In the 1960s, most computers took up an entire room. Faster computers now find themselves on the wrists of people all over the world.
As devices get smaller, humanity seems to be on track to create the sorts of machines that physicist Richard Feynman predicted in his 1959 talk, “Plenty of Room at the Bottom.” Feynman discussed the two main outcomes of technological progression: the miniaturization of information and ultimately, the miniaturization of machines. In order to get a step closer to achieving the second goal, researcher Marc Miskin developed a method for creating machines the size of human cells by taking inspiration from the Japanese art of origami.
Just like folding origami to create various complex shapes, these machines are capable of folding in on themselves to reproduce many simple shapes. To get a sense of just how small these devices are, about 100 million of these fit on a four inch wafer.
The material used to make this “origami machine” would have to have three properties: high flexibility, the ability to produce large force outputs and be electrically conductive. Miskin and his colleagues utilized graphene, a material made of carbon that is only one atom thick.
“Graphene is the stiffest, most flexible, most conductive material known to man. It was a natural choice,” Miskin said.
The team started with a layer of graphene and fused it with an equally thin layer of glass, making a complex that was about 20 atoms across. Though built flat, the glass layer attempts to expand when exposed to acid but is prevented from doing so by the graphene layer. To relieve the stress in the glass, the stack must bend, and this provides a route to making hinges and folds.
“This graphene/glass machine works when the glass expands relative to the graphene. This can happen when large ions, like acid molecules, enter the glass,” Miskin said.
Miskin believes that such machines will be important for biomedical applications.
“One of the smallest machines we’ve built is 15 microns across, so a tenth of a hair. At that size, you’re two times the size of a red blood cell, but a third the size of a nerve cell. If you can build an 8 micron machine and you inject it, it can go anywhere in your body,” Miskin said.
The act of drawing blood allows doctors to analyze blood for the presence of certain compounds by detecting their average concentration throughout the body. With small machines like these, more localized readings of chemical levels in the body can be obtained. Furthermore, a benefit to using graphene as the primary ingredient in these machines is that it is relatively biocompatible. Graphene is simply carbon, which is a natural constituent of the human body.
Miskin, however, insists that two major obstacles need to be resolved. The first is the sequence of folds that the graphene-glass complex undergoes.
“In principle, you could make just over 1 million folds per square inch. The issue is that they all have to fold at once in our current version and we are trying to fix that,” Miskin said.
For more complex shapes such as those similar to the origami crane, you cannot create the end product by making all of the necessary folds at once, there is a sequence of folds that must be followed. Furthermore, though the folding structure of these origami robots has been created, the sensors and other devices that would need to be attached to this structure to make more specialized machines present some difficulty.
“Scientists already know how to build the key sensors for biology at that size scale. We just don’t know how to package them up in a small space and deploy them. But this is what the technology we have developed opens the doors to,” Miskin said.
Correction: A previous version of this article incorrectly described the process through which the machines fold themselves.