Engineers create ‘smart wound dressing’

Sheet of hydrogel bonded to

a matrix of polymer islands

(red) that can encapsulate

electronic components

Photo by Melanie Gonick/MIT

Engineers say they have designed “smart wound dressing,” 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 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, PhD, of the Massachusetts Institute of Technology in Cambridge.

The hydrogel, which was describe in Nature Materials last month, 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 paper published in Advanced Materials, Dr Zhao and his colleagues described embedding various electronics within the hydrogel, such as conductive wires, semiconductor chips, LED lights, and temperature sensors.

Dr Zhao said 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,” Dr Zhao said. “These two systems have drastically different properties. If you want to put electronics in close contact with the human body for applications such as healthcare 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.

“They’re often used as degradable biomaterials at the current stage,” Dr Zhao said. “If you want to make an electronic device out of hydrogels, you need to think of long-term stability of the hydrogels and interfaces.”

To get around these challenges, his team 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. The researchers also devised a method to strongly bond the hydrogel to various nonporous surfaces.

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.

Dr 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.

An immediate application of the technology may be as a stretchable, on-demand treatment for burns or other skin conditions, said Hyunwoo Yuk, a graduate student at MIT.

“It’s a very versatile matrix,” Yuk said. “The unique capability here is, when a sensor senses something different, like an abnormal increase in temperature, the device can, on demand, release drugs to that specific location and select a specific drug from one of the reservoirs, which can diffuse in the hydrogel matrix for sustained release over time.”

Delving deeper, Dr Zhao envisions hydrogel to be an ideal, biocompatible vehicle for delivering electronics inside the body. He is currently exploring hydrogel’s potential as a carrier for glucose sensors as well as neural probes.

Sheet of hydrogel bonded to

a matrix of polymer islands

(red) that can encapsulate

electronic components

Photo by Melanie Gonick/MIT

Engineers say they have designed “smart wound dressing,” 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 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, PhD, of the Massachusetts Institute of Technology in Cambridge.

The hydrogel, which was describe in Nature Materials last month, 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 paper published in Advanced Materials, Dr Zhao and his colleagues described embedding various electronics within the hydrogel, such as conductive wires, semiconductor chips, LED lights, and temperature sensors.

Dr Zhao said 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,” Dr Zhao said. “These two systems have drastically different properties. If you want to put electronics in close contact with the human body for applications such as healthcare 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.

“They’re often used as degradable biomaterials at the current stage,” Dr Zhao said. “If you want to make an electronic device out of hydrogels, you need to think of long-term stability of the hydrogels and interfaces.”

To get around these challenges, his team 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. The researchers also devised a method to strongly bond the hydrogel to various nonporous surfaces.

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.

Dr 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.

An immediate application of the technology may be as a stretchable, on-demand treatment for burns or other skin conditions, said Hyunwoo Yuk, a graduate student at MIT.

“It’s a very versatile matrix,” Yuk said. “The unique capability here is, when a sensor senses something different, like an abnormal increase in temperature, the device can, on demand, release drugs to that specific location and select a specific drug from one of the reservoirs, which can diffuse in the hydrogel matrix for sustained release over time.”

Delving deeper, Dr Zhao envisions hydrogel to be an ideal, biocompatible vehicle for delivering electronics inside the body. He is currently exploring hydrogel’s potential as a carrier for glucose sensors as well as neural probes.

Sheet of hydrogel bonded to

a matrix of polymer islands

(red) that can encapsulate

electronic components

Photo by Melanie Gonick/MIT

Engineers say they have designed “smart wound dressing,” 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 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, PhD, of the Massachusetts Institute of Technology in Cambridge.

The hydrogel, which was describe in Nature Materials last month, 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 paper published in Advanced Materials, Dr Zhao and his colleagues described embedding various electronics within the hydrogel, such as conductive wires, semiconductor chips, LED lights, and temperature sensors.

Dr Zhao said 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,” Dr Zhao said. “These two systems have drastically different properties. If you want to put electronics in close contact with the human body for applications such as healthcare 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.

“They’re often used as degradable biomaterials at the current stage,” Dr Zhao said. “If you want to make an electronic device out of hydrogels, you need to think of long-term stability of the hydrogels and interfaces.”

To get around these challenges, his team 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. The researchers also devised a method to strongly bond the hydrogel to various nonporous surfaces.

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.

Dr 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.

An immediate application of the technology may be as a stretchable, on-demand treatment for burns or other skin conditions, said Hyunwoo Yuk, a graduate student at MIT.

“It’s a very versatile matrix,” Yuk said. “The unique capability here is, when a sensor senses something different, like an abnormal increase in temperature, the device can, on demand, release drugs to that specific location and select a specific drug from one of the reservoirs, which can diffuse in the hydrogel matrix for sustained release over time.”

Delving deeper, Dr Zhao envisions hydrogel to be an ideal, biocompatible vehicle for delivering electronics inside the body. He is currently exploring hydrogel’s potential as a carrier for glucose sensors as well as neural probes.