The fast development of wearable sensors has been promoted by the broad needs for real-time monitoring the bodily functions and air quality. Interests in many wearables electronic sensors however have seen a decrease over time, due to the needs of frequent charging of batteries in practical usage. Wearable colorimetric sensors, using optical read-out signals under ambient light without any electronic components, become highly advantageous. Here we report an adaptive colorimetric sensing platform based on a bulk structure of covalently bonded hydrogel thin film-substrate system. External stimuli from the analytes can rapidly change the thickness of the hydrogel film, resulting in an instant color change. The soft and highly stretchable robust synthetic hydrogel materials can form a highly compliant contact to human epidermis and has good self-recovery capability, as an ideal candidate for soft matrices of wearable devices. Also, this colorimetric sensing platform allows for in situ quantitative analysis by naked eye or camera via analysis app, as a wireless wearable sensing component for the next-generation textile. We have shown this customizable adaptive platform can detect a large variety of analytes including cations for hydration and other physiologic metabolic state monitoring, Cu<sup>2+</sup> for Wilson's disease prescreening, glucose for diabetes monitoring, and sulfur dioxide and nitrogen dioxide for air quality detecting. This sensing platform showed a high performance on the sensitivity and response time. The limit of detection for Cu<sup>2+</sup> could reach as low as 10.0 pM with only 1-2 second. Such high performance is attributed by this unique chemo-mechano-optical signal transduction mechanism, which effectively amplifies the nm-scale hydrogel thickness change to a greater and more detectable optical spectrum change. This will lead to a broad platform of a new class of wearable sensors with superior performance at low cost.

Ultra-sensitive, highly-selective, real-time chemical wearable sensors based on hydrogel interferometer

256th National Meeting (2018)

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