A method was developed for massproducing tiny robots no bigger than a cell. The microscopic devices, called “syncells” (short for synthetic cells), might eventually be used to monitor conditions inside an oil or gas pipeline, or to search out disease while floating through the bloodstream.
The key to making the devices in large quantities lies in a method developed for controlling the natural fracturing process of atomically thin, brittle materials, directing the fracture lines so that they produce miniscule pockets of a predictable size and shape. Embedded inside these pockets are electronic circuits and materials that can collect, record, and output data.
The novel process, called “autoperforation,” uses a two-dimensional form of graphene, which forms the outer structure of the syncells. One layer of the material is laid down on a surface, then tiny dots of a polymer material containing the electronics for the devices are deposited by a laboratory version of an inkjet printer. Then, a second layer of graphene is laid on top.
Graphene, an ultrathin but extremely strong material, is brittle but rather than posing a problem, the brittleness was used as an advantage. The new system controls the fracturing process so that rather than generating random shards of material, like the remains of a broken window, it produces pieces of uniform shape and size. When the top layer of graphene is placed over the array of polymer dots — which form round pillar shapes — the places where the graphene drapes over the round edges of the pillars form lines of high strain in the material. As a result, the fractures are concentrated right along those boundaries. The graphene will completely fracture, but the fracture will be guided around the periphery of the pillar. The result is a neat, round piece of graphene that looks as if it had been cleanly cut out by a microscopic hole punch.
Because there are two layers of graphene, above and below the polymer pillars, the two resulting disks adhere at their edges to form something like a tiny pita bread pocket, with the polymer sealed inside. Other two-dimensional materials, such as molybdenum disulfide and hexagonal boronitride, work as well.
The general procedure of using controlled fracture as a production method can be extended across many length scales and potentially can be used with essentially any 2D materials. The process is one of the only ways available to produce standalone integrated microelectronics on a large scale that can function as independent, free-floating devices. Depending on the nature of the electronics inside, the devices could be provided with capabilities for movement, detection of various chemicals or other parameters, and memory storage.