Shaping Soft Robotic Microactuators by Wire Electrical Discharge Grinding.

Edoardo Milana,Michaël De Volder,Dominiek Reynaerts,Jun Qian,Benjamin Gorissen,Mattia Bellotti

doi:10.3390/mi11070661

Abstract

Inflatable soft microactuators typically consist of an elastic material with an internal void that can be inflated to generate a deformation. A crucial feature of these actuators is the shape of ther inflatable void as it determines the bending motion. Due to fabrication limitations, low complex void geometries are the de facto standard, severely restricting attainable motions. This paper introduces wire electrical discharge grinding (WEDG) for shaping the inflatable void, increasing their complexity. This approach enables the creation of new deformation patterns and functionalities. The WEDG process is used to create various moulds to cast rubber microactuators. These microactuators are fabricated through a bonding-free micromoulding process, which is highly sensitive to the accuracy of the mould. The mould cavity (outside of the actuator) is defined by micromilling, whereas the mould insert (inner cavity of the actuator) is defined by WEDG. The deformation patterns are evaluated with a multi-segment linear bending model. The produced microactuators are also characterised and compared with respect to the morphology of the inner cavity. All microactuators have a cylindrical shape with a length of 8 mm and a diameter of 0.8 mm. Actuation tests at a maximum pressure of 50 kPa indicate that complex deformation patterns such as curling, differential bending or multi-points bending can be achieved.

Highlights

Soft robotic systems are capturing the interests of scientists and engineers with characteristics that are breaking with conventional robot traditions
Soft microrobotics has already been applied in microfluidics for making flexible active valves [11] and artificial cilia for biomimetic micromixing and micropumping [12]
wire electrical discharge grinding (WEDG) is used for machining axisymmetric microrods with more complex shapes to be placed in the internal cavity of inflatable soft robotic actuators in a micromoulding process

Summary

Introduction

Soft robotic systems are capturing the interests of scientists and engineers with characteristics that are breaking with conventional robot traditions. In order to circumvent these issues, we propose a bonding-free technique to fabricate millimetre-scaled soft bending microactuators, using out-of-plane moulding [18]. These microactuators consist of PDMS cylindrical structures with a simple cylindrical inflatable cavity, which is placed eccentric to the axis of the outer cylinder of the actuator. In this paper we introduce an additional manufacturing step to this bonding-free technique in order to fabricate more complex microactuators During this additional step, the cylindrical microrods are machined using a wire electrical discharge grinding (WEDG) process. WEDG is used for machining axisymmetric microrods with more complex shapes to be placed in the internal cavity of inflatable soft robotic actuators in a micromoulding process. V20), confocal microscopy (Sensofar® S lyn xE)staimndatsecdavnanluineg. electron microscopy (Phenom® Pro)

Moulding

Analytical Model

Microactuators Experimental Setup

Results and Discussions

Conclusions