Pressure sensing is an important function of electronic skin devices. The development of pressure sensors that can mimic and surpass the subtle pressure sensing properties of natural skin requires the rational design of materials and devices. Here we present an ultrasensitive resistive pressure sensor based on an elastic, microstructured conducting polymer thin film. The elastic microstructured film is prepared from a polypyrrole hydrogel using a multiphase reaction that produced a hollow-sphere microstructure that endows polypyrrole with structure-derived elasticity and a low effective elastic modulus. The contact area between the microstructured thin film and the electrodes increases with the application of pressure, enabling the device to detect low pressures with ultra-high sensitivity. Our pressure sensor based on an elastic microstructured thin film enables the detection of pressures of less than 1 Pa and exhibits a short response time, good reproducibility, excellent cycling stability and temperature-stable sensing.

Conducting polymer hydrogels represent a unique class of materials that synergizes the advantageous features of hydrogels and organic conductors and have been used in many applications such as bioelectronics and energy storage devices. They are often synthesized by polymerizing conductive polymer monomer within a nonconducting hydrogel matrix, resulting in deterioration of their electrical properties. Here, we report a scalable and versatile synthesis of multifunctional polyaniline (PAni) hydrogel with excellent electronic conductivity and electrochemical properties. With high surface area and three-dimensional porous nanostructures, the PAni hydrogels demonstrated potential as high-performance supercapacitor electrodes with high specific capacitance (∼480 F·g −1 ), unprecedented rate capability, and cycling stability (∼83% capacitance retention after 10,000 cycles). The PAni hydrogels can also function as the active component of glucose oxidase sensors with fast response time (∼0.3 s) and superior sensitivity (∼16.7 μA·mM −1 ). The scalable synthesis and excellent electrode performance of the PAni hydrogel make it an attractive candidate for bioelectronics and future-generation energy storage electrodes.conductive polymer hydrogel | supercapacitors | biosensors H ydrogels are polymeric networks that have a high level of hydration and three-dimensional (3D) microstructures bearing similarities to natural tissues (1, 2). Hydrogels based on conducting polymers [e.g., polythiophene, polyaniline (PAni), and polypyrrole] combine the unique properties of hydrogels with the electrical and optical properties of metals or semiconductors (3-6) thus offering an array of features such as intrinsic 3D microstructured conducting frameworks that promote the transport of charges, ions, and molecules (7). Conducting polymer hydrogels provide an excellent interface between the electronictransporting phase (electrode) and the ionic-transporting phase (electrolyte), between biological and synthetic systems, as well as between soft and hard materials (8). As a result, conducting polymer hydrogels have demonstrated great potential for a broad range of applications from energy storage devices such as biofuel cells and supercapacitors, to molecular and bioelectronics (9) and medical electrodes (8).To date, the synthetic routes toward conducting polymer hydrogels include synthesizing a conducting polymer monomer within a nonconducting hydrogel matrix (8, 9) using multivalent metal ions (Fe 3þ or Mg 2þ ) to crosslink poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) (10, 11) and using nonconducting poly(ethylene glycol) diglycidyl ether, or poly(styrenesulfonate) to crosslink PAni (12, 13); however, nonconducting hydrogel matrix and polymers result in the deterioration of the electrical properties, whereas excessive metal ions may reduce the biocompatibility of hydrogels. Moreover, there have yet been any reports in regard to conductive hydrogels that can be facilely micropatterned, which is important for fabricating hy...