The quest to give robots touch-sensitive artificial skin and develop medical prostheses with a sense of touch has shown much promise in recent years. The latest promising development comes out of Seoul National University's Multiscale Biomimetic Systems Laboratory where researchers have created a new biomimetic “electronic skin” that is inexpensive, yet sensitive enough to “feel” a drop of water.

Biomimetics is the school engineering that builds machines by imitating nature. Sometimes it’s something obvious, such as an ornithopter that flaps its wings like a bird. Some are less obvious, like hooks on a seed burr inspiring Velcro. Then there is Seoul National University’s approach of imitating the microscopic cilia found in ears, intestines and kidneys to create a touch-sensitive electromechanical skin that can detect something as light as a human pulse or a lady beetle walking across it.

The electronic skin is essentially a skin-like polymer that uses nanotechnology to incorporate a vast number of microscopic strain gauges. Compared to similar sensors, the design is very simple, yet extremely sensitive. The skin is actually two layers of polyurethane acrylate. The inner surface where the two layers meet is coated with the silicone polymer polydimethylsiloxane (PDMS). Sticking like hairs out of the PDMS is a forest of polymer nanofibers 100 nanometers in diameter (by comparison, a human hair is 60,000 nanometers in diameter) and 1,000 nanometers tall, which are coated with platinum.

The idea is that as the nanofibers mesh together they allow electrical currents to pass between the two layers. The nanofibers act like little potentiometers and they way that they mesh, rub or bend against one another alters the amount of current passed in that part of the skin. Touching pushing or twisting the skin places different kinds of strain on it, which the nanofibers detect and results in different electrical resistance patterns.

In this way, the skin can “feel” pressure, shear forces and torsion with great sensitivity. Furthermore, it can do this over and over again for up to 10,000 cycles, making this a very durable system. Additionally, unlike other touch sensors, such as those based on graphene, the nanofibers can detect strain in more than one direction.

It’s also very cheap to produce. According to the researchers the skin has no complex integrated nanomaterial assemblies or layered arrays. This means that the skin can be manufactured without costly manufacturing processes or exotic materials.

Sources: IEEE Spectrum

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