Monday, 12 November 2012

Cyberpunk here we come! Synthetic skin

Synthetic, Self-Healing Skin That's Sensitive To The Touch

Human skin is a hard system to emulate, but that hasn't stopped Stanford scientists from producing a touch-sensitive material that can heal itself at room temperature.

By Clay DillowPosted 11.12.2012 at 12:01 pm0 Comments

Self-Healing, Touch-Sensitive Synthetic Skin Linda A. Cicero, Stanford News Service

Before we can construct the realistic humanoid robots that populate our most vivid sci-fi-driven dreams, there are a lot of human systems that researchers are going to have to emulate synthetically. Not the least challenging is human skin; filled with nerve endings and able to heal itself over time, our skin serves as both a massive sensory system and a barrier between our innards and the outside world. Now, an interdisciplinary team of Stanford researchers has created the first synthetic material that is both self-healing at room temperature and sensitive to touch--a breakthrough that could be the beginnings of a new kind of robot skin (and in the meantime enjoy much more practical applications like enhanced prosthetics).

The Stanford material is far from the first self-healing plastic or polymer, but it does enjoy some benefits that set it apart. For one, many self-healing materials require some kind of catalyst or special condition to heal up, things like exposure to high temperature or certain spectrums of light. Others can heal up at room temperature, but they generally can only do so once--the act of healing alters their chemical structure such that they cannot do it a second time, much less a third or fourth.

Then, if an analog for skin is what you’re truly looking for, there’s the problem with touch sensitivity. Most plastics, polymers, and such--the primary materials used in self-healing research--are fantastic insulators. But to imbue a material with a sense of touch--and to make it interface with a larger digital system--you really want something conductive. That’s where the Stanford team has really broken new ground. Its material can repair cuts or tears in itself at room temperature multiple times, and it is conductive.

How did the researchers pull it off? They started with a plastic consisting of molecular chains joined by simple hydrogen bonds. This imparts the self-healing ability, as the bonds can be easily broken but also easily reconstituted by simply putting the broken chains back in contact with each other. In the lab, the researchers severed a piece of the material completely, creating two separate halves. After pressing the cut edge back together for just a few seconds, three-quarters of its prior strength had been restored. Within half an hour it returned to nearly 100 percent strength. After 50 such trials, the material still healed up nicely.

Then, to achieve conductivity, the researchers distributed nickel particles throughout their plastic. These nickel particles not only increase the material’s mechanical strength, but also serve as a means for electrons to move through the material, hopping from one particle to the next, creating an electric current. Bending, flexing, or otherwise warping the material changes the distance between the nickel particles, altering the material's resistance to the current. That electrical resistance can be measured to determine the shape of the skin and any pressure being exerted on it.

It’s easy to envision something like this being integrated into future prosthetics to help restore a sense of touch to those missing a limb. More immediately, such a material could be used to sheathe other electronics to give them a self-healing capacity. The findings were published in the November 11 issue of the journal Nature Nanotechnology.

Saturday, 13 August 2011

Electronic Skin

Someday soon, hospital patients won’t be hooked up to wires and monitors -- instead, electronic patches will be temporarily tattooed onto their bodies. Doctors will be able to monitor their vital signs without poking and prodding, and patients wearing neck patches will even be able to communicate with robots, who will translate throat muscle movements into simple speech.

A new electronic skin patch, no more invasive than a temporary tattoo, marks a major breakthrough in human-machine interfaces. Tiny semiconductor circuits that stretch with the skin could be rubbed onto a person’s skin to monitor muscle activity, heart activity or even brain waves in real time without using bulky medical equipment.

The epidermal electronic circuit is initially mounted on a super-thin sheet of soluble plastic and laminated onto the skin with water, just like a temporary tattoo. Once it’s on, it can bend, wrinkle and stretch along with a wearer’s skin — it doesn’t pop off or snap, which is no small feat considering this is a high-performance semiconductor. When it’s no longer needed, it peels off like a layer of sunburned skin. Check out the video below to see this in action.

The devices adhere to the skin not with glue or static electricity, but close-contact atomic forces called van der Waals interactions, which are essentially invisible to the user. Adhesion lasts up to 24 hours, the researchers report.

Researchers at the University of Illinois who came up with this device made circuits with a wide array of components, to prove it could work: sensors, LEDs, transistors, radio frequency capacitors and wireless antennas, according to UI. The devices can draw power from induction or even from mini solar cells.

Inventors say they could be used for various medical applications, especially sensors that monitor heart and muscle activity, which currently require conductive gels, tape and wires. To prove it, they measured electrical activity produced by the heart, brain, and skeletal muscles, they report in this week’s issue of the journal Science.

Studying brain function in a normal environment is impossible now — to use an EEG, a patient would have to be in a lab setting or wear some type of complicated helmet — but the patch could make it possible. Or imagine a patient with a degenerative disease who cannot communicate, but could use the patches to connect with a computer.

In a throat patch experiment, the patch was precise enough for the research team to differentiate several words, according to the National Science Foundation. They were even able to control a voice-activated video game with better than 90 percent accuracy.

“The technology can connect you to the physical world and the cyberworld in a very natural way that feels very comfortable,” said UI electrical and computer engineering professor Todd Coleman, who co-led the research team.

The circuits are made possible through novel fabrication methods that allow bendable versions of semiconductors that are brittle when in bulk form. The research team, which also included engineering researchers at Northwestern University, developed a new device geometry they call “filamentary serpentine,” according to a UI news release. The circuits of the various devices are fabricated as tiny, squiggled wires, as shown in the photo above. The circuits’ wavy shape allows them to bend, twist, scrunch and stretch while maintaining functionality.

“The blurring of electronics and biology is really the key point here,” said Northwestern engineering professor Yonggang Huang. “All established forms of electronics are hard, rigid. Biology is soft, elastic. It's two different worlds. This is a way to truly integrate them.”

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	Video: Self-Healing Electronics Use Liquid Metal to Fix Broken Circuits
	Video: Self-Healing Polymer Fixes Itself Under Ultraviolet Light

	Artificial Skin Gets a Solar-Powered Upgrade
	New Electric Skin Could Bring the Human Touch to Robots, Artificial Limbs
	Optical Sensors in Robots' Skin Give Them A Softer Touch