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Whenever we think about a machine we think about something stiff, with hard surfaces. This goes back to the first machines, the steam looms, in the XVIII century and ever since machines have been made with iron, steel and other materials that are stiff. On the other hand, you, me and most of living beings are soft.
We have soft materials, plenty of them actually (just think at your couch or to a doll…), but these soft materials do not mix well with electronics where you have silicon and copper (or other metals). Embedding silicon is ok as long as you are not stretching part of the circuits.
In these posts I have often reported on some inventions that can result in "plastic electronics" but all of them are about embedding a small circuit in a soft material. Nothing like having a soft material doubling up as an electronic circuit.
This is what this news from Purdue university is all about.
Rebecca Kramer, an assistant professor of mechanical engineering at Purdue University is working with her research team to develop a fabrication technique that can result in soft materials that can also be used as electronic circuit (in a broad sense, the first target is to be able to have the surface of the material covered by electronic sensors, like our skin -well in our skin we do not have "electronic" sensors but you get the gist).
They start with a silicon based "elastomer" (if you are curious it is a polydimethylsiloxane, a rubber like polymer) and embed in it liquid-alloy (indium-gallium) patterns of lines to create a network of sensors. The use gallium oxide that has very high structural stability, which means that the thin layer formed on the surface will keep its structure even if the surface bends and stretches. Liquid alloy is encased in two layers of gallium oxide and it acts like a sensor gauging the stress level of the surface. Since the sensor is made of liquid it can conform to any bending and stretching and it is able to measure up to 100% material strain (vs the 1% that can be measured by rigid metal film sensors).
To give an understandable comparison the skin covering our joints can sustain up to 50% strain as we bend our limbs. By using the elastomers created by researchers at Purdue you can measure the strain in your joints by embedding them in the fabric of your clothes.
Also, you may expect that future version of Asimov, the Honda robot, may look much more human like, as its skin can be made of soft materials, rather than with the plastic and metal of today.
