PDMS
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Attachable Skin Monitors that Wick the Sweat Away
- A silicone membrane for wearable devices is more comfortable and breathable thanks to better-sized pores made with the help of citric acid crystals. -
A new preparation technique fabricates thin, silicone-based patches that rapidly wick water away from the skin. The technique could reduce the redness and itching caused by wearable biosensors that trap sweat beneath them. The technique was developed by bioengineer and professor Young-Ho Cho and his colleagues at KAIST and reported in the journal Scientific Reports last month.
“Wearable bioelectronics are becoming more attractive for the day-to-day monitoring of biological compounds found in sweat, like hormones or glucose, as well as body temperature, heart rate, and energy expenditure,” Professor Cho explained. “But currently available materials can cause skin irritation, so scientists are looking for ways to improve them,” he added.
Attachable biosensors often use a silicone-based compound called polydimethylsiloxane (PDMS), as it has a relatively high water vapour transmission rate compared to other materials. Still, this rate is only two-thirds that of skin’s water evaporation rate, meaning sweat still gets trapped underneath it.
Current fabrication approaches mix PDMS with beads or solutes, such as sugars or salts, and then remove them to leave pores in their place. Another technique uses gas to form pores in the material. Each technique has its disadvantages, from being expensive and complex to leaving pores of different sizes.
A team of researchers led by Professor Cho from the KAIST Department of Bio and Brain Engineering was able to form small, uniform pores by crystallizing citric acid in PDMS and then removing the crystals using ethanol. The approach is significantly cheaper than using beads, and leads to 93.2% smaller and 425% more uniformly-sized pores compared to using sugar. Importantly, the membrane transmits water vapour 2.2 times faster than human skin.
The team tested their membrane on human skin for seven days and found that it caused only minor redness and no itching, whereas a non-porous PDMS membrane did.
Professor Cho said, “Our method could be used to fabricate porous PDMS membranes for skin-attachable devices used for daily monitoring of physiological signals.”
“We next plan to modify our membrane so it can be more readily attached to and removed from skin,” he added.
This work was supported by the Ministry of Trade, Industry and Energy (MOTIE) of Korea under the Alchemist Project.
Image description:
Smaller, more uniformly-sized pores are made in the PDMS membrane by mixing PDMS, toluene, citric acid, and ethanol. Toluene dilutes PDMS so it can easily mix with the other two constituents. Toluene and ethanol are then evaporated, which causes the citric acid to crystallize within the PDMS material. The mixture is placed in a mould where it solidifies into a thin film. The crystals are then removed using ethanol, leaving pores in their place.
Image credit:
Professor Young-Ho Cho, KAIST
Image usage restrictions:
News organizations may use or redistribute this image, with proper attribution, as part of news coverage of this paper only.
Publication:
Yoon, S, et al. (2021) Wearable porous PDMS layer of high moisture permeability for skin trouble reduction. Scientific Reports 11, Article No. 938. Available online at https://doi.org/10.1038/s41598-020-78580-z
Profile:
Young-Ho Cho, Ph.D
Professor
mems@kaist.ac.kr
https://mems.kaist.ac.kr
NanoSentuating Systems Laboratory
Department of Bio and Brain Engineering
https://kaist.ac.kr
Korea Advanced Institute of Science and Technology (KAIST)
Daejeon, Republic of Korea
(END)
2021.02.22 View 10884 -
Firefly inspired high efficiency LED technology developed
A firefly inspired, high efficiency self-illuminating LED has been developed.
Professor Jeong Gi Hoon (Department of Bio and Brain Engineering) mimicked the nanostructure of the external layer of the illumination organ of a firefly and succeeded in fabricating high illumination efficiency LED lenses.
Conventional lenses required expensive anti-reflection coating. The developed lenses utilize the bio-inspired nanostructure on the surface of the lenses themselves to reduce the reflectivity of the lenses thereby decreasing production costs.
The developed antireflection nanostructure is expected to be applied to various digital devices and lighting fixtures.
Antireflective structures have been applied in various fields in order to enhance light efficiency However these structures have been limited to flat surfaces and therefore was difficult to implement to curved surfaces like LED lenses.
Professor Jeong’s team solved this problem by using three dimensional micro molding processes.
The team fabricated the nanostructure by forming a single nanoparticle layer on the silicon oxide and performing dry etching. On this nanostructure PDMS was poured and manipulated to fabricate a lens structure similar to that of a firefly.
The fabricated lens showed similar efficiency as conventional antireflection coating.
2012.11.29 View 7855 -
Gold prize for Sungkoo Yeo and silver prize for Youngsik Kim at 'Samsung Electrics paper contest'
Gold prize for Sungkoo Yeo and silver prize for Youngsik Kim at ‘Samsung Electrics paper contest’
Sungkoo Yeo, doctorate student at the division of Electrical Engineering, and Youngsik Kim, doctorate students at the division of Mechanical Engineering, won gold and silver prizes respectively at ‘the 2nd Inside edge paper contest’ organized by Samsung Electronics.
Yeo, under the supervisory of Professor Youngse Kwon, won the glory of gold prize in recognition of his highly evaluated researches in the fields of silicon-based micro mold manufacturing technologies and fine shaping technologies revealed by his paper of ‘"Fabrication of Microlens array Using PDMS Replica Molding and Oxidized Porous Silicon Bulk Micromachining’.
Kim, under the supervisory of Professor Seungwoo Kim, also won the silver prize for his research performances over the thickness pattern measuring technologies of transparent thin film coated on the pattern of an opaque metal in the field of optical technology unveiled by his paper of "Dispersive white-light interferometry for in-line inspection of thin-film layers on patterned structures".
Inside Edge paper contest is an academic paper contest organized by Samsung Electronics to reveal the fresh ideas and potential technologies of the young talented.
2006.11.27 View 15202