Microstructured Ionic Polymer-Based Multifunctional Iontronic Skin for Pressure Sensing, Object Recognition, and...

Skin-like iontronic sensors capable of multifunctional sensing and reliable operation hold strong potential for next-generation wearable electronics, human-machine interfaces, and underwater technologies. However, simultaneously achieving high sensitivity and multifunctionality within a single platform remains a significant challenge. Here, we report a multifunctional iontronic skin based on a microstructured ionic polymer (MSiP) composed of PVDF and [EMIM]+[BF4]- ion pairs. The MSiP is fabricated through mask-less photolithography to create highly ordered micropillar arrays with a diameter of 30 μm, a height of 5 μm, and an interspacing of 20 μm. The iontronic skin is constructed by sandwiching the MSiP layer between flexible PDMS/PEDOT:PSS electrodes, where pressure-induced migration of highly mobile [BF4]- ions, as revealed by molecular dynamics simulations, facilitates electrical double-layer formation at the MSiP/electrode interface, resulting in enhanced capacitive response. Moreover, finite-element simulations reveal that the microstructured architecture effectively concentrates local stress, increases the effective contact area, and amplifies structural deformation during compression, thereby accounting for the exceptional pressure sensitivity of the MSiP sensor. As a result, the sensor achieves an ultrahigh pressure sensitivity of 833 kPa-1, a highly linear response (R2 = 0.98), and excellent durability over 20,000 loading-unloading cycles. Its remarkable sensitivity enables the detection of pressures as low as 3 Pa. Furthermore, integration with a robotic arm enables the development of a tactile robotic interface platform capable of real-time object grasping, lifting, and releasing in response to tactile forces applied to the sensor surface. The sensor can also be attached to the human body to monitor physiological signals and various body movements. Beyond tactile sensing, when combined with machine learning, the sensor can accurately distinguish objects ranging from soft cloth to rigid steel bottles, achieving a high classification accuracy of 95-97%. The iontronic sensor also demonstrates underwater sensing, including monitoring of depth (0-35 cm), temperature (20-80 °C), and salinity (0-8 ppt). This work presents a versatile iontronic platform that enables high-performance multifunctional sensing for wearable electronics, intelligent robotics, human-machine interfaces, and underwater environmental monitoring.