Soft Wearable Tactile Sensor for Softness Evaluation through Internal Examination

In obstetrics and gynecology, internal examination, i.e., palpation of the cervix, is performed to diagnose the risk of miscarriage and preterm birth based on its hardness. However, the diagnosis is subjective and requires high skill. The introduction of technologies for quantifying cervical stiffness can increase the accuracy of the diagnosis. Various softness sensors have been proposed, but because the route to the cervix is curved and narrow, they are not suitable for the internal examination. Safety for pregnant women and fetuses must be also taken into consideration. In this paper, we propose a soft wearable tactile sensor made entirely of silicone rubber. The structure is simple and the sensing principle is based on acoustic reflection, which is safe because no electricity flows inside the body and its texture is soft. Furthermore, the sensor is worn at the clinician’s fingertip thus allowing him/her to make use of his/her skill. The sensor measures contact forces at three points of the fingertip considering human’s softness perception. Experimental results showed that the fabricated sensor is capable of determining two magnitudes of hardness (Young’s modulus 120 kPa and 230 kPa) within a fingertip orientation from 30° to 60°.