Flexible Triaxial Force Micro Sensor: Characterization

​The fourth industrial revolution, driven by smart automation technologies, internet of things, big data, artificial intelligence and advanced robotics blurs the lines between the physical and digital worlds. Fundamental changes took place in the supply network and in several environments where automated machines operate. The level of cooperation among robots and the interaction between robots and humans is continuously increasing.

Grasping objects is still a challenging task for service robots. In this context, triaxial force sensors provide the required tactile feedback to dexterously manipulate objects. During the functioning the involved movement usually induces large strains generation. Indeed, high flexibility is required for the employed sensors. Finally, size is a critical factor in robotic applications such as high precision manufacturing and surgery. MEMS technology provides required dimensions, extremely accurate and reliable fabrication processes. Therefore, it represents an ideal candidate to solve some of the crucial problems in this field.

Tactile sensors presented in literature are based on different performing principles. As a matter of fact, piezoresistive, piezoelectric and capacitive devices are adopted. In figure 1, a conceptual sketch of a piezoresistive triaxial force sensor is reported. It consists of 4 laser-induced graphene (LIG) cantilevers, inserted into an elastic protective body, on a flexible substrate made of Polyimide. The cantilevers deform under the normal and shear forces, consequently the mechanical strains induce an observed change of electrical resistance.