Wearable Sensor to Analyze Human Sweat

 More sensory input into healthcare. 

Wearable Sensor Detects Even More Compounds in Human Sweat

By Caltech News,   August 23, 2022

A wearable sensor developed by researchers at the California Institute of Technology can detect amino acids and certain vitamins in small amounts of human sweat.

The technology features molecularly imprinted polymers that act as reusable antibodies, overcoming the challenges associated with previous sweat sensors that use antibodies (which can be used just once) to detect compounds at low concentrations.

For a sensor to detect the amino acid glutamine, for instance, the polymer would be prepared with glutamine molecules, leaving holes shaped like glutamine when the molecules are removed through a chemical process.

An electrical signal is generated when sweat contacts the inner layer of the sensor, and the signal weakens as glutamine molecules are plugged into the holes in the polymer, helping to determine how much glutamine is in the wearer's sweat.

The use of microfluidics also means the sensor can operate with a miniscule amount of sweat. ... 

Thanks to microfluidics and the use of a different type of drug, the sensor now needs less sweat, and the current needed to generate the sweat can be very small. .... '

Caltech Article   

Sweat Powering Wearables

Have heard this being proposed from time to time over the years,  but it never happened.   The power involved was always too low and the electricity too cheap.     Good to know it is still possible for particular on-demand applications.  Some intriguing details here.

Why Sweat Will Power Your Next Wearable
Biofuel cells can generate enough watts for fitness trackers and health monitors  By Patrick Mercier and Joseph Wang in IEEE Spectrum

Admit it—you love your smart watch and all the amazing things you can do with it. But the task of keeping it charged can be annoying. A longer battery life would be great—but with batteries, the amount of energy stored correlates with volume, and bigger batteries add bulk and weight. All wearables, including fitness trackers, audio-enhancing hearables that go in your ear, and augmented-reality contact lenses, have a similar power problem. And today’s batteries are too bulky and stiff for use in wearables that are woven into textiles or directly mounted on a user’s skin.

The power demands for these kinds of devices range from 1 milliwatt for a basic step counter to tens of milliwatts for more advanced smart watches. When using small, centimeter-size batteries, which have capacities on the order of 10 to 300 milliampere hours, this results in battery lifetimes of only a few days at most.

Some researchers are tackling the wearable power challenge by developing new types of stretchable batteries and supercapacitors. However, it’s hard to produce such batteries using screen printing, a process that dramatically lowers costs. Other developers are trying to bypass batteries altogether by using Near Field Communication chipsets for wireless power transmission. But NFC technology requires you to have an external power source, like a mobile phone, within a few centimeters of the wearable; once you move the phone away, the wearable stops working.  ... "

Sweat and Electronic Skin

More sensor examples and sources of data for monitoring and analysis.

Electronic Skin Powered by Sweat Can Monitor Health, Serve as Human-Machine Interface
Caltech News

By Emily Velasco
April 22, 2020

California Institute of Technology (Caltech)'s Wei Gao has developed a perspiration-powered electronic skin (e-skin) that can be applied directly to human skin, with embedded sensors to monitor the wearer’s vital signs. The e-skin's built-in biofuel cells absorb lactate from the wearer's sweat, which combines with air to generate water, pyruvate, and electricity, powering the sensors and a Bluetooth device. This enables the e-skin to wirelessly broadcast sensor readings, and the biofuel cells can produce continuous, stable power output over multiple days. Gao said the goal is to create diverse sensors that can be embedded in the e-skin for multiple functions. He said, "This can be a human–machine interface. The vital signs and molecular information collected using this platform could be used to design and optimize next-generation prosthetics."

Wearable Sweat Sensors

Recall some research using sweat as a means of diagnosing.

Wearable sensors detect what's in your sweat
by Kara Manke, University of California - Berkeley

Needle pricks not your thing? A team of scientists at the University of California, Berkeley, is developing wearable skin sensors that can detect what's in your sweat.

They hope that one day, monitoring perspiration could bypass the need for more invasive procedures like blood draws, and provide real-time updates on health problems such as dehydration or fatigue.

In a paper appearing today in Science Advances, the team describes a new sensor design that can be rapidly manufactured using a "roll-to-roll" processing technique that essentially prints the sensors onto a sheet of plastic like words on a newspaper.

They used the sensors to monitor the sweat rate, and the electrolytes and metabolites in sweat, from volunteers who were exercising, and others who were experiencing chemically induced perspiration.

"The goal of the project is not just to make the sensors but start to do many subject studies and see what sweat tells us—I always say 'decoding' sweat composition," said Ali Javey, a professor of electrical engineering and computer science at UC Berkeley and senior author on the paper.

"For that we need sensors that are reliable, reproducible, and that we can fabricate to scale so that we can put multiple sensors in different spots of the body and put them on many subjects," said Javey, who also serves as a faculty scientist at Lawrence Berkeley National Laboratory. .....  "