Flexible Proximity-Triaxial Force Micro Sensor: Design, Modelling and Simulation

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. The localization of the object to be grasped is a fundamental requirement, before it is possible to start the grasp. During this task, it is necessary to track the object in the robotic hands working range, by means of proximity sensors, to establish controlled contacts. Concerning this point, ultrasonic transducers are nowadays largely adopted in range finding applications, replacing the use of integrated cameras. 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. 

Figure 1: a) Conceptual sketch of a piezoresistive triaxial tactile sensor; b) Lateral view of the performing deformation mode due to the normal force and the shear force (right) [Nakashima et al. 2022]. 

The goal of the present master thesis proposal is the design, modelling and simulation of an all-in-one MEMS flexible proximity-triaxial force sensor. This project will give an opportunity to perform a mechanical and electrical analysis of a MEMS system, as well as to participate in development of the state-of-the art proximity-tactile sensors. Generally, this is a topic for students eager to understand complex systems with a hands-on attitude and interest for MEMS devices and multiphysics simulations. High creativity is much appreciated. The work is estimated to be: 50% design, 50% modelling and simulations/calculations (e.g.  COMSOL, Matlab or likewise).