To smoothly drive an electron micro

To smoothly drive an electron microscopesampling container, we designed a novel stage that includesa piezoelectric actuator to achieve an automatic feedingsystem for microfluidic sampling processes, utilizing cap-illary action. The capacitive sensor measures the capaci-tance value that is used to identify the distance between thesample container and microfluidic samples; according tothis value, the microcontroller adjusts the velocity of thepiezoelectric actuator through pulse-width modulation andthe microstepping motion is realized. We developed theautomatic feeding system from this concept by using alinear piezoelectric actuator, a driving circuit, and a posi-tion-sensing integrated circuit. When the driving signal wasat 100% duty ratio, the velocity of the sampling containerachieved to 72 mm/s. To slowly approach liquid sample,driving the actuator at 5% duty cycle, the microsteppingresolution was 1 lm. Moreover, a driving circuit for thepiezoelectric actuator involving a phase-locked loop wasdeveloped to automatically track the resonance frequencyof the piezoelectric actuator.