ABSTRACT
Flexible pressure sensors developed rapidly with increased sensitivity, a fast response time, high stability, and excellent deformability. These progresses have expanded the application of wearable electronics under high-pressure backgrounds while also bringing new challenges. In particular, the nonlinearity and narrow working range lead to a gradually insensitive response, principally because the microstructure deforms inconsistently on the device interfaces in the whole working range. Herein, we report an ionic flexible sensor with a record-high linearity (R2 = 0.99994) in a wide working range (up to 600 kPa). The linearity response comes from the normal-direction graded hemisphere (GH) microstructure. It is prepared from poly(dimethylsiloxane) (PDMS)/carbon nanotubes (CNTs)/Au into flexible and deformable electrodes, and its geometry is precisely designed from the linear elastic theory and optimized through finite element simulation. The sensor can achieve a high sensitivity of S = 165.5 kPa-1, a response-relaxation time of <30 ms, and superb consistency, allowing the device to detect vibration signals. Our sensor has been assembled with circuits and capsulation in order to monitor the function state of players in underwater sports in the frequency domain. This work deepens the theory of linearized design of microstructures and provides a strategy to make flexible pressure sensors that have combined the performances of ultrahigh linearity, high sensitivity, and a wide working range.
ABSTRACT
Underwater flexible sensors have a future for wide application, which is promising for attaching them to underwater creatures to monitor vital signals and biomechanical analysis of their motion and perceive tiny environmental disturbances. However, the pressure waves induced by biological swimming are extremely weak and susceptible to undercurrents, making them difficult to sense. Here, we report an ultrahighly sensitive biomimetic electronic fish skin designed by embedding an artificial pseudocapacitive-based hair cell into a simulated canal neuromast encapsulation structure, in which the artificial hair cell, as the key sensitive unit, is assembled from hybrid film electrodes and polyurethane-acidic electrolyte foam. Such a film is prepared by inter-cross-linking MXene and holey reduced graphene oxide with the assistance of l-cysteine, effectively increasing the interfacial capacitance and alleviating the oxidation issues of MXene. Meanwhile, the acidic foam with high porosity shows great compressibility to adapt to a high-pressure underwater environment. Consequently, the device exhibits ultrahighly sensitivity (maximum sensitivity â¼173688 kPa-1) over a wide range of depths (0-100 m) and remains stable after 10000 repeated tests. As an example case, the device is integrated as a motion monitoring system to identify the minor disturbances triggered by instantaneous postural changes of fish. The electronic fish skin is expected to demonstrate enormous potentials in flow field monitoring, ocean current detecting, and even seismic waves warning.
