Support-free fabrication of elastic silicone microstructures via direct ink writing for soft robotic applications

Abstract Elastic micro–nano structures with complex features (e.g. overhangs, bridges, porous lattices) are vital for soft robotics, flexible sensing, and biomedical devices, yet their fabrication faces challenges of support-material residue and gravitational deformation. This paper presents a support-free direct ink writing 3D printing strategy for elastic silicone microstructures by precisely regulating material yield strength to exceed structural maximum stress. The method enables large-span self-supporting structures (up to 10 mm), including cantilevers and hollow cylinders, without external supports. A quantitative model links process parameters (speed, pressure, layer height) to line width, and a hyperelastic silicone material with exceptional strain tolerance (514%) and notch resistance is developed. As an application demonstration, flexible sensors are integrated into 3D-printed grippers, enabling real-time feedback during object manipulation. Validated via an industrial robotic arm, the gripper stably handles fragile irregular objects (e.g. eggs and cherry tomatoes) with rapid response (0.6 s). This work establishes a scalable paradigm for manufacturing self-supporting elastic microstructures in soft robotics and precision applications.