Flexible membrane tactile sensor for contact traction distribution measurement on a microscale

A novel thin film polydimethylsiloxane (PDMS) based flexible tactile micro sensor has been developed for contact traction distribution measurement between an indenter and an object (e.g. finger pad). The tactile sensor is a five layer device consisting of 2 layers of textured patterns sandwiched between 3 layers of PDMS. The textured patterns are protected by a thin layer of PDMS (25 microns) on each side and are separated by a thicker PDMS layer (100 microns). The sensor thus has a total thickness of 150 microns, much less than the thickness of the human fingertip skin. The entire device is fabricated bottom up on a silicon wafer using soft lithography and microfabrication techniques. The sensor is designed to be used with an imaging apparatus (in our case we use an Optical Coherence Tomography (OCT) apparatus). The deflection of the patterns due to an applied load is imaged by the OCT and is used to estimate the stress at the sensor and object interface by solving the stress inverse problem analytically. Results are presented to illustrate the use of the microsensor to estimate the contact traction distribution due to a spherical indenter of radius 500 μm.