Imagine a digital tattoo that transmits skin temperature; a transparent sensor on a contact lens that tests for glaucoma; a pliable pacemaker wrapped around a beating heart; and an implant that controls pain after surgery, then dissolves harmlessly when it is no longer needed.
Each one is an experiment under way today in the biophysics of personal medicine.
At laboratories in the U.S., Switzerland, and Korea, bioengineers are developing unusually flexible ultrathin electronics that promise to free medical diagnostics from the clinical tethers of cables and power cords, to make measuring vital signs more intimate and effective. Unlike today’s rigid computer semiconductor chips, these bionics are designed to stretch, fold and bend without breaking. They are curvy and soft like much of the body itself.
“It is such a different way of thinking about electronics, making things stretchy,” said material scientist John A. Rogers at the University of Illinois at Urbana-Champaign who helped pioneer the technology. “There are a lot of things in human health care that we could do with these that are impossible today.”
A tattoo-like electronic thermometer from Northwestern University and the University of Illinois at Urbana-Champaign. Beckman Institute/University of Illinois at Urbana-Champaign
Rudimentary soft sensors are already edging into the market, incorporated into wrist bands that track exercise heart rate or as a wearable patch to sense head impact among athletes.
As more sophisticated medical applications become available during the next decade, these wireless devices will allow doctors and patients to monitor key health signs continuously, rather than only during periodic office or clinic visits, researchers said.
“It changes the game somewhat,” said biomedical engineer Fiorenzo Omenetto at Tufts University in Medford, Mass., who is among those developing biocompatible and biodegradable electronic medical devices.
It may be a decade before flexible electronic implants are approved for human use, but the digital skin patches promise to make vital sign monitors more portable and less obtrusive. Dr. Rogers and his colleagues reduced the equipment for a hospital electrocardiogram, which usually requires a monitoring device on a cart and a skein of connections, to an unobtrusive, wireless sensor that peels on and off like a Band-Aid. They also developed a wearable digital thermometer that is so sensitive it can sense minute changes in metabolism by measuring variations in body heat.
If need be, some experimental sensors can automatically dispense medication. Last month, researchers at Seoul National University in Korea reported that they created a digital skin patch, which can be worn on the wrist, aimed at movement disorders like Parkinson’s disease. It can store and transmit information about a patient’s movements, receive diagnostic information, and automatically dispense medication into the skin as needed, they reported in Nature Nanotechnology.
“Right now, people feel sick and they go to the hospital to get everything checked, but those tests are bulky and you can’t take them home,” said bioengineer Yonggang Huang at Northwestern University who collaborates with Dr. Rogers. “We want to make these devices as flexible and soft as human skin so they can be put on the skin and worn like a child’s tattoo.”
This month, Dr. Huang and his colleagues reported in Science that they had assembled off-the-shelf commercial components into a wireless stick-on digital skin patch that could monitor heart and brain activity as effectively as bulkier hospital equipment. They connected their microcircuits with tiny wires that fold and unfold in accordionlike pleats so the electronic patch could buckle, twist and flex without breaking.
A smart contact lens from the Swiss Federal Institute of Technology could monitor glaucoma. Swiss Federal Institute of Technology
At the Swiss Federal Institute of Technology in Zurich, electrical engineer Giovanni Salvatore and his colleagues are fabricating even thinner complex circuits so elastic that they can be wrapped around a strand of human hair without cracking or short-circuiting.
His research group is building transparent circuits on a membrane of a polymer plastic called parylene that is 1-micron thick. As a pilot project, they built a see-through strain gauge to monitor the buildup of pressure in the eye and mounted it on a contact lens. They also are developing a digital tattoo that can monitor heart rate and transmit the data wirelessly to a cellphone.
“The focus of the research is to make these ultra-flexible electronics that can be mounted on the skin or the body,” said Dr. Salvatore.
And unlike conventional electronics that are built to last indefinitely, some of these experimental devices are biodegradable. Indeed, researchers are testing some medical diagnostic devices that can be programmed to vanish on schedule, completely and harmlessly dissolving in water or body fluids after days, months, or years.
“There are a lot of devices that you would like to implant in the body that don’t need to function forever—a process for wound-healing, the healing of a bone, or the treatment of a cancerous tumor,” said Dr. Rogers. “You would like to have some programmable electronic device but you would only need it for weeks or months.”
To make vanishing medical implants, the researchers crafted electronic circuits from cocoon silk, thin sheets of porous silicon and magnesium electrodes—materials all capable of resorbing into the body. The materials aren’t toxic and the quantities are smaller than those in the average vitamin supplement, the scientists said.
Add water and the circuits simply melt.
A smart bandage by researchers at Seoul National University can record muscle activity and trigger the release of a drug. Donghee Son/Jongha Lee
They use the silk to enclose and waterproof the circuit. They program the device to dissolve on schedule by varying the strength of the bonds between the silk molecules and by the thickness of the circuit itself. “We make these micro-Ziploc [bags], so you have to melt the Ziploc [bag] and then the device,” said Dr. Omenetto at Tufts.
They tested the device as a biomedical implant in mice, using it to deliver a bactericide drug to surgical wound sites in the animals. The implant vanished on schedule, leaving only a faint residue of silk. That too was harmlessly absorbed into the body, they said.
“The idea is to make the electronics disappear by themselves when you no longer need it,” Dr. Huang said. “All this technology has been demonstrated successfully on animal models. To really apply this to humans may be a long process.”
Source: http://online.wsj.com/news/articles/SB10001424052702303825604579515704230508572?mod=e2fb
