Move Over Fitness Bands; Biomedical Tattoos and Patch-like Wearables Are Here.

“The ability to capture, with research level precision, tailored data outside of a clinic…that’s the Holy Grail,”

-Dr. Alvaro Pascual-Leone, Associate Dean of Harvard Medical School.

Remember your last medical check up? Waiting in the queue for your turn, and then spending around twenty minutes with the doctor. So, to save yourself from the trouble you bought your first fitness band, that helped you track your blood pressure, hearth rate etc with the help of a smart phone app using bluetooth, and you felt like this was the best you could get. But, hold on. We now have a new generation of wearables hitting the market soon. These wearables are like patches that are so soft that they actually align to the shape of your skin and monitor your health. Life just got a bit easier!

So how do these patch-like wearables actually work ? Well, they are made using organic semiconductors and carbon nanotubes. And, what makes them so more impressive other than their accuracy is that they are just the size of a british pence and just some tens of micrometers thick. More like a temporary tattoo worn by children. These are so thin, that once they are worn/sticked they are practically impossible to feel.First, let’s get an idea how they are manufactured. The process starts with arranging the electrical components ( transistors, capacitors, resistors , diodes) on a normal semiconductor substrate like silicon or germanium arsenide. The whole package is like a sandwich, with a sacrificial layer (silicon dioxide in case of silicon) between the semiconductor. Next a chemical solution dissolves the sacrificial layer and the components on the top layer are transferred to a stamp made of silicone using raised areas on the stamp. After picking up the devices, the silicone stamp deposits them onto a temporary substrate, usually a plastic-coated glass plate. This plate then goes through a standard photolithography process that connects the devices with copper conductors in the form of serpentine coils, which make the connections stretchable. The final step involves the circuit to be worn by an individual, supported by a rubber sheet on the plate , through the adhesive already present.

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The BioStamps, packed with style and science.

One of the first ideas for skin-like devices was  proposed by John Rogers,a materials science professor at the University of Illinois with a bold vision: Someday, he believes, we will all have sensors on our bodies that send information to a mobile phone, similar to the way a car’s sensors feed the vehicle’s computer. He, along with Roozbeh Ghaffari started a company called MC10, in Cambridge, Mass. One of the major components of this $60 million dollar company, is the BioStamp. Right now they are availiable only for research, nevertheless it has managed to attract the attention of many multinational corporations, Government agencies, and independent doctors and fitness advisors.

“We’re basically taking this new technology  and creating an unprecedented understanding and engagement for people around their health.”

-Dr. Leslie Saxon

BioStamp is powered by  harvesting energy from near-field communication (NFC) radio signals, typically from the wearer’s cellphone. It communicates with the phone the same way. NFC, which sends data at 13.56 megahertz, is a feature of almost all current-model smartphones, which use it for wireless-payment schemes. . A Biostamp can contain hundreds of thousands of transistors, as well as resistors, LEDs, and a radio-frequency antenna. It’s waterproof and breathable, and it costs just tens of cents when manufactured in quantity. It can be worn for a week or so, before the normal shedding of skin cells begins to force the thin substrate to peel from the skin, like an early season sunburn. A stretchable resin helps make it waterproof. In some BioStamp stickers due to the absence of a microprocessor the data is analysed by a smart phone app whereas in other cases the unit comes with its own microprocessor that directly sends the result to the database.

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The Three Main BioStamps

This technology is becoming advanced day by day. The BioStamp can be used to monitor your blood pressure, the chemical composition of your sweat, or your UV exposure and temperature. To measure the blood pressure, it might use piezoelectricity sensors, that estimate the blood pressure through the electricity formed by the pressure exerted on the device by the blood vessels under the skin. Another process involves measuring the pulse at two points, just a centimeter or so apart. With this information, a smart phone can calculate a physiological indicator called pulse-wave velocity, which varies as blood pressure changes. The above process involves light; the sticker alternately flashes a red and an infrared LED and uses a photodetector to pick up the light reflected from the skin beneath the Biostamp. Because deoxygenated blood absorbs more red light and oxygenated blood absorbs more of the infrared, fluctuations in those levels create a waveform that represents the heartbeat. That’s basically how the newest fitness bands detect a pulse, though the Biostamp version can get a more stable signal because the skin doesn’t shift under it. Though presently a BioStamp cannot store energy, research is being conducted to make batteries similar to the above design. The chemical composition of the sweat is measured by colour changing chemicals on the sticker that react differently to different chemicals. The smartphone app then uses this degree of colour change o the different chemical components present on the sticker to estimate the chemical composition of the individual’s sweat.

Though a BioStamp wears off with the dying skin cells, and cannot be reused, the very cheap manufacturing costs helps the financial stress remain negligible.

Another concept of such ‘biostamp’ comes from an Austin-based start-up called Chaotic Moon which deals with software design and development. They have designed a “Tattoo” that maps the body’s status using conductive ink supported on a thin plastic/ rubber substrate of a few micrometers thickness. (Image Below)

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Though the tattoo kit is still in a development stage it has variety of uses including in military, like measuring stress, detect poison and pathogens, and also in medicine, to measure the blood pressure and temperature of the body.

 “The future of wearables is biowearables.”

Apart from these Zhenan Bao at Stanford is also working with organic semiconductors to develop an electronic film that would be as sensitive as human skin and could be applied over robotic limbs. And researchers at the University of California, San Diego, are developing inks that would allow scientists to draw sensors directly onto the skin. Scientists in Japan have also built a prototype of a “Screen on you skin”, which is basically polymer LEDs just 3 micrometers thick equipped with organic photodetectors. In a proof-of-concept (shown in the image below) the researchers from Univ. of Tokyo have mounted the LED on a flexible rubber substrate connected to a sensor that measures blood oxygen levels and then attached them to human skin using , essentially, clingfilm. The future of us ditching our smartwatches is quite near.

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In a comparably not-so-thin device, called the wearable thermo-electric generator, the engineers of Univ. of Carolina have made used of the temperature gradient between the skin and the surrounding air to produce electricity. Instead of using bulky heat sinks, the technology relies on a layer of thermally conductive material that is attached to the skin, spreading out heat. The conductive material is coated with a polymer that prevents the heat from dissipating through to the outside air. As a result, the body heat has to pass through a centrally-located TEG one centimetre squared in size. The device produces about 20 microwatt per centimeter square which is twenty times more than most of the other prototypes. This energy is stored in a battery. The device itself is just 2mm thin and flexible. The best place advised to wear it on is the upper arm, the waist though higher in temperature, has skin folds which reduces surface area which reduces the out put.

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A prototype for the Chaotic Moon tattoo kit

In a nutshell, the future seems better in terms of healthcare. We can hope to find everyone around us showing off cool tattoos that serve a bigger purpose than just fashion. The work of doctors and physical trainers will be made easy too because now they will have reliable data other than just to depend on the patients description of his body in between appointments, and thus medical procedures can be carried out accurately. Since the manufacturing costs are low, the fact that they cannot be reused can be neglected. And so, to end this post, I would just say, let’s get inked! (in the future ofcourse!)

-The Cosmogasmic Person

Links :

Chaotic Moon Tattoo Kit (Video)

BioStamp Website

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