Origami-inspired engineering enables reconfigurable, deployable structures valuable for soft robotics, yet integrating rigid components with soft materials remains challenging. Previous fabrication methods like over-molding or casting are error-prone, while actuation often relies on external motors, magnetics, or pneumatics, requiring bulky infrastructure. Early shape memory materials lacked reversibility, and recent liquid crystal elastomer systems using global heating offer poor spatial selectivity.
This paper addressed these gaps by introducing a layer-by-layer direct ink writing process that embeds flexible printed circuit boards into liquid crystal elastomer hinges, achieving integrated, localized Joule heating for precise, programmable, and repeatable self-folding without environmental control limitations.
Computational Design, Fabrication, and Control
The process begins with a computational design phase using custom software called OriCadLCE, where crease patterns are defined, folds are assigned as either mountain or valley hinges, and structural elements like stiffeners or adhesive tabs are integrated. The software automatically resolves geometric conflicts at tight vertices and generates complete tool paths for the printer, including pauses for inserting prefabricated sheets.
The fabrication itself employs a layer-by-layer direct ink writing method on a precision motion platform. A custom-synthesized liquid crystal elastomer ink is extruded through a fine nozzle, where the printing direction aligns the internal molecules to program the desired bending behavior. Between printed layers, flexible printed circuit board sheets are manually inserted and aligned using fixed pegs before being encapsulated by subsequent elastomer layers. After printing, the entire structure is cured under ultraviolet light to set the material properties.
Actuation of the completed robots is controlled digitally via a custom driver board featuring a constant-current laser driver and a microcontroller. This system enables precise control over the Joule heating traces embedded within each hinge, allowing for either fixed time-based sequences or closed-loop temperature feedback using onboard thermistors. Characterization of the hinges involved both passive oven heating for baseline comparisons and active integrated Joule heating to measure bending angles, torque, and cycle life. Motion capture software and thermal imaging were used to record rapid, repeatable folding sequences across various demonstrations, confirming the system's durability and precise digital control of complex shape changes.
System Performance and Experimental Results
The approach embeds custom-designed Flex-printed circuit boards (PCBs) within the printed elastomer layers, providing localized Joule heating for each hinge, integrated temperature sensing for closed-loop feedback, and large copper zones that thermally isolate individual folds. This allows selective and programmable activation of different hinge groups without environmental heating. Through systematic testing, a serpentine hinge geometry was identified as optimal, minimizing bending stiffness and achieving torque output comparable to traditional designs while ensuring strong mechanical encapsulation. It improved durability through adhesion to porous fiberglass stiffeners.
A unified computational design workflow, named OriCadLCE, was created to streamline the complex fabrication process. This software automatically resolves geometric conflicts, generates precise printing toolpaths, and exports vector files for both the elastomer printing and the Flex-PCB layout, ensuring all components fit together flawlessly. The digital control system, driven by a microcontroller and a constant-current driver, uses pulse-width modulation to adjust power to each hinge finely. Embedded thermistors enable proportional-integral-derivative feedback control, allowing for precise step-wise positioning and reliable, repeatable actuation sequences.
Endurance testing demonstrated remarkable robustness, with a hinge completing over 1,500 cycles of continuous operation with no visible performance degradation and low power consumption, making it suitable for untethered applications. The capabilities of this platform were validated through two complex demonstrations: a self-folding origami crane capable of independent wing flapping and body morphing, and a reconfigurable Miura sheet that transitions through multiple distinct geometric states.
These examples highlight the system's ability to encode multiple crease patterns and programmable behaviors within a single structure, establishing a powerful foundation for creating sophisticated, reconfigurable soft robotic systems.
Enabling Robust and Reconfigurable Origami Robotics
This work demonstrates a robust manufacturing approach for self-folding origami robots by embedding flexible printed circuit boards into 3D-printed liquid crystal elastomer hinges. This enables precise, digitally controlled, and reversible actuation via localized Joule heating without environmental dependencies.
The system exhibits high durability, surpassing 1500 cycles with minimal degradation, and showcases programmable behaviors in complex origami structures. By streamlining fabrication through a unified computational workflow, this method significantly expands the design space for soft-rigid hybrid robots and lays the groundwork for untethered, reconfigurable robotic systems and metamaterials.
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Journal Reference
Bershadsky, D. C., Zhao, T., Paulino, G. H., & Davidson, E. C. (2026). Digital Actuation Control of Soft Robotic Origami With Self-Folding Liquid Crystal Elastomer Hinges. Advanced Functional Materials. DOI:10.1002/adfm.202525150, https://advanced.onlinelibrary.wiley.com/doi/10.1002/adfm.202525150
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