Sculpting Soft Machines

Abstract

This article describes an easily accessed manufacturing process for soft actuators. It does not require molds and uses safe, readily available materials: table salt and rubber molding compounds. This process involves sculpting or casting uncured rubber compounds and results in soft, open-cell foam structures, which can be sealed to form actuators. The foams have low elastic moduli ranging from 20 to 30 kPa, large ultimate strains over 3.5, and rapid fluid transport rates up to 30 L min−1 cm−2. To demonstrate the capabilities of this process, we sculpted a simple bending actuator, a gripper, and many other 3D shapes. Blocked-force measurements demonstrated that the simple bending actuator can exert up to 5 N of force at its tip, and the gripper picked up a 200 g object. This technique could enable engineers of all ages and skill levels to engage in soft robot fabrication, contributing to K-12 STEM education. In addition, the proposed manufacturing technique could be also interesting for the STEAM (Science, Technology, Engineering, Arts, and Mathematics) community, thus combining science and arts. In addition, this work has the potential to inspire a new, more inventive form of engineering by combining the artistic practice of free-form sculpting with robot fabrication.