Touch sensor for micromanipulation with pipette using lead-free (K,Na)(Nb,Ta)O3 piezoelectric ceramics

Abstract

In the field of applied microbiology, a touch sensor for micromanipulation with a pipette is needed. Therefore, we previously developed a touch sensor using Pb(Zr,Ti)O3 (PZT). The piezoelectric material is used for vibration of the pipette and for measurement of the change in mechanical impedance caused by the pipette tip contacting the object being measured. However, the lead included in PZT can cause environmental problems. Therefore, in the present work, we developed a touch sensor using lead-free (K,Na)(Nb,Ta)O3 (KNNT) ceramics, which are strong candidates for lead-free piezoelectric ceramics. In this study, characteristics of a touch sensor utilizing piezoelectric vibration were theoretically derived. The results show that the piezoelectric constant d31 is very important: the higher the mode of vibration, the smaller the tip amplitude; the lower the mode of vibration, the higher the sensitivity. Also, the higher the elasticity or viscosity of the object in contact with the sensor, the higher the sensitivity. These theoretical results qualitatively correspond to the experimental results. The piezoelectric constant d31 of KNNT ceramics was measured, and its value was found to be greater than or equal to 100pm∕V. KNNT ceramics were applied to the touch sensor and its utility was confirmed.