Ultra-thin Hydrogel E-skin with High Resolution for Thermal and Tactile Haptics

Electronic skin (e-skin) that can perceive thermal and tactile stimuli with high resolution enables intelligent robots a realistic haptic sensation. These e-skins usually achieve spatial perception through an array arrangement of multiple sensors. However, the resolution of most e-skins is limited to centimeter level due to the structural complexity and manufacturing difficulty. Herein, we proposed a hydrogel e-skin that realizes high-resolution spatial mapping of temperature and pressure by constructing an electrode array-thermogalvanic hydrogel-electrode array sandwich structure. This hydrogel e-skin achieves temperature and pressure dual sensing through the thermogalvanic and piezoresistive effect of the redox couple in the horizontal and vertical direction, respectively. A reference electrode for temperature sensing is introduced in the horizontal direction so that the temperature shift of the bottom electrode under external thermal stimuli will no longer affect the accuracy of thermal perception. The reduction in hydrogel thickness effectively eliminates crosstalk between pixels and achieves millimeter-level spatial resolution of both temperature and pressure. The dexterous robot hand covered by our hydrogel e-skin shows the ability of distinguishing the contact object by perceiving the external temperature and pressure distribution. Our work provides a new strategy for multifunctional e-skin with high resolution and may promote the development of human-machine interaction.