Development of a flexible tactile sensor using area-arrayed bundle structures of multi-walled carbon nanotubes

In recent years, surgical assisting robots and nursing care robots are being introduced to medical and nursing fields due to the rapid increase of the aging society. In order to assure the safety and reliability of these robots, a highly sensitive tactile sensor is necessary to detect the state of contact between these robots and human body. The target specifications of this sensor are spatial resolution of less than 1 mm, and the pressure sensitivity of less than 10 kPa. Since the tactile sensor is expected to be attached on the tip of a surgical assisting robot or the arm of a nursing care robot, it should be small and flexible and highly sensitive to contact pressure. In this study, high quality MWCNT (Multi-Wall Carbon Nanotube) has been synthesized to develop two types of tactile sensors which consisted of a MWCNT film and the area-arrayed MWCNT bundles. Thermal CVD (Chemical Vapor Deposition) method was applied to the growth of MWCNT and PDMS (Polydimethylsiloxane) was used for a flexible substrate. It was found that MWCNT bundles showed elastic deformation in the compressive strain range from 0% to 60%. The PDMS substrate showed elastic deformation under the application of bending strain of about 20%. In addition, it was confirmed that the detecting resolution of the force was lower than 1 mN, and the obtained gauge factor of the developed sensor was about 3.5.