The large expansion of the robotic field in the last decades has created a growing interest in the research and development of tactile sensing solutions for robot hand and body integration. Piezoresistive composites are one of the most widely employed materials for this purpose, combining simple and low cost preparation with high flexibility and conformability to surfaces, low power consumption, and the use of simple read-out electronics. This work provides a review on the different type of composite materials, classified according to the conduction mechanism and analyzing the physics behind it. In particular piezoresistors, strain gauges, percolative and quantum tunnelling devices are reviewed here, with a perspective overview on the most used filler types and polymeric matrices. A description of the state-of-the-art of the tactile sensor solutions from the point of view of the architecture, the design and the performance is also reviewed, with a perspective outlook on the main promising applications.

New photo-curable polymers suitable for 3D printing are here provided, exhibiting a mechanical light-responsivity upon laser irradiation. Azobenzene moieties are employed both as a dye component in the 3DP and as active groups, providing photo-mechanical responsivity. The incorporation of azobenzene units into polymeric matrices allows a reversible and controllable change of the Young's modulus of 3D printed micrometric structures.

Self‐healing ionic conductive hydrogels have shown significant potential in applications like wearable electronics, soft robotics, and prosthetics because of their high strain sensitivity and mechanical and electrical recovery after damage. Despite the enormous interest in these materials, conventional fabrication techniques hamper their use in advanced devices since only limited geometries can be obtained, preventing proper conformability to the complexity of human or robotic bodies. Here, a photocurable hydrogel with excellent sensitivity to mechanical deformations based on a semi‐interpenetrating polymeric network is reported, which holds remarkable mechanical properties (ultimate tensile strain of 550%) and spontaneous self‐healing capabilities, with complete recovery of its strain sensitivity after damages. Furthermore, the developed material can be processed by digital light processing 3D printing technology to fabricate complex‐shaped strain sensors, increasing mechanical stress sensitivity with respect to simple sensor geometries, reaching an exceptional pressure detection limit below 1 Pa. Additionally, the hydrogel is used as an electrolyte in the fabrication of a laser‐induced graphene‐based supercapacitor, then incorporated into a 3D‐printed sensor to create a self‐powered, fully integrated device. These findings demonstrate that by using 3D printing, it is possible to produce multifunctional, self‐powered sensors, appropriately shaped depending on the various applications, without the use of bulky batteries.