The team filled individual internal cells with a blend of gallium and iron that is solid at room temperature but liquefies when heated electrically. By sending current through specific cells, the researchers can liquefy any desired pattern, effectively encoding a map of soft and stiff regions in the material in a way that resembles writing bits in digital storage. Cooling the material returns the liquefied cells to a solid state, preserving the programmed mechanical configuration until the pattern is changed again.
In thin two-dimensional sheets, this digital composite architecture enables precise tuning of stiffness and energy dissipation across a wide range, allowing the sheets to mimic materials from relatively rigid plastics to softer rubbers. Because the underlying structure remains the same, engineers can iterate through many mechanical profiles without reprinting or remanufacturing parts. The team subjected these programmable sheets to extensive testing to quantify how different solid-liquid patterns translate into bulk mechanical responses.
The concept extends further in three dimensions, where the group created modular, Lego-like blocks that can be assembled and disassembled. Each cubic block resembles a Rubik's cube, containing 27 individually addressable cells that can be locally liquefied with electrical signals. Arranging multiple blocks into larger structures produces three-dimensional assemblies whose stiffness distributions can be reprogrammed, opening the door to adaptable load-bearing and motion-control components.
To demonstrate a potential application in soft robotics, the researchers joined 10 of these programmable cubes into a straight column that functioned as a tail for a simple robotic fish. They attached the tail to a basic motor and operated the motor identically while varying which cells in the tail were solid or liquid. The same robotic fish exhibited very different swimming trajectories depending on the internal phase pattern of the tail, showing how reconfigurable mechanical architectures can reroute motion without changing the actuator.
Lead author and PhD student Yun Bai described the goal as creating materials that behave more like living tissue than static machine parts. "We want to make materials that are alive," Bai said. He explained that while 3D printers can produce parts with fixed mechanical properties, achieving a new behavior normally requires printing a new object. In contrast, the digital composite approach lets a single object assume many mechanical personalities by reassigning which cells are solid and which are liquid in real time.
Assistant professor Xiaoyue Ni, who led the research group, said the ultimate aim is to scale these concepts into larger, more capable systems. The team envisions miniaturized versions of the programmable blocks that could operate in confined environments such as blood vessels, where a device might stiffen for propulsion and soften to avoid damaging tissue. Similar ideas could apply inside delicate electronic systems, where reconfigurable supports or vibration isolators might adapt to changing loads and conditions.
Another avenue involves tailoring the metal mixture to adjust melting and freezing points for specific environments, including the human body. By selecting alloys that transition at biocompatible temperatures, designers could create implantable components that reconfigure in situ, for example to act as adaptive stents that change stiffness or shape as a vessel remodels. Outside biomedicine, robotic platforms that traverse varied terrains or manipulate fragile objects could benefit from limbs and grippers whose mechanical profiles update on demand.
Ni said the broader vision is to build flexible, programmable materials that serve as the foundational elements of future robotic systems. Instead of treating structure and actuation as separate design problems, engineers could co-design mechanical architectures and control schemes so that a robot's body actively participates in its behavior. The digital composite strategy provides a route to such embodied adaptability by combining simple electrical inputs with reversible phase transitions at the material level.
The work relied on facilities at the Duke University Shared Materials Instrumentation Facility, which is part of the North Carolina Research Triangle Nanotechnology Network supported by the U.S. National Science Foundation under grant ECCS-2025064. Additional support came from the Beyond the Horizon Initiative of the Pratt School of Engineering at Duke University. The study, titled "Digital composites with reprogrammable phase architectures," was published online on January 23, 2026, in the journal Science Advances.
Research Report:Digital composites with reprogrammable phase architectures
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