Tag Archives: #sweat

Novel Film That Evaporates Sweat Six Times Faster and Holds 15 Times More Moisture (Material Science)

Promising applications include underarm pads, insoles and shoe linings; Moisture harvested could power small wearable electronics.

A team of researchers from the National University of Singapore (NUS) has created a novel film that is very effective in evaporating sweat from our skin to keep us cool and comfortable when we exercise, and the moisture harvested from human sweat can be used to power wearable electronic devices such as watches, fitness trackers, and more.

An NUS research team led by Assistant Professor Tan Swee Ching (seated, left) and Professor Ding Jun (seated right) has developed a novel film that is extremely effective in evaporating sweat from our skin. Promising applications include shoe insoles and linings, as well as underarm pads for sweat absorption. © National University of Singapore

Sweating is a natural process for our body to reduce thermal stress. “Sweat is mostly composed of water. When water is evaporated from the skin surface, it lowers the skin temperature and we feel cooler. In our new invention, we created a novel film that is extremely effective in evaporating sweat from our skin and then absorbing the moisture from sweat. We also take this one step further – by converting the moisture from sweat into energy that could be used to power small wearable devices,” explained research team leader Assistant Professor Tan Swee Ching, who is from the NUS Department of Material Science and Engineering.

The main components of the novel thin film are two hygroscopic chemicals – cobalt chloride and ethanolamine. Besides being extremely moisture-absorbent, this film can rapidly release water when exposed to sunlight, and it can be ‘regenerated’ and reused for more than 100 times.

To make full use of the absorbed sweat, the NUS team has also designed a wearable energy harvesting device comprising eight electrochemical cells (ECs), using the novel film as the electrolyte. Each EC can generate about 0.57 volts of electricity upon absorbing moisture. The overall energy harvested by the device is sufficient to power a light-emitting diode. This proof-of-concept demonstration illustrates the potential of battery-less wearables powered using human sweat.

This technological breakthrough was reported in the September print issue of the scientific journal Nano Energy.

Absorbing moisture for personal comfort

Conventional hygroscopic materials such as zeolites and silica gels have low water uptake and bulk solid structures, making them unsuitable for absorbing moisture from sweat evaporation. In comparison, the new moisture-absorbing film developed by NUS researchers takes in 15 times more moisture and do this 6 times faster than conventional materials.

A team of researchers from the National University of Singapore invented a novel thin film that evaporates sweat six times faster and holds 15 times more moisture than conventional materials. In this prototype, the insole coated with the novel thin film turns from blue to pink as it absorbs moisture. The insole can be easily ‘regenerated’ by putting it under the sun, and be reused for more than 100 times. © National University of Singapore

In addition, this innovative film shows a colour change upon absorbing moisture, from blue to purple, and finally pink. This feature can be used an indicator of the degree of moisture absorption.

The NUS team packaged the film into breathable and waterproof polytetrafluoroethylene (PTFE) membranes, which are flexible and commonly used in clothing, and successfully demonstrated the application of the moisture-absorption film for underarm pad, shoe lining and shoe insole.

Asst Prof Tan said, “Underarm sweating is embarrassing and frustrating, and this condition contributes to the growth of bacteria and leads to unpleasant body odour. Accumulation of perspiration in the shoes could give rise to health problems such as blisters, calluses, and fungal infections. Using the underarm pad, shoe lining and shoe insole embedded with the moisture-absorbing film, the moisture from sweat evaporation is rapidly taken in, preventing an accumulation of sweat and provides a dry and cool microclimate for personal comfort.”

“The prototype for the shoe insole was created using 3D printing. The material used is a mixture of soft polymer and hard polymer, thus providing sufficient support and shock absorption,” explained research team co-leader Professor Ding Jun, who is also from the NUS Department of Material Science and Engineering.

The NUS team now hopes to work with companies to incorporate the novel moisture-absorption film into consumer products.

Reference: Xueping Zhang, Jiachen Yang, Ramadan Borayek, Hao Qu, Dilip Krishna Nandakumar, Qian Zhang, Jun Ding, Swee Ching Tan, “Super-hygroscopic film for wearables with dual functions of expediting sweat evaporation and energy harvesting”, Nano Energy, Volume 75, 2020, 104873, ISSN 2211-2855,
https://doi.org/10.1016/j.nanoen.2020.104873.
(http://www.sciencedirect.com/science/article/pii/S2211285520304304)

Provided by National University of Singapore

No Stain? No Sweat: Terahertz Waves Can Image Early-stage Breast Cancer Without Staining (Medicine)

A team of researchers at Osaka University, in collaboration with the University of Bordeaux and the Bergonié Institute in France, has succeeded in terahertz imaging of early-stage breast cancer less than 0.5 mm without staining, which is difficult to identify even by pathological diagnosis. Their work provides a breakthrough towards rapid and precise on-site diagnosis of various types of cancer and accelerates the development of innovative terahertz diagnostic devices.

