Ion‐Conductive Hydrogel‐Based Stretchable, Self‐Healing, and Transparent NO 2 Sensor with High Sensitivity and Selectivity at Room Temperature
Abstract
Here stretchable, self‐healable, and transparent gas sensors based on salt‐infiltrated hydrogels for high‐performance NO 2 sensing in both anaerobic environment and air at room temperature, are reported. The salt‐infiltrated hydrogel displays high sensitivity to NO 2 (119.9%/ppm), short response and recovery time (29.8 and 41.0 s, respectively), good linearity, low theoretical limit of detection (LOD) of 86 ppt, high selectivity, stability, and conductivity. A new gas sensing mechanism based on redox reactions occurring at the electrode–hydrogel interface is proposed to understand the sensing behaviors. The gas sensing performance of hydrogel is greatly improved by incorporating calcium chloride (CaCl 2 ) in the hydrogel via a facile salt‐infiltration strategy, leading to a higher sensitivity (2.32 times) and much lower LOD (0.06 times). Notably, both the gas sensing ability, conductivity, and mechanical deformability of hydrogels are readily self‐healable after cutting off and reconnection. Such large deformations as 100% strain do not deprive the gas sensing capability, but rather shorten the response and recovery time significantly. The CaCl 2 ‐infiltrated hydrogel shows excellent selectivity of NO 2 , with good immunity to the interference gases. These results indicate that the salt‐infiltrated hydrogel has great potential for wearable electronics equipped with gas sensing capability in both anaerobic and aerobic environments.
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Addition of CaCl2 to PAM/Carr DN hydrogels enhanced conductivity, inhibited dissolution of NH3 and other gases, and improved NO2 selectivity of the hydrogel.
“The addition of CaCl2 enhanced the conductivity, inhibited the dissolution of NH3 and other gases, and improved the NO2 selectivity of the hydrogel”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
Addition of CaCl2 promoted the redox NO2 reaction in the hydrogel and electrode, enhancing the response characteristics of the hydrogel.
“it promoted the redox NO2 reaction in the hydrogel and electrode, which enhanced the response characteristics of the hydrogel”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
The sensitive characteristics of the sensor are not affected by tensile deformation, and it can maintain the sensing of NO2 even at 100% strain with shortened response and recovery time.
“Moreover, the sensitive characteristics of the sensor are not affected by tensile deformation, and it can maintain the sensing of NO2 even at 100% strain with shortened response and recovery time.”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
In the presence of CaCl2, the PAM/Carr DN hydrogel NO2 sensor exhibited a high sensitivity of 119.9%, short response and recovery time (29.8 and 41.0 s, respectively), good linearity, low theoretical LOD of 86 ppt, high selectivity, stability, and ionic conductivity.
“In the presence of CaCl2, this hydrogel NO2 sensor exhibited a high sensitivity of 119.9%, short response and recovery time (29.8 and 41.0 s, respectively), good linearity, low theoretical limit of detection (LOD) of 86 ppt, high selectivity, stability, and ionic conductivity.”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
Under the same temperature and humidity, the NO2 response of the sensor with five turns of the Ag electrode was significantly greater than that with one turn.
“Under the same temperature and humidity, the NO2 response of the sensor with five turns of the Ag electrode was significantly greater than that with one turn, as depicted in Fig. 6f.”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
Wu et al. [150] developed a salt infiltrated hydrogel that can realize real-time monitoring of NO2 at room temperature without any other treatments.
“Wu et al. [150] developed a salt infiltrated hydrogel that can realize real-time monitoring of NO2 at room temperature without any other treatments.”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
The sensor is self-healing as it recovers after being truncated and does not affect the conductive and sensitive properties.
“The sensor is self-healing as it recovers after being truncated and does not affect the conductive and sensitive properties, which means it is more tolerant, as shown in Fig. 8c.”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
SEM observation after the response reaction showed an additional layer of AgCl on the anode electrode, supporting the proposed deduction.
“Figure 6c shows an additional layer of AgCl added to the anode electrode, which reflects the reliability of the previous deduction from the side.”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
In electrode-masking experiments, if the anode is covered, the sensor continuously responds, whereas if the cathode is covered, the sensor does not produce sensing signals for NO2.
“If the anode is covered, the sensor continuously responds, whereas if the cathode is covered, the sensor does not produce sensing signals for NO2.”
From Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors. (2023) · cites this paper as [150]
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Functionalized Hydrogel-Based Wearable Gas and Humidity Sensors.
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Self-citationHumidity Sensing of Stretchable and Transparent Hydrogel Films for Wireless Respiration Monitoring
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- Authors
- Wu, Z., Rong, L., Yang, J., Wei, Y., Tao, K., Zhou, Y., Yang, B., Xie, X., & Wu, J.
- Affiliations
- Sun Yat-sen University (CN)
- Northwestern Polytechnical University (CN)
- Guangdong Medical College (CN)
- Corresponding author
- Wu, Jin
- Venue
- Small
- Publisher
- Wiley
- Published
- 2021-10-20
- Volume
- 17
- Issue
- 52
- Pages
- e2104997-e2104997
- ISSN
- 1613-6810 (ISSN-L)
- 1613-6829
- OpenAlex
- W3207077743
- Cited by
- 97
- References
- 4
- Citations by year
- 2026: 11 · 2025: 20 · 2024: 18 · 2023: 19 · 2022: 27 · 2021: 2
- FWCI
- 4.85
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Small (publishedVersion)
- PubMed (publishedVersion)
- Funders
- National Natural Science Foundation of China (61801525)
- Fundamental Research Funds for the Central Universities (2021qntd09)
- Natural Science Foundation of Guangdong Province (2018A030313400)
- Topics
- Physical Sciences › Engineering › Electrical and Electronic Engineering › Gas Sensing Nanomaterials and Sensors
- Physical Sciences › Engineering › Biomedical Engineering › Advanced Sensor and Energy Harvesting Materials
- Physical Sciences › Materials Science › Polymers and Plastics › Conducting polymers and applications
- Keywords
- NO2 gas sensor, self-healing hydrogels, salt infiltration, calcium chloride, wearable electronics, room-temperature gas sensing
- MeSH terms
- Wearable Electronic Devices, Electric Conductivity, Nitrogen Dioxide, Temperature, Hydrogels
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