How to power a device using dirt, sweat or bacteria poop

I just got back from speaking at ARM’s annual tech event in Santa Clara, and I came back feeling confident in my vision for the future of our connected world but still wondering how we’re going to get there. I’m with SoftBank Chairman Masayoshi Son who believes by 2035 we will have a trillion connected devices.

To get there, we’re going to have to make some serious technological leaps. One of those leaps is in power. We can’t have people touching anywhere near a trillion sensors to change out batteries or replace unplugged cords.

The answer isn’t bigger batteries, it’s energy harvesting sensors. Already there may be devices in or near your home that convert mechanical energy to power. For example, the Hue Tap is a hockey-puck like remote control for Hue lights that contains a piezoelectric sensor instead of a battery. The City of Las Vegas has tested a lamp that’s powered by kinetic energy–specifically the footfalls of citizens walking near the lamp.

Other examples abound, but for the most part, the existing options generate very little power and can be expensive. The current main categories for energy harvesting technology still remain solar (power from the sun), pizeoelectric (mechanical and kinetic), thermoelectric (uses temperature differentials) and induction (a common form of wireless power).

But the potential for energy is all around us, and aside from the race to make photovoltaics (solar) more efficient, it can be hard to see what all is happening in the world of energy harvesting research. The big trend (and a necessary one) involves organics.

One challenge that needs to be addressed is wearables. Their small form factor and increasing power demands require more than solar power or kinetic energy from hand motions. One option to boost solar is to increase the surface area for the photosensitive cells that actually generate power. Researchers at the University of Texas at Austin are doing this using a paper made of cellulose produced by bacteria and nanocrystals.

A scalable process harnesses the bacterium Gluconacetobacter hansenii to produce dense nanocellulose membranes that are processed into paper. The nanoporous structure of the paper enables exceptional adhesion of the device layers and mitigates the impact of bending stresses that typically cause these brittle layers to crack.

In this case, more surface area means more power which is why foldable devices are so promising. This could be useful for a variety of devices, but especially bandages or stickers that attach to people’s skin to display biological data. Another useful energy generation technique for bandages or skin sensors comes from sweat.

This technique uses an enzyme that oxidizes the lactic acid in sweat to generate a current. It’s not a large current, but it could power a low power radio that can send data from a sensor. Like solar, the challenge associated with this technique is developing a greater energy density. Basically, it needs to generate more power over a smaller surface area.

And now for something completely different. For sensors in rivers, lakes and streams the Naval Research Lab has pioneered a battery that’s powered by bacteria moving within the water column. The negative end rests in the floor of the body of water and the positive end to sits within the water column. The current generated offers about .2 watts of power. These floating batteries could power water quality sensors for years.

Research is continuing in many other areas of energy generation, and many of them are relying more on organics than chemistry or