A schematic drawing of the measurement of breast cancer tissue fabricated on a nonlinear optical crystal. ©Osaka University

Breast cancer is roughly divided into two types: invasive and non-invasive. The former, invasive ductal carcinoma (IDC), begins in the cells of a breast duct, growing through the duct walls and into the surrounding breast tissue, potentially spreading to other parts of the body. The latter, ductal carcinoma in situ (DCIS), is an early-stage small breast cancer confined to the breast duct, but it can lead to invasive cancer. Therefore, early detection of DCIS is crucial.

For pathological diagnosis of cancer, the tissue sample is chemically stained, and a pathologist makes a diagnosis using an image of the stained tissue. However, the staining process takes time, and it is difficult to distinguish DCIS from malignant IDC as they look nearly identical.

Terahertz imaging can distinguish cancer tissue from normal tissue without staining and radiation exposure. However, it was still difficult to identify an individual DCIS lesion (which typically range from 50 to 500 μm) by terahertz imaging due to its diffraction-limited spatial resolution of just several millimeters.

A terahertz image of unstained tissue (top) compared with the same tissue after staining with H&E (bottom). In the stained image, the ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) compartments are highlighted by red and blue dotted lines, respectively. ©Osaka University.

“To overcome this drawback, we developed a unique imaging technique in which terahertz light sources that are locally generated at irradiation spots of laser beams in a nonlinear optical crystal directly interact with a breast cancer tissue sample. Consequently, we succeeded in clearly visualizing a DCIS lesion of less than 0.5 mm,” explains lead author Kosuke Okada. The accuracy of this technique is approximately 1000 times higher than that of conventional techniques using terahertz waves.

The researchers also found that terahertz intensity distributions were different between DCIS and IDC, suggesting the possibility of quantitative determination of cancer malignancy.

The breast cancer tissue sample was provided and histologically assessed by collaborators from the University of Bordeaux and the Bergonié Institute. “One of the challenges in this research is preparing a high-quality breast cancer tissue sample fabricated on a nonlinear optical crystal. It is one of the great achievements of international joint research,” says corresponding author Masayoshi Tonouchi.

“Combining our technique with machine learning will aid in the early detection of cancer and determination of cancer malignancy, as well as development of innovative terahertz diagnostic devices using Micro Electro Mechanical Systems.”

Provided by Osaka University

Drinking Hot Drinks Can Cool You Down (Biology)

There’s nothing quite like a long run on a sweltering summer day to make you thirst for a big ole’ mug of hot tea. Huh? Believe it or not, research has found that (under the right conditions) a hot drink after exercise can actually cool you down better than a cold one.

It sounds like something Snopes would shoot down. How could chugging some chai post-run possibly cool your body? There’s scientific evidence, we promise.

In a 2012 study, Dr. Ollie Jay from the University of Sydney examined the effectiveness of drinking both hot and cold drinks when it comes to lowering the amount of heat stored by your body. Volunteers were asked to ride bikes for 75 minutes at 75 degrees Fahrenheit (24 degrees Celsius) with 23 percent relative humidity — the equivalent of a nice summer day. Five minutes before the workout and every 15 minutes after, they drank water at one of four different temperatures: 34 degrees, 50 degrees, 98.6 degrees, or 122 degrees Fahrenheit (1.5 degrees, 10 degrees, 37 degrees, or 50 degrees Celsius).

The results? Those who drank the hottest drinks ended up cooling down the most. How is that possible? It has to do with your sweat and how it’s influenced by drink temperature. Sweat (or, more importantly — the evaporation of sweat) is key for helping your body come back to a temperature baseline. When you drink a hot drink, your body bumps up its sweat production, leading to more cooling. You might think that wouldn’t be enough to counteract the hot drink, but the sweat output actually outweighs any internal heating.

But here’s the slight catch — this study was performed under conditions where the volunteers’ sweat was able to evaporate completely. If you were to try the hot drink trick somewhere with poor airflow and/or high humidity, the results would likely be much different (i.e., cold drinks would probably win out). Would you ever reach for a post-workout hot chai?

Sweat Is Not Detoxifying (Biology)

Doesn’t it feel good to sweat? To feel your muscles warm up, to feel your heart pump, to feel the toxins escape through your pores … well, everything except that last part. It turns out that, contrary to popular belief, sweat really isn’t detoxifying. The real detox happens in completely different organs. Still, we love to sweat all the same.

Saunas, hot yoga studios, and sweat lodges all swear by the detoxifying effects of sweating. And it seems reasonable: Something smelly is coming out of your pores, which means there’s less smelly stuff inside of you. Right?

