Wearable dry electrodes are needed for long-term biopotential recordings but are limited by their imperfect compliance with the skin, especially during body movements and sweat secretions, resulting in high interfacial impedance and motion artifacts. Herein, we report an intrinsically conductive polymer dry electrode with excellent self-adhesiveness, stretchability, and conductivity. It shows much lower skin-contact impedance and noise in static and dynamic measurement than the current dry electrodes and standard gel electrodes, enabling to acquire high-quality electrocardiogram (ECG), electromyogram (EMG) and electroencephalogram (EEG) signals in various conditions such as dry and wet skin and during body movement. Hence, this dry electrode can be used for long-term healthcare monitoring in complex daily conditions. We further investigated the capabilities of this electrode in a clinical setting and realized its ability to detect the arrhythmia features of atrial fibrillation accurately, and quantify muscle activity during deep tendon reflex testing and contraction against resistance.

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Stretchable electronic materials and devices have important applications in flexible electronic systems including wearable electronics and bioelectronics. Convenient electricity generation such as thermoelectric conversion is required for the flexible electronic systems. Hence, it is development of high‐performance thermoelectric materials with high mechanical stretchability would be highly desirable. Here, stretchable and transparent ionogels with high thermoelectric properties are demonstrated. The ionogels made of elastomeric waterborne polyurethane and 1‐ethyl‐3‐methylimidazolium dicyanamide (EMIM:DCA, an ionic liquid) are prepared by solution processing. Their mechanical and electrical properties depend on the loading of EMIM:DCA. The ionogels with 40 wt% EMIM:DCA can have a high mechanical stretchability of up to 156%, low tensile strength of 0.6 MPa, and low Young's modulus of 0.6 MPa. They also exhibit a high ionic thermovoltage of 34.5 mV K−1, high ionic conductivity of 8.4 mS cm−1 and low thermal conductivity of 0.23 W m−1 K−1 at a relative humidity of 90%. As a result, it can have a high ionic figure of merit (ZTi) of 1.3 ± 0.2. Both the thermovoltage and the ZTi value are the highest for stretchable thermoelectric materials. They can be used in ionic thermoelectric capacitors to convert heat into electricity.

Wearable stretchable strain sensors can have important applications in many areas. However, the high noise is a big hurdle for their application to monitor body movement. The noise is mainly due to the motion artifacts related to the poor contact between the sensors and skin. Here, wearable stretchable dry and self‐adhesive strain sensors that can always form conformal contact to skin even during body movement are demonstrated. They are prepared via solution coating and consist of two layers, a dry adhesive layer made of biocompatible elastomeric waterborne polyurethane and a sensing layer made of a non‐adhesive composite of reduced graphene oxide and carbon nanotubes. The adhesive layer makes the sensors conformal to skin, while the sensing layer exhibits a resistance sensitive to strain. The sensors are used to accurately monitor both small‐ and large‐scale body movements, including various joint movements and muscle movements. They can always generate high‐quality signals even on curvilinear skin surface and during irregular skin deformation. The sensitivity is remarkably higher while the noise is saliently lower than the non‐adhesive strain sensors. They can also be used to monitor the movements along two perpendicular directions, which cannot be achieved by the non‐adhesive strain sensors.

Stretchable electronic materials have drawn strong interest due to their important applications in areas such as bioelectronics, wearable devices, and soft robotics. The stretchable electrode is an integral unit of stretchable systems. Intrinsically c o n d u c t i v e p o l y m e r s s u c h a s p o l y ( 3 , 4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) can have high mechanical flexibility and good biocompatibility. However, their electrical conductivity and mechanical stretchability should be greatly improved for its applications as the stretchable electrode. Here, we report highly conductive and highly stretchable PEDOT:PSS by incorporating biocompatible D-sorbitol. D-Sorbitol can serve as both the secondary dopant and plasticizer for PEDOT:PSS. It can not only significantly improve the conductivity but also the stretchability. D-Sorbitol-PEDOT:PSS (s-PEDOT:PSS) can have a conductivity of >1000 S/cm, and the conductivity could be maintained at a strain up to 60%. The resistance of s-PEDOT:PSS remains almost constant during repeated stretching−releasing cycles. The mechanism for the stretchability improvement by D-sorbitol is ascribed to the softening of PSSH chains. D-Sorbitol can position among the PSSH chains and thus destructs the hydrogen bonds among the PSSH chains. This makes the conformational change of the PSSH chains under stress become easy and thus increases the mechanical flexibility of PEDOT:PSS. This conductivity is the highest for biocompatible intrinsically conductive polymers with high stretchability.