Elasticity sensor using different tactile properties on one chip

We report a MEMS-based force sensor that can measure the elasticity of an object without information of contact force and object deformation. In our sensor, a polydimethylsiloxane (PDMS) pad is attached to a sensor chip that has three piezoresistive strain sensors as shown in Fig. 1(a). The PDMS pad has free ends whose deformations become larger as the object becomes softer in comparison with the deformation of the pad's center. By locating the strain sensors at these locations, it is possible to measure the elasticity of the object from the ratio of the sensors' outputs. We demonstrate by experiment results that the prototype sensor in this study can measure elasticity in a range of 50 kPa to 6 MPa. With the advantages of miniaturized size, simple sensing scheme, the proposed sensor is expected to be useful in robot manipulation and minimal invasive surgery (MIS).