chinese scientists have given a foil paper doll the ability to do sit-ups by spiking a crystalline organic material with a polymer to make it more flexible. the polymer covalent organic framework – otherwise known as a polyCOF – was used by the scientists to build their version of an artificial muscle.


to make conventional COFs, scientists link simple carbon containing molecules with covalent bonds to make a porous crystalline powder. that crystalline structure imparts mechanical properties that are useful for catalysis, gas storage, and drug delivery, for example. but trying to make sheets or membranes using regular COFs is difficult because they are brittle and can’t bend without breaking.


the scientists recorded their findings in a new paper in ACS central science, wondering if they could improve cost mechanical properties by using linear polymers as one of the building blocks so they added polyethylene glycol into the reactant mix when building their COF compound. this made the final polyCOF much more malleable so that it could be twisted and stretched without damage.

paper doll can do sit-ups using 'artificial muscle' made from special polymer



the team also found that the polyCOF membranes responded to various chemical papers by folding up and then uncurling when placed back in normal air. to demonstrate how polyCOFs could be used as a type of artificial muscle, the team made a doll, using the membrane for the waist and aluminum foil for its other parts. when exposed to the ethynol vapours the doll sat up and when the vapors were withdrawn it laid back down again. the steps were repeated several times making the doll do sit-ups. the researchers say that the expansion of public health pours upon binding the gas likely explains the dolls calisthenics


actuators, or similar devices that mimic the contraction, expansion, and rotation of real muscle is a popular area of development for scientists. designboom has reported on other examples of artificial muscle that includes a electrically charged 3D printable soft muscle and an origami robot muscle that can life 1,000 times its own weight. they could be useful in a wide range of potential applications including robots, prosthetic limbs, powered exoskeletons, and even toys.


project info


published paper: polyCOFs: a new class of freestanding responsive covalent organic framework membranes with high mechanical performance

link: ACS central science, 2019. 10.1021/acscentsci.9b00212