**Abstract**

The inchworm type piezoelectric actuator is one novel actuator to ensure a large working stroke with high resolution which has attracted the continuous attentions from researchers all over the world. In this study, the motion principle of the inchworm type piezoelectric is discussed: the "walker" pattern, the "pusher" pattern and hybrid "walker-pusher" pattern. The classification (linear, rotary and multi-DOF) and development are introduced in details, some significant researches are illustrated. Finally, the future direction of inchworm type piezoelectric actuators is pointed out according the development of inchworm type piezoelectric actuators. This study shows the clear principle, design and future of inchworm type piezoelectric actuators which is meaningful for the development of piezoelectric actuators.

**Keywords:** piezoelectric actuator, inchworm, large stroke, high resolution

## **1. Introduction**

Up to now, researchers have developed a variety of micro/Nano driving and positioning platforms based on piezoelectric materials. Among the developed piezoelectric platforms, many of them have been applied for biological cell manipulation, atomic manipulation, micro/nano indentation, aerial photography and other systems with great application results [1, 2]. However, the working stroke of piezoelectric components is quite small, often only a few micrometers or tens of micrometers, which seriously limits the further application of piezoelectric actuators. Therefore, many researchers have done a lot of work to overcome this shortcoming of piezoelectric components, so as to expand the application field of piezoelectric actuators [3]. The inchworm type piezoelectric actuator is one kind of the developed new piezoelectric actuators which is able to ensure a large working stroke and achieve nano-scale accuracy at the same time. It has a wide application demand in the fields which have strict requirements on output accuracy, space size and antielectronmagnetic interference. The study on inchworm piezoelectric actuators has become a hot spot in the application and research field of piezoelectric actuators in recent years [4, 5].
