– The silicone membrane for wearables is more comfortable and breathable thanks to the better size pores made with the help of citric acid crystals. –
New preparation technology creates thin silicone patches that quickly absorb water away from the skin. This technology can reduce the redness and itching caused by the wearable biosensors that trap sweat underneath. The technology was developed by Bioengineer, Professor Yong Ho Chu and colleagues at KAIST and published in the journal. Scientific Reports Last month.
Professor Chu explained: “Wearable bionics is becoming more attractive for daily monitoring of biological compounds in sweat, such as hormones or glucose, as well as body temperature, heart rate and energy expenditure.” He added: “But the materials currently available can cause skin irritation, so scientists are looking for ways to improve them.”
Attachment biosensors often use a silicon-based compound called polymethylsiloxane (PDMS), since the water vapor transfer rate is relatively high compared to other materials. However, this rate is only two-thirds the rate at which water evaporates in the skin, which means that sweat is still trapped underneath.
Current manufacturing methods mix PDMS with beads or dissolved materials, such as sugars or salts, and then remove them to leave the pores in place. Another technique uses gas to form pores in the material. Each technique has its drawbacks, from being expensive and complicated to leaving pores of different sizes.
A team of researchers led by Professor Chu of the Department of Bioengineering and Brain KAIST was able to create small, uniform pores by crystallizing citric acid in PDMS and then removing the crystals with ethanol. This approach is much cheaper than using beads, and results in 93.2% smaller pores and 425% more uniform pores compared to using sugar. Most importantly, the membrane conveys water vapor 2.2 times faster than human skin.
The team tested their membrane on human skin for seven days and found that it only causes slight redness and is not itchy, while PDMS causes the non-porous membrane.
“Our method can be used to manufacture porous PDMS films for skin-binding devices used for daily monitoring of physiological signals,” said Professor Chu.
He added, “We then plan to modify our membrane so that it can be attached easily and removed from the skin.”
This work was supported by the Korea Ministry of Trade, Industry and Energy (MOTIE) under the Alchemist Project.
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