Softness measurement by forceps-type tactile sensor using acoustic reflection

We have developed a forceps-type tactile sensor for palpation of a tumor in laparoscopic surgery. The sensor responds to contact position and force at deformable cavity in the sensor probe by using acoustic reflection. The sensor has high applicability for laparoscopic surgery because of its simple structure and disuse of electrical elements within inserted part into patient´s body. In this study, we try to measure softness of a contact tissue by using the sensor. Human can estimate softness from contact area and force. Indentation depth is not always required for softness perception. This perception mechanism suggests that our sensor has a possibility for softness measurement because the sensor can respond to contact position and force. Softness measurement contributes to tumor localization and improvement of diseases database. First, the sensor output characteristic is investigated for different soft samples. Then, a method of stiffness measurement using the sensor outputs is proposed. Experimental results show that the sensor has the capability of softness measurement without any additional sensors.