Development of a Softness Sensing System by Using Dynamic Response of Piezoelectric Vibrator and Its Application to Detect Mechanical Properties of Living Cells.

Development of a reliable method to determine the "softness" of materials or objects will provide us some meaningful mechanical information. In this study, a novel method of sensing is specifically developed to detect softness of sponge-like soft and cell-like small objects by using dynamic response of piezoelectric vibrator. The bending mode of vibration of a small beam type vibrator is excited by using piezoelectric ceramics. Once the vibrating end of this vibrator is contacted on the soft object, the natural frequency of the vibrator could be changed according to degrees of its dynamic constraints at the end boundary. This frequency change has a certain kind of relationships with the mechanical properties of the object and is considered to give us useful indicator as the softness of that object. In order to demonstrate the capability of this sensing system, experimental studies have been carried out to detect softness of silicone rubber blocks and fertilized living egg cells of killifish.