Opportunity
The field of 4D printing, particularly using responsive hydrogel materials, holds immense promise for applications in soft robotics, actuators, and biomedical devices. Hydrogels are especially attractive for biomedical uses due to their softness, biocompatibility, and responsiveness. However, existing 4D-printed hydrogel systems face significant limitations. A primary challenge is their relatively slow deformation speed, which is constrained by the inherent kinetics of hydration and dehydration processes. Furthermore, while magnetic-driven 4D printing offers advantages like fast response, untethered control, and excellent biocompatibility for remote actuation in confined spaces, integrating this capability with programmable 4D shape deformation into a single, cohesive actuator remains difficult. There is a clear and unmet need for a fabrication technique that can produce advanced actuators capable of both pre-programmed, reversible shape transformations and wireless, remotely controlled locomotion to operate effectively in complex and challenging environments.
Technology
This patent introduces an innovative 4D printing strategy to create a dual-responsive actuator (DRA) that addresses the existing challenges. The core innovation is a bilayer structure fabricated via direct 4D printing. This structure consists of a hydrogel film (e.g., made from chitin, cellulose, or GelMA) and numerous magnetic elastomer filaments (e.g., PDMS embedded with NdFeB particles) printed on top of it. The technology leverages the differential swelling properties between the two layers. When exposed to humidity, the hydrogel film swells significantly (swelling ratio ~1.07) while the magnetic elastomer remains nearly unchanged (swelling ratio ~0.01), causing a mismatch that drives the 2D flat structure to twist into a programmable 3D helical or tubular shape. This humidity-induced deformation is reversible through dehydration. Concurrently, the embedded magnetic particles allow the actuator to respond to external magnetic fields. Upon application of a magnetic field, the pre-magnetized actuator rapidly deforms further, contracting the helix to a smaller, pre-designed configuration. The degree of both deformations is highly controllable: the initial helical shape can be programmed by varying the printing angle (0° to 90°) of the magnetic filaments on the hydrogel, and the magnetic contraction can be tuned by adjusting the magnetic field intensity. This combination enables seamless, reversible transitions between shapes and motion modes.
Advantages
- Dual Responsiveness: The actuator uniquely responds to both humidity and magnetic stimuli, enabling complex, multi-stage transformations.
- Programmable Deformation: The final 3D helix structures and their deformation extent are programmable through the design of the printing pattern (angles) and magnetic field parameters.
- Fast and Reversible Actuation: Magnetic actuation provides rapid response and contraction, while the humidity-driven deformation is fully reversible, offering excellent cyclic stability.
- Untethered and Remote Control: Magnetic control allows for wireless, remote navigation and manipulation in enclosed or hard-to-reach spaces.
- Versatile Locomotion: Under magnetic field control, the actuator can switch between distinct motion modes such as rolling and wriggling, enhancing mobility in complex terrains.
- Biomedical Functionality: The hydrogel component allows for drug loading, enabling potential applications like drug-eluting stents with combined expansion and therapeutic release capabilities.
- Strong Interface Adhesion: The fabrication process ensures robust adhesion between the hydrogel and elastomer layers, which is critical for reliable and repeatable deformation.
Applications
- Soft Robotics: For creating untethered, small-scale robots capable of navigating confined spaces, overcoming obstacles, and performing tasks in hazardous environments.
- Biomedical Devices: As smart, minimally invasive surgical tools or exploratory capsules for procedures within the gastrointestinal tract or other body cavities.
- Drug-Eluting Vascular Stents: As an expandable stent that can be magnetically navigated to a stenosis site, expanded to open the vessel, and locally release therapeutic agents.
- Smart Actuators and Sensors: In adaptive systems that change shape or function in response to environmental humidity or remote magnetic signals.
- Harsh Environment Operation: For remote operation in challenging conditions such as enclosed pipelines, viscous fluid surfaces, or on sloped and uneven terrains.
