Even while working out, sweat-proof electronic “Smart Skin” Accurately Measures Vitals

A sweat-proof electronic skin has been created by MIT researchers in South Korea. It is a conformable, sticky patch with embedded sensors that can track a person’s health without breaking down or coming off even when the wearer is perspiring.

The patch is made of synthetic sweat ducts that the researchers engraved through the material’s ultrathin layers to create pores similar to those found in human skin. Similar to the Japanese paper-cutting craft, kirigami, the pores pierce the patch in a pattern. The idea makes sure that perspiration can evaporate through the patch, preventing irritation of the skin and harm to the installed sensors.

Additionally, the kirigami design helps the patch conform to human flesh as it stretches and flexes. This flexibility, along with the material’s resistance to perspiration, enables it to monitor a person’s health over prolonged periods, which was not possible with earlier “e-skin” concepts. The findings, which were published on June 30, 2021, in Science Advances, represent a step forward toward durable smart skins that could monitor daily vitals or the development of skin cancer and other conditions.

According to Jeehwan Kim, an assistant professor of mechanical engineering at MIT, there won’t be any sweat accumulation, inaccurate data, or skin detachment with this new, conformable, and breathable skin patch. Jeehwan Kim goes on to state that his group can provide wearable sensors that are capable of long-term continuous tracking.

Hanwool Yeon, the primary writer and an MIT postdoc, in addition to researchers in the MIT departments of mechanical engineering, materials science and engineering, and the research laboratory of electronics, as well as associates from the South Korean cosmetics giant Amorepacific and other research institutions, are among Kim’s co-authors.

Overcoming a sweaty problem

The goal of Kim’s team is to create bendable semiconductor layers. The scientists invented a process known as remote epitaxy, which entails growing ultrathin, premium semiconductor films on wafers at high temps and then picking out particular films with care. After that, the films can be stacked and combined to produce sensors that are much thinner and more flexible than conventional wafer-based concepts.

Their efforts recently caught the attention of the cosmetics company Amorepacific, which was interested in creating thin wearable tape to gradually monitor changes in the epidermis. The business and Kim worked together to transform the group’s flexible semiconducting films into something that could be used for a long time.

sweating, on the other hand, proved to be a challenge that other e-skin ideas have yet to overcome. Most experimental ideas incorporate sensors into goods made of sticky, non-breathable polymers. Different patterns constructed of woven nanofibers can let air through but not sweat. Kim knew that in order for an e-skin to operate for an extended period of time, it would need to be permeable to both sweat and condensate

According to Kim, sweat can accumulate within the user’s epidermis and the e-skin, potentially causing both skin damage and sensor problems. Kim says that by allowing sweat to pass through electronic skin, he and his collaborators tried to address these two issues concurrently.

A porous solution

The researchers glanced at human sweat pores for design inspiration. They found that pores are randomly distributed throughout the epidermis and have an average diameter of about 100 microns. They performed some early simulations to figure out how they could overlay and arrange synthetic pores in a way that wouldn’t obstruct real pores within the human epidermis.

Yeon mentioned that the group’s simple concept is to create highly permeable pathways for the perspiration while also supplying synthetic sweat ducts in electronic skin. The group may achieve more durable heat up in this manner as well.

They initially had a regular arrangement of pores, each roughly the size of a sweat pore. They found that the entire pattern could effectively permeate sweat if pores were arranged closely together, at a distance smaller than the average pore’s circumference. However, they also found that if a thin film were used to engrave this fundamental opening design, the film was not extremely flexible and readily broke when applied to the skin.

By developing a pattern of replicating dumbbells as opposed to basic openings that relaxed strain rather than focusing it in one area, the scientists discovered they could improve the strength and flexibility of the hole pattern. This design, when reproduced into a material, produced an elastic, kirigami-like effect.

Kim explains this by stating that while a piece of paper wrapped around a ball is not conformable, it might if the kirigami pattern was reduced in the paper. Kim proceeds by saying that his group came up with the concept of joining the holes with a cut to give the skin a kirigami-like conformability. Rendering it possible for sweat to penetrate while doing so.

In accordance with this hypothesis, the team created an electronic epidermis out of several functional layers, each of which they engraved with pores that were shaped like dumbbells. Ultrathin semiconductor-patterned sensors embedded in the layers of the epidermis measure temperature, moisture, ultraviolet exposure, mechanical strain, and other factors. This sensor array is encased between two thin protective sheets, which are themselves coated in an adhesive polymer.

Yeon notes that the e-skin is similar to human skin in that it is highly pliable, soft, and permeable to sweat.

The e-skin was attached to a volunteer’s wrist and forehead as the scientists inspected it. The volunteer constantly used the tape for more than a week. His temperature, hydration, UV exposure, and pulse were accurately measured throughout the procedure by the new e-skin, even when he was performing sweat-inducing activities like jogging on a treadmill for 30 minutes and eating a spicy meal.

In contrast to other e-skin designs that lacked sweat permeability and rapidly separated from the skin, the team’s creation adhered to the volunteer’s forehead as he was requested to frown repeatedly while perspiring profusely.

Kim wants to make the construction more durable and tough. The kirigami design on the tape makes it very conformable and sweat-permeable, but it also makes it fairly vulnerable to friction due to the tape’s ultrathin form and this pattern. Volunteers were therefore required to wrap a covering around the tape to protect it while performing tasks like taking a shower.

Yeon claimed that because the e-skin is so delicate, bodily harm could be done to it. Yeon also mentioned that he and his group want to make artificial epidermis more resilient.

Originally published by: scitechdaily.com, July 18, 2021.

Reference: “Long-term reliable physical health monitoring by sweat pore–inspired perforated electronic skins” by Hanwool Yeon, Haneol Lee, Yeongin Kim, Doyoon Lee, Youngjoo Lee, Jong-Sung Lee, Jiho Shin, Chanyeol Choi, Ji-Hoon Kang, Jun Min Suh, Hyunseok Kim, Hyun S. Kum, Jaeyong Lee, Daeyeon Kim, Kyul Ko, Boo Soo Ma, Peng Lin, Sangwook Han, Sungkyu Kim, Sang-Hoon Bae, Taek-Soo Kim, Min-Chul Park, Young-Chang Joo, Eunjoo Kim, Jiyeon Han and Jeehwan Kim, 30 June 2021, Science.
DOI: 10.1126/sciadv.abg8459