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 o r objects will provide us some meaningful mechanical information. In this s tudy, a novel method of sensing is specifically developed to detect softnes s 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 t ype vibrator is excited by using piezoelectric ceramics. Once the vibrating end of this vibrator is contacted on the soft object, the natural frequenc y of the vibrator could be changed according to degrees of its dynamic cons traints at the end boundary. This frequency change has a certain kind of re lationships with the mechanical properties of the object and is considered to give us useful indicator as the softness of that object. In order to dem onstrate the capability of this sensing system, experimental studies have b een carried out to detect softness of silicone rubber blocks and fertilized living egg cells of killifish.