A Low-Voltage Large-Displacement Large-Force Inchworm Actuator

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Inchworm microactuators are popular in micropositioning applications for their long ranges. However, until now, they could not be considered for applications such as <emphasis emphasistype="boldital">in vivo</emphasis> biomedical applications because of their high input voltages. This paper reports on the modeling, design, fabrication, and testing of a new family of pull-in-based electrostatic inchworm microactuators which provides a solution to this problem. Actuators with only 7-V operating voltage are achieved with a <formula formulatype="inline"><tex Notation="TeX">$\pm 18\hbox{-}\mu\hbox{m}$</tex></formula> total range and a <formula formulatype="inline"><tex Notation="TeX">$\pm 30\hbox{-}\mu\hbox{N}$</tex></formula> output force. Larger operating voltage (16 V) actuators show even better results in force (<formula formulatype="inline"><tex Notation="TeX">$\pm 110\ \mu \hbox{N}$</tex></formula>) and range <formula formulatype="inline"><tex Notation="TeX">$(\pm 35\ \mu\hbox{m})$</tex></formula>. The actuator has an in-plane angular deflection conversion which provides a force-displacement tradeoff and allows us to set step sizes varying from few nanometers to few micrometers with a minor change in design. In this paper, we designed 1- and 4-<formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> step-size devices. The actuator step size may change during the operation because of the slipping of the shuttle and the beam bending; however, our model successfully explains the reasons. One of our actuator prototypes has survived more than 25 million cycles without performance deterioration. The device is fabricated using the silicon-on-insulator-based multiuser MEMS process.<formula formulatype="inline"><tex Notation="TeX">$\hfill$</tex></formula>[2007-0146] </para>