A Flexible Fabrication Approach Toward the Shape Engineering of Microscale Soft Pneumatic Actuators

The recent developments of soft robots have inspired a variety of applications that require compliance for safety and softness for biomimetics. With such prevalence and advantages of soft robots, researchers are diverting their interests toward applications like micromanipulation of biological tissue. However, the progress has been thwarted by the difficulty in producing soft robots in miniature scale. In this paper, we present a new kind of microscale soft pneumatic actuators (SPA) made from streamlined and standardized fabrication procedure with customizable bending modalities inspired by shape engineering. Preliminary mathematical models are given to interpret width-based shape engineering for customization and to compare the bending angle and radius of curvature measured from the characterization experiments. The fabricated SPA was tested on the sciatic nerve of a rat in order to show its future potentials in biomedical field. Ultimately, this paper will contribute to the diversification of SPA fabrication and customization, as well as biomedical applications that demand smaller dimensions and higher precision.

I. Introduction

Soft robotics, as an emerging field, has provided a sound solution to safe interaction and bio-inspired mimicry [1]–[4]. Traditional rigid robots have the concerns of clashing, which is not desirable during interaction with delicate objects [2]. Regarding the safe interaction, the recent efforts have applied soft robotic technology to a variety of applications such as rehabilitation [4]–[8] and minimally invasive surgery (MIS) [2], [9]. Due to the advantage of innate compliance, interests are growing in utilizing soft robots to achieve microscale and delicate manipulations, which are usually required in surgeries that involve nerves and blood vessels. Traditionally, such applications rely on miniaturized instruments enabled by different mechanisms such as thermal actuation using SMA [10], Electroactive Polymers [11], electromagnetic [12] and pneumatic actuation [13]– [19]. However, safety concerns were invoked due to the drawbacks of those instruments: heating problem, complicated system and, most importantly, component rigidity. Among those existing solutions, pneumatically-driven actuators based on soft material seem to be the most suitable choice as the material and actuation media (compressed air) endow the actuators with innate softness while the whole structures remain relatively simple.