They develop a material that can take and maintain any shape
Researchers from the School of Engineering and Sciences Applied (SEAS) of Harvard John A. Paulson have developed a shape-shifting material and it can take and hold any shape possible.
This breakthrough paves the way for a new type of multifunctional material that could be used in a range of applications, from robotics and biotechnology to architecture. The research is published in the Proceedings of the National Academy of Sciences.
"Today's shapeshifting materials and structures can only transition between a few stable configurations, but we have shown how to create structural materials that have an arbitrary range of shapeshifting capabilities," he said in a statement. L Mahadevan, Professor of Mathematics Applied, of biology Organismic and Evolutionary, and Physical and main author of the article. "These structures allow independent control of geometry and mechanics, laying the foundation for designing functional forms using a new type of transformable unit cell."
One of the biggest challenges in designing shape-shifting materials is balancing the seemingly conflicting needs for formability and stiffness. The adaptability allows transformation to new shapes, but if you are too compliant, you can't keep the shapes stable. The stiffness helps to lock the material in place, but if it is too stiff, it cannot take new forms.
The team started with a neutrally stable unit cell with two rigid elements, a strut and a lever, and two stretchable elastic springs. If you've ever seen the beginning of a Pixar movie, you've seen neutrally stable footage. The head of the lamp Pixar it is stable in any position because the force of gravity is always counteracted by springs that are stretched and compressed in a coordinated way, regardless of the configuration of the lamp. In general, neutrally stable systems, a combination of rigid and elastic elements balances the energy of the cells, making each one of them neutrally stable, which means that they can move between an infinite number of positions or orientations and be stable in any of them.
"By having a neutrally stable unit cell, we can separate the geometry of the material from its mechanical response both individually and collectively," he said. Gaurav Chaudhary, Postdoctoral fellow at SEAS and co-first author of the article. "The geometry of the unit cell can be varied by changing both its overall size and the length of the single moving strut, while its elastic response can be changed by varying the stiffness of the springs within the structure or the length of the struts and links."
The researchers called the set "totimorphic materials"Due to its ability to transform into any stable form. The researchers connected individual unit cells with naturally stable joints, building 2-D and 3-D structures from individual totimorphic cells.
The researchers used mathematical models and real-world proofs to show the shape-shifting ability of the material.
The team showed that a single sheet of totimorphic cells can curl, spin on a propeller, transform into the shape of two distinct faces and even bear weight.
"We show that we can assemble these elements into structures that can take any shape with heterogeneous mechanical responses," said S. Ganga Prasath, a postdoctoral fellow at SEAS and co-first author of the paper. "Since these materials are based on geometry, they could be scaled down to be used as sensors in robotics or biotechnology or they could be expanded to be used on an architectural scale.
"Together, these totimorphs pave the way for a new class of materials whose response to deformation can be controlled at multiple scales"said Mahadevan.
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