Human batteries to power wearables

Technology is emerging that could one day make it possible for humans to be the batteries that power wearable devices

At MPN we have seen a growing trend of wearable devices and medical implants that require batteries.

We originally went delving into the world of battery technology to find out how future medical devices could benefit from smaller batteries.

However, once there, we made the intriguing discovery that humans could actually become the batteries.

A lot of this tech in is in the early stages of its development, yet we want to show what the future of batteries and wearables could be.

This is not sorcery, this is not sci-fi, these are materials, blood, sweat and tears.

Piezoelectric Materials

Researchers have started to utilize a unique property of some materials, known as piezoelectricity, to generate electricity from kinetic energy.

Think ‘wind-up torch’, and how it converts kinetic energy to electricity, it’s the same principle.

In 2013 an elastomer-based piezoelectric fabric was developed by Dr. Ville Kaajakari which was able to generate electricity using only the kinetic energy of human motion.

This piece of fabric was worn in the shoe insole of a volunteer and their walking generated enough electricity to illuminate 30 LEDs.

This same fabric was applied onto a shirt, which was artificially moved for a few hours, and generated enough energy to charge a lithium-ion battery.

Now imagine a future with this type of material being used in wearable devices, for example the Cityzen smart shirt with a battery that is powered by the athletes while they are wearing it.

Piezoelectric material has also been used to harvest energy from internal organs.

In 2014 US-based researchers attached ultra-thin piezoelectric material to the organs of (sedated) cows and sheep.

The fabric implanted around those moving organs generated about a microwatt of power, which may not sound that impressive, but is roughly the amount needed to run a cardiac pace maker.

Now imagine a future that has a pace maker, for humans, without the nasty complications that come from wires attaching the pacemaker to the battery pack.

Blood - EFCs

In order to function properly our cells require a continuous supply of chemical energy.

Enzymatic biofuel cells (EFCs) are small, battery-like devices that can generate electricity by breaking down the energy-rich chemicals in bodily fluids, and blood is one of the most energy-rich fluids in the entire body.

In 2012 a team of French researchers constructed a carbon nanotube-based EFC.

They implanted this device into a rat’s abdomen and it generated around 40 microwatts of power, from the glucose in the rat’s blood, which the team used to operate an LED and a digital thermometer.

Granted, this tech comes with the disadvantage that the user would have to be cut open in order to insert the EFC, but people having implants would already be having surgery.

Imagine a future with hearing aids that can be implanted inside the wearer’s ears and run from the glucose in their blood.

Sweat – EFCs

Human sweat is rich in a compound called lactate that can also be used to generate electricity through EFCs.

Researchers have already been able to test perspiration-powered EFCs on humans.

In 2014 UC San Diego came up with a wearable, textile-based EFC that could be integrated into temporary tattoos and armbands.

A volunteer wore one of the armbands while riding a bike and the sweat produced enough power to run an electronic device, an LED or digital watch, for a few tens of seconds.

This is admittedly not as impressive as the Piezoelectric Materials or Blood EFCs results, but is still a technological marvel.

Tears – EFCs

This next tech uses the film of ‘basal’ tears that keep eyes moist in order to create energy.

Basal tears contain glucose, lactate and ascorbate, all of which are appropriate fuel sources for EFCs.

One advantage of using tears to power electronics is that a perfect platform already exists on which to mount the hardware – Contact Lenses.

If a self-sustained fuel cell could be integrated into contact lenses the future technological applications could be nothing short of revolutionary.

Russ Reid, a bioengineer at the University of Utah, and his colleagues have recently developed the first-ever contact lens with an integrated EFC, allowing it to generate electricity from human tears alone.

Their prototype consists of an elastomer lens with two thin carbon fiber electrodes wrapped around its perimeter, leaving the center of the lens unobscured.

It has not yet been tested in humans, but when Reid and colleagues bathed the lens in a synthetic tear solution, it maintained a power output of over one microwatt for three hours.

Without EFC powered lenses, Google are already developing contact lenses which are designed to measure the glucose level of people with diabetes.

Imagine what Reid’s tech could do if it was combined with the smart contact prototype by Google and Alcon.

There is every possibility that future wearables devices could be powered by humans.