Piezoelectric Grippers for Mobile Micromanipulation

The ability to efficiently and precisely manipulate objects in inaccessible environments is becoming an essential requirement for many applications of mobile robots, particularly at small sizes. Here, we propose and implement a mobile micromanipulation solution using a piezoelectric microgripper integrated into a dexterous robot, HAMR (the Harvard Ambulatory MicroRobot), that has a size of approximately 4.5 cm by 4 cm by 2.3 cm and a maximum payload of approximately 3 g. Our 100 mg miniature gripper is composed of recurve piezoelectric actuators that produce parallel jaw motions (stroke of 236 $\pm$ 32 $\mu$m at 200 V) while providing high gripping forces (blocked force of 0.575 N at 200 V), making it effective for micromanipulation applications with tiny objects. Using this gripper, we successfully demonstrated a grasping and lifting task with an object of 1.3 g and thickness of 250 $\mu$m at an operating voltage of 100 V. Finally, by taking advantage of the locomotion capabilities of HAMR, we demonstrate mobile manipulation by changing the position and orientation of small objects weighing up to 2.8 g controlled by the movement of the robot. We expect that the addition of this novel manipulation capability will increase the effectiveness of such miniature robots for accomplishing real-world tasks.

I. Introduction

Bio-inspired robots at the insect scale can reach confined environments and places inaccessible to humans [1] and therefore represent a great potential for mobile micromanipulation [2]. Their capabilities are evolving: microrobots have demonstrated the ability to fly [3], perch [4], swim [5], move on vertical or inverted surfaces [6], crawl on rough terrain [7], and even walk on water [8]. However, most research so far has focused more on the mobility [9] and control [10] of these robots, and less on their real world functionalities. For example, few of these small robots are able to perform complex tasks such as picking up objects and moving them to a desired location [11]. Adding such a capability could open up new possibilities such as depositing, collecting, and returning materials in inaccessible or remote environments [12]. In addition to object manipulation, microgrippers are expected to be useful as components of more complex mechanical mechanisms, such as clutches for devices that amplify the stroke of a primary actuator for frequency-leveraging [13].