In truth, hardly any harmful chemicals come out in your sweat. Sweat is mostly water, plus a certain concentration of sodium, chloride, and potassium, and sometimes proteins and fatty acids. It does include some “toxins,” but only trace amounts, and those are dwarfed by the quantities that your liver and kidneys constantly flush out of your body.

“Most of the ‘toxins’ that concern people include pesticides, residue from plastics, or from air pollution,” dermatologist Tsippora Shainhouse told Vice. “These tend to be fat-soluble, and do not dissolve well in water, so they will not be removed from the body in any significant quantity, given that sweat is 99 percent water.”

But what about the smell? The stink of sweat isn’t from toxins, but from the chemistry of your own skin. You have two types of sweat glands: eccrine glands and apocrine glands. Eccrine glands are located all over your body, and the sweat they produce is there to cool you down when you’re hot. That sweat is usually odorless, but it can take on a funky smell when it’s broken down by bacteria on your skin or if you’ve been eating particularly pungent foods like garlic or cabbage. Sweating after a night of drinking can also douse your eccrine-gland sweat with diacetic acid, which smells like vinegar — though again, you’re just sweating out the smell, not the alcohol or any other “toxins.”

Your apocrine glands lead to even funkier sweat. These glands are located in the spots known for stinky smells, like the groin and armpits, and they’re responsible for the telltale scent of stress sweat. The sweat they produce is milky and odorless until, again, the bacteria on your skin start chowing down and producing a bouquet of B.O.

To reiterate: Both types of sweat start out odorless, for the most part. They only get smelly when they interact with the bacteria on your skin, and any smell they do start out with is due to compounds your body has already broken down and was getting rid of anyway. Sweat is almost entirely water, and that water contains hardly anything you could consider a toxin.

On the contrary, attempting to “detox” by sweating it out can actually do more harm than good. If you don’t replace that sweat by drinking enough water, you’ll get dehydrated, which is the perfect way to stress your kidneys and keep them from doing their job — you know, the job of detoxifying you. That’s not to say sweating is bad. It’s a great way to cool off, as long as you follow it up with a refreshing swig of water.


Yellow Pit Stains Aren’t Solely Caused By Sweat (Chemistry / Science)

Ugh, sweat. Alongside excess body hair and a stubborn need to store energy as fat, sweating is one of the many annoying ways your body works to ensure your survival. (It means well, we’re sure). It may surprise you to learn, however, that when it comes to the yellow pit stains on your favorite white cotton tee, sweat’s not to blame. Not sweat alone, anyway.

The true culprit behind yellow underarm stains is a chemical reaction among the proteins in your sweat, the cotton in your shirt, and the aluminum salts in your antiperspirant or deodorant. Yes, the very thing you use to keep yourself looking and smelling fresh is the reason your white undershirts start looking so gnarly after a few dozen wears. You can also blame that disgusting chemistry for the stiff texture that comes with those stains.

In fact, because aluminum-based deodorants are a relatively recent phenomenon, pit stains haven’t always been yellow. Around the turn of the 20th century, one of the most popular antiperspirants was a product called Odorono. Despite containing aluminum, the substance itself was red in color, and that led to red underarm stains. When it comes to clothing artifacts from history, textile conservators run into sweat stains that are yellow, orange, red, brown, and even green. Fun fact: Astronaut sweat has even corroded the metal components in the spacesuits of history. (If even astronauts deal with armpit sweat, maybe we don’t feel so bad about ourselves).

Unfortunately, to prevent pit stains, the first thing most people resort to is just using more antiperspirant. That’s obviously the wrong choice, as we’ve explained above. You could try switching to a non-antiperspirant deodorant that doesn’t contain aluminum salts, although that may just end up trading big yellow marks for big wet marks.

The best solution is probably to tackle pit stains right after you’ve worn the shirt. For new, un-yellowed garments, try pre-treating with an enzymatic laundry spray directly after you wear it (keep the spray by the laundry hamper to make things easier on yourself). If your antiperspirant has already done its damage, soak the shirt in vinegar, hydrogen peroxide, or an oxygenated bleach like OxiClean to try to get the yellow out. Important, though, is to never use chlorine bleach, which actually yellows in the presence of proteins like those found in your sweat.


References: (1) http://www.esquire.com/style/advice/a45088/how-to-get-rid-of-pit-stains-once-and-for-all/ (2) http://cenblog.org/artful-science/2012/02/27/sweat-stained-artifacts/ (3) https://www.nytimes.com/2014/03/02/magazine/who-made-that-antiperspirant.html?_r=0 (4) http://pubsapp.acs.org/cen/science/89/8919sci1.html (5) https://www.esquire.com/style/advice/a45088/how-to-get-rid-of-pit-stains-once-and-for-all/ (6) https://www.dollarshaveclub.com/content/story/heres-get-pit-stains-get-rid