Smart 'Band-Aid' Senses, Lights Up And Delivers Medicine

Smart 'Band-Aid' Senses, Lights Up And Delivers Medicine
A new stretchy hydrogel can be embedded with various
electronics. Here, a sheet of hydrogel is bonded to a matrix
of polymer islands (red) that can encapsulate electronic
components such as semiconductor chips, LED lights,
and temperature sensors. (Credit: Melanie Gonick/MIT)
MIT engineers have designed what may be the Band-Aid of the future: a sticky, stretchy, gel-like material that can incorporate temperature sensors, LED lights, and other electronics, as well as tiny, drug-delivering reservoirs and channels. The "smart wound dressing" releases medicine in response to changes in skin temperature and can be designed to light up if, say, medicine is running low.
When the dressing is applied to a highly flexible area, such as the elbow or knee, it stretches with the body, keeping the embedded electronics functional and intact.
The key to the design is a hydrogel matrix designed by Xuanhe Zhao, Associate Professor in MIT's Department of Mechanical Engineering. The hydrogel, which Zhao detailed earlier, is a rubbery material, mostly composed of water, designed to bond strongly to surfaces such as gold, titanium, aluminum, silicon, glass, and ceramic.
In a new paper published in the journal Advanced Materials, the team reports embedding various electronics within the hydrogel, such as conductive wires, semiconductor chips, LED lights, and temperature sensors. Zhao says electronics coated in hydrogel may be used not just on the surface of the skin but also inside the body, for example as implanted, biocompatible glucose sensors, or even soft, compliant neural probes.
"Electronics are usually hard and dry, but the human body is soft and wet. These two systems have drastically different properties," Zhao says. "If you want to put electronics in close contact with the human body for applications such as health care monitoring and drug delivery, it is highly desirable to make the electronic devices soft and stretchable to fit the environment of the human body. That's the motivation for stretchable hydrogel electronics."
A strong and stretchy bond
Typical synthetic hydrogels are brittle, barely stretchable, and adhere weakly to other surfaces. To get around these challenges, the researchers came up with a design strategy for robust hydrogels, mixing water with a small amount of selected biopolymers to create soft, stretchy materials with a stiffness of 10 to 100 kilopascals - about the range of human soft tissues.
In the new study, the researchers applied their techniques to demonstrate several uses for the hydrogel, including encapsulating a titanium wire to form a transparent, stretchable conductor. In experiments, they stretched the encapsulated wire multiple times and found it maintained constant electrical conductivity.
Zhao also created an array of LED lights embedded in a sheet of hydrogel. When attached to different regions of the body, the array continued working, even when stretched across highly deformable areas such as the knee and elbow.
A versatile matrix
Finally, the group embedded various electronic components within a sheet of hydrogel to create a "smart wound dressing," comprising regularly spaced temperature sensors and tiny drug reservoirs. The researchers also created pathways for drugs to flow through the hydrogel, by either inserting patterned tubes or drilling tiny holes through the matrix. They placed the dressing over various regions of the body and found that even when highly stretched the dressing continued to monitor skin temperature and release drugs according to the sensor readings.
The researchers believe an immediate application of the technology may be as a stretchable, on-demand treatment for burns or other skin conditions. Delving deeper, they envisions hydrogel to be an ideal, biocompatible vehicle for delivering electronics inside the body. They are currently exploring hydrogel's potential as a carrier for glucose sensors as well as neural probes.

Based on material originally posted by Massachusetts Institute of Technology.