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Silicone elastomers are widely used in biomedical devices and soft machines because of their compliance, inertness, and biocompatibility. Their sol-gel transition during curing enables mold casting and layer-by-layer manufacturing, allowing the fabrication of fully elastomeric and hybrid soft-rigid devices. However, controlling adhesion at material interfaces remains elusive, especially under diverse temperature conditions. This study introduces a framework that relates adhesion strength to a dimensionless reaction coordinate coupling time and temperature. This reaction coordinate can be used to predict the transition from bulk fracture to adhesive failure, which is crucial to create robust devices with strong interfaces. Using this framework, we fabricated elastomeric robotic actuators and demonstrated 3D printing with direct ink writing. The actuators achieved 50% higher curvature with the same design, and the 3D-printed parts exhibited over 200% improvement in interlayer adhesion. This work serves as a tool for optimizing interfacial adhesion for soft materials across different fabrication approaches.
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This content will become publicly available on March 23, 2027
Pellet Printing for Soft Robotic Devices
ABSTRACT Rapid prototyping of soft robotic devices is often constrained by manual fabrication or additive manufacturing methods that are limited in material choice or require extensive post‐processing. Fused Granulate Fabrication offers a scalable alternative by extruding thermoplastic pellets through a screw‐based extruder, enabling continuous, high‐throughput printing and access to a broad range of commercially available materials, from rigid plastics to silicone‐soft elastomers with Shore hardness as low as 6A. Reliable 3D printing of airtight pneumatic soft structures at volumetric flow rates up to 5 mm3/s is demonstrated by addressing inconsistent extrusion and stringing issues through a combination of hardware optimization and a materials‐centered printing strategy. Extrusion and oozing tests are used to construct material‐specific oozing performance profiles, establishing practical guidelines for material selection in FGF printing, and are linked to key rheological descriptors. The mechanical performance of thermoplastic styrenic block copolymer pellets is characterized, revealing Mullins‐effect‐induced softening, and fabricated pneumatic actuators exhibit durability exceeding 100 000 bending cycles. Demonstrations include a pneumatically actuated robotic hand, a multi‐chamber robotic fish, and a soft pressure cuff. FGF enables the digital fabrication of large‐scale, airtight soft robotic devices using commercially available thermoplastic pellets, providing a versatile, cost‐effective, and scalable alternative to soft lithography with mechanical performance comparable to silicone elastomers.
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- Award ID(s):
- 2512999
- PAR ID:
- 10701694
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Advanced Science
- Volume:
- 13
- Issue:
- 30
- ISSN:
- 2198-3844
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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