ABSTRACT
Electrophysiology, exploring vital electrical phenomena in living organisms, anticipates broader integration into daily life through wearable devices and epidermal electrodes. However, addressing the challenges of the electrode durability and motion artifacts is essential to enable continuous and long-term biopotential signal monitoring, presenting a hurdle for its seamless implementation in daily life. To address these challenges, an ultrathin polymeric conductive adhesive, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)/polyvinyl alcohol/d-sorbitol (PPd) electrode with enhanced adhesion, stretchability, and skin conformability, is presented. The skin conformability and stability of electrodes is designed by theoretical criteria obtained by mechanical analysis. Thus, impedance stability is obtained over 1-week of daily life, and the PPd electrode addresses the challenges related to durability during prolonged usage. Proving stability in electromyography (EMG) signals during high-intensity exercise, the wireless PPd measurement system exhibits high signal-to-noise ratio (SNR) signals even in situations involving significant and repetitive skin deformation. Throughout continuous 1 week-long electrocardiogram (ECG) monitoring in daily life, the system consistently preserves signal quality, underscoring the heightened durability and applicability of the PPd measurement system.
Subject(s)
Adhesives , Electric Conductivity , Electrodes , Adhesives/chemistry , Humans , Wearable Electronic Devices , Polystyrenes/chemistry , Polymers/chemistry , Epidermis/physiology , Electromyography/methods , Polyvinyl Alcohol/chemistry , Electrocardiography , Signal-To-Noise Ratio , Bridged Bicyclo Compounds, Heterocyclic/chemistry , Monitoring, Physiologic/instrumentation , Monitoring, Physiologic/methods , Thiophenes/chemistryABSTRACT
Among many flexible mechanosensors, a crack-based sensor inspired by a spider's slit organ has received considerable attention due to its great sensitivity compared to previous strain sensors. The sensor's limitation, however, lies on its vulnerability to stress concentration and the metal layers' delamination. To address this issue of vulnerability, we used fluorinated ethylene propylene (FEP) as an encapsulation layer on both sides of the sensor. The excellent waterproof and chemical resistance capability of FEP may effectively protect the sensor from damage in water and chemicals while improving the durability against friction.
ABSTRACT
Although sensitivity and durability are desirable in a sensor, both of them cannot be easily achieved. Site-specific and effective signal acquisition on the limited area of a sensor inevitably allows fatigue accumulation and contamination. For example, an ultrasensitive nanoscale-crack-based sensor for detecting a mechanical stimulus with tremendous sensitivity (a gauge factor greater than 2000 under 2% strain), yet limited durability (up to a few thousand stretching cycles in tensile tests) has been presented previously. Herein, we suggest a simple yet robust nanoscale-crack-based sensor that achieves remarkable durability through the use of a self-healable polymer. The self-healable polymer helps the crack gap recover and maintain high stability for 1 million cycles under 2% strain. Moreover, site-specific recovery with infrared light irradiation was demonstrated with monolithic arrayed sensors. The proposed strategy provides a unique solution to achieving highly enhanced durability and high mechanosensitivity, which are typically incompatible.