and muscle tissues over the chest locations do not experience complex 3D strains and remain fairly stable even during intense physical activities.

    “In addition, the epidermis and muscle tissues over these locations do not experience complex 3D strains and remain fairly stable even during intense physical activities, making measurements here especially convenient.”

  • The paper relies on this without support.

    The performance of amperometric lactate electrodes is not compromised by reducing their dimension.

    “Since the performance of amperometric lactate electrodes is not compromised by reducing their dimension, they were fabricated between the two electrocardiogram electrodes, as shown in Fig. 1d.”

  • The paper relies on this without support.

    The commercial wristband heart rate monitor (BASIS) provides an accurate heart rate reference.

    “To validate electrocardiogram data over long time series, even under the presence of experimentally-induced motion, heart rate as extracted from the electrocardiogram data is benchmarked against a commercial wristband heat rate monitor (BASIS) for subjects 1 and 3.”

  • The paper relies on this without support.

    The commercially available 3M Red Dot ECG electrodes provide a valid reference for ECG morphology.

    “The ability of the printed electrocardiogram electrodes to record electrocardiogram signals was validated by comparing recordings from the fabricated electrodes with commercially-available 3M Red Dot electrocardiogram electrodes.”
5 of 5

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?

  • Polyurethane-based ion-selective membranes were integrated with textile-based potentiometric sensors to create stretchable diagnostic devices.

    “In another study, polyurethane‐based ion‐selective membranes were integrated with textile‐based potentiometric sensors to create stretchable diagnostic devices.35”

    From Wearables in Medicine (2018) · cites this paper as [35]

    The Methods section (“Printing and functionalization of Chem–Phys hybrid patch”; page unavailable) describes an amperometric lactate sensor and ECG electrodes printed on a flexible polyester substrate, not polyurethane-based ion-selective membranes integrated with textile potentiometric sensors. The Results section (“Hybrid patch design rationale and fabrication”; page unavailable) calls the device flexible, but does not describe it as the stretchable textile device claimed. (LLM, conf=0.88)

    Checked by a reasoning model — may be wrong.

    Experimental — accuracy not yet measured

  • Wearable sweat sensors address the limitation of traditional sweat testing by enabling in situ sweat measurements with real-time feedback, creating potential for preventive care, timely diagnosis, and treatment.

    “By taking advantage of flexible and hybrid electronics (13–17), wearable sweat sensors address this limitation by enabling in situ sweat measurements with real-time feedback, creating potential for preventive care, timely diagnosis, and treatment (18–34).”

    From Regional and correlative sweat analysis using high-throughput microfluidic sensing patches toward decoding sweat (2019) · cites this paper as [19]

    The Abstract says conventional clinical-lab and point-of-care testing cannot provide continuous, real-time measurements, and the Results (Epidermal evaluation; page unavailable) demonstrate continuous on-body sweat-lactate monitoring. The paper discusses monitoring and diagnostic opportunities, but does not specifically establish the claimed potential for preventive care, timely diagnosis, or treatment. (LLM, conf=0.83)

    Experimental — accuracy not yet measured

  • Na+ and K+ ion selective electrodes showed a limit of detection of ≈10−5 m.

    “Na+ and K+ ion selective electrodes showed a limit of detection of ≈10−5 m.35”

    From Wearables in Medicine (2018) · cites this paper as [35]

    The Results section on in-vitro characterization reports a detection range and sensitivity for a lactate biosensor, not detection limits for Na+ or K+ ion-selective electrodes. The Methods section on in-vitro studies likewise describes lactate and ECG sensors. Searches for Na+ and K+ electrodes and a 10−5 M detection limit found no passage addressing the claimed value; page numbers were unavailable. (LLM, conf=0.72)

    Experimental — accuracy not yet measured

  • Real-time monitoring showed that the ECG compared to current wearable devices was not affected by concurrent lactate detection.

    “Real-time monitoring showed that the ECG compared to current wearable devices was not affected by concurrent lactate detection.”

    From Wearable sensors for monitoring the physiological and biochemical profile of the athlete (2019) · cites this paper as [48]

  • Lactate levels measured by the biosensor closely approximated the expected sweat-lactate profile for increasing intensity workouts.

    “In addition, lactate levels measured by the biosensor closely approximated the expected sweat-lactate profile for increasing intensity workouts.”

    From Wearable sensors for monitoring the physiological and biochemical profile of the athlete (2019) · cites this paper as [48]

Cites

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Related

Authors
Imani, S., Bandodkar, A. J., Mohan, A. M. V., Kumar, R., Yu, S., Wang, J., & Mercier, P. P.
Affiliations
University of California San Diego (US)
Corresponding author
  • Wang, Joseph
  • Mercier, Patrick P.
ORCID
Venue
Nature Communications
Publisher
Springer Science and Business Media LLC
Published
2016-05-23
Volume
7
Issue
1
Pages
11650-11650
ISSN
2041-1723 (ISSN-L)
DOI
10.1038/ncomms11650
PMC
PMC4879240
OpenAlex
W2401823338
Semantic Scholar
ca05604884f0b3cf597f80f1d61b2fcdd0f4707f
Cited by
861
References
54
Citations by year
2026: 49 · 2025: 73 · 2024: 79 · 2023: 77 · 2022: 102 · 2021: 115 · 2020: 100 · 2019: 110 · 2018: 92 · 2017: 54 · 2016: 9
FWCI
42.52
Type
journal article
Language
en
Open access
Licence
Locations
  • Nature Communications (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • eScholarship (California Digital Library) (submittedVersion)
Funders
  • Arnold and Mabel Beckman Foundation
  • National Institutes of Health
  • Samsung
  • National Institute of Biomedical Imaging and Bioengineering (R21EB019698)
Topics
  • Physical Sciences › Engineering › Biomedical Engineering › Advanced Sensor and Energy Harvesting Materials
  • Physical Sciences › Engineering › Electrical and Electronic Engineering › Electrochemical sensors and biosensors
  • Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
Keywords
wearable biosensors, lactate biosensor, electrocardiogram, amperometric biosensor, flexible electronics, fitness tracking, health monitoring, biomarkers
MeSH terms
Electrocardiography, Exercise Test, Humans, Male, Monitoring, Physiologic, Sweat, Biosensing Techniques, Biomarkers, Lactic Acid

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