MOMENTUM • VIRGINIA TECH MECHANICAL ENGINEERING 23 yet rigid enough to create adaptable machines that can perform different functions .”
To create a structure that could be morphed , the team turned to kirigami , the Japanese art of making shapes out of paper by cutting . This method differs from origami , which uses folding . By observing the strength of those kirigami patterns in rubbers and composites , the team was able to create a material architecture of a repeating geometric pattern .
Next , they needed a material that would hold shape but allow for that shape to be erased on demand . Here they introduced an endoskeleton made of a low melting point alloy ( LMPA ) embedded inside a rubber skin . Normally , when a metal is stretched too far , the metal becomes permanently bent , cracked , or stretched into a fixed , unusable shape . However , with this special metal embedded in rubber , the researchers turned this typical failure mechanism into a strength . When stretched , this composite would now hold a desired shape rapidly , perfect for soft morphing materials that can become instantly load bearing .
Finally , the material had to return the structure back to its original shape . Here , the team incorporated soft , tendril-like heaters next to the LMPA mesh . The heaters cause the metal to be converted to a liquid at 60 degrees Celsius ( 140 degrees Fahrenheit ), or 10 percent of the melting temperature of aluminum . The elastomer skin keeps the melted metal contained and in place , and then pulls the material back into the original shape , reversing the stretching , giving the composite what the researchers call “ reversible plasticity .” After the metal cools , it again contributes to holding the structure ’ s shape .
“ These composites have a metal endoskeleton embedded into a rubber with soft heaters , where the kirigami-inspired cuts define an array of metal beams . These cuts combined with the unique
Edward Barron , Michael Bartlett , and Dohgyu Hwang hold a piece of material that has been warped . Photo by Alex Parrish for Virginia Tech .