Biofilm developed to power wearable electronics with sweat
CategoriesSustainable News

Biofilm developed to power wearable electronics with sweat

University of Massachusetts Amherst researchers have invented a biofilm that sticks to the skin like a Band-Aid to harnesses sweat for electricity that could power wearable devices.

The biofilm is made using a bacteria that converts energy from evaporation into electricity, making use of the moisture on a person’s skin as it turns into vapour.

The University of Massachusetts Amherst researchers behind the innovation say it takes advantage of the “huge, untapped source of energy” that is evaporation.

“This is a very exciting technology,” said team member and electrical and computer engineering graduate student Xiaomeng Liu. “It is real green energy, and unlike other so-called ‘green-energy’ sources, its production is totally green.”

Microbial biofilm powers a small LCD screen with the word 'Hello' written on it
The biofilm uses sweat to power small electronic devices such as an LCD screen

According to the researchers, this is because the film is produced naturally by the microbes, with no need for unsustainably produced materials and no toxic waste byproducts.

“We’ve simplified the process of generating electricity by radically cutting back on the amount of processing needed,” said microbiology professor Derek Lovley, who is one of the senior authors of a paper the team has published in the journal Nature Communications.

“We sustainably grow the cells in a biofilm, and then use that agglomeration of cells. This cuts the energy inputs, makes everything simpler and widens the potential applications.”

The bacteria used is called geobacter sulfurreducens and is known for its ability to produce electricity, having previously been used to make microbial batteries.

Unlike with those batteries, however, the biofilm bacteria do not need to be periodically fed or cared for, because they are already dead — one of the team’s discoveries is that the microbes do not need to be alive to produce electricity.

To obtain the biofilm, the researchers harvest the geobacter, which grows in colonies that look like thin sheets of under 0.1 millimetres thickness, with the microbes all connected to each other by “natural nanowires”.

Diagram showing the biofilm sandwiched in between two layers of mesh electrodes and two layers of biopolymer
The biofilm is sandwiched between electrodes and sticky biopolymer before being ready for use

The researchers etch small circuits into these mats and then sandwich them between two mesh electrodes before sealing the package in a soft, sticky biopolymer to enable it to grip to the skin.

They describe the act of applying the film to your body as akin to plugging in a battery, and say it could revolutionise wearable electronics by solving the problem of where to put the power supply.

“Batteries run down and have to be changed or charged,” said electrical and computer engineering professor Jun Yao. “They are also bulky, heavy and uncomfortable.”

In its current form the biofilm produces enough energy to power small devices such as medical sensors or personal electronics, but the team also plans to explore larger films that can power even more sophisticated devices.

At an even larger scale, they hope the biofilm could be used to make more use of the untapped energy from evaporation, pointing to research that shows around 50 per cent of the solar energy reaching earth is spent on the process.

An example of a microbial battery appears in the work of Dutch designer Teresa van Dongen, who has used the geobacters to produce the Electric Life lighting and the Mud Well installation.

She embraces the fact that the bacteria need to be fed, arguing that this ritual would create “a closer relationship between the (living) object and its owner”.

Reference

Wireless skin measures pulse, sweat, and UV exposure
CategoriesSustainable News

Wireless skin measures pulse, sweat, and UV exposure

Spotted: Most wearable health sensors today communicate via embedded Bluetooth chips. But these battery-powered chips are bulky meaning that they may not be suitable for the next generation of sensors. In response, a team of researchers at the Massachusetts Institute of Technology (MIT) is developing chip-free wireless sensors that are much smaller, more efficient, and self-powering.  

At the heart of the team’s innovation is a phenomenon called piezoelectricity. When certain materials are subjected to mechanical stress, they accumulate an electrical charge. One such material is a semiconductor called gallium nitride, which the MIT researchers used to create an ultra-thin, flexible film. This film, in turn, forms the basis of an electronic skin (‘e-skin’) that is highly responsive to both electrical and mechanical stimuli. The piezoelectric properties of gallium nitride are ‘two-way’. This means that the material produces electricity in response to mechanical strain, while also vibrating in response to an electrical impulse. As a result gallium nitride is ideal for both sensing and wireless communication. 

The research team’s e-skin works extremely well as a health sensor, sticking to human skin like sellotape. Because it is extremely sensitive, the e-skin can respond to a patient’s heartbeat and the presence of sweat. These stimuli cause it to vibrate, and these vibrations are sufficient to generate a small electrical current that can be read by a nearby wireless receiver. 

“Chips require a lot of power, but our device could make a system very light without having any chips that are power-hungry,” explains Jeehwan Kim, an associate professor of mechanical engineering and of materials science and engineering. “You could put it on your body like a bandage, and paired with a wireless reader on your cellphone, you could wirelessly monitor your pulse, sweat, and other biological signals.” 

The device is still under development, with the first successful outcomes recently published in the journal Science. Ultimately, the techniques used to create the sensor could pave the way for advances in everything from fitness tracking to medical diagnostics. 

Springwise has spotted a number of innovations aiming to improve wireless healthcare, these include ultrasound stickers for mobile monitoring of internal organs, also developed at MIT, and a flexible battery created by researchers at the Korea Institute of Machinery and Materials (KIMM). 

Written By: Katrina Lane

Email: jeehwan@mit.edu

Website: jeehwanlab.mit.edu

Reference