Fast‐Response, Stiffness‐Tunable Soft Actuator by Hybrid Multimaterial 3D Printing

Abstract

Soft robots have the appealing advantages of being highly flexible and adaptive to complex environments. However, the low‐stiffness nature of the constituent materials makes soft robotic systems incompetent in tasks requiring relatively high load capacity. Despite recent attempts to develop stiffness‐tunable soft actuators by employing variable stiffness materials and structures, the reported stiffness‐tunable actuators generally suffer from limitations including slow responses, small deformations, and difficulties in fabrication with microfeatures. This work presents a paradigm to design and manufacture fast‐response, stiffness‐tunable (FRST) soft actuators via hybrid multimaterial 3D printing. The integration of a shape memory polymer layer into the fully printed actuator body enhances its stiffness by up to 120 times without sacrificing flexibility and adaptivity. The printed Joule‐heating circuit and fluidic cooling microchannel enable fast heating and cooling rates and allow the FRST actuator to complete a softening–stiffening cycle within 32 s. Numerical simulations are used to optimize the load capacity and thermal rates. The high load capacity and shape adaptivity of the FRST actuator are finally demonstrated by a robotic gripper with three FRST actuators that can grasp and lift objects with arbitrary shapes and various weights spanning from less than 10 g to up to 1.5 kg.

Hybrid Living Materials: Digital Design and Fabrication of 3D Multimaterial Structures with Programmable Biohybrid Surfaces

“…This work thus advances biohybrid materials toward applications ranging from wearable therapeutics or monitoring devices to customizable consumer products. [95][96][97]…”

Multi-Material 3D Printed Shape Memory Polymer with Tunable Melting and Glass Transition Temperature Activated by Heat or Light

“…SMPs, with activation triggered by heat, have been widely studied. The activation trigger can be direct heating [6][7][8][9][10], electric [11][12][13], magnetic fields [14,15] or light [16,17]. The advantage of magnetic and light activations is that they can be performed remotely, without the need of direct contact or wiring.…”

“…For magnetic triggering, there is usually a need for a strong magnetic field induced by a robust electromagnet or magnet, while for light activation, a compact simple light source is sufficiently efficient. A variety of 3D printing methods have been demonstrated over the years for SMP materials, including extrusion-based methods, such as fused modeling deposition (FDM) [8,9,15,17], direct ink writing (DIW) [7,11,12] and stereolithography (SLA) approaches, including laser sintering [6], Polyjet technology [13,18] and digital light processing (DLP, also known as vat polymerization printing) [10,[19][20][21]. An advantage of SLA is the possibility of printing with high resolution, which makes it a very favorable method for building various functional 3D objects.…”

A Unidirectional Soft Dielectric Elastomer Actuator Enabled by Built-In Honeycomb Metastructures

“…Soft actuators, typically made of compliant materials that are responsive to external physical stimuli, play a key role in enabling the functionalities of soft robots. Various actuation technologies has been developed, such as pneumatic or hydraulic actuators [7][8][9], shape memory polymers [10][11][12], ionic polymer-metal composites [13] and so on. Among them, dielectric elastomer actuators (DEAs) are a promising alternative because of their advantages such as fast response, high energy density and low cost [14][15][16][17][18].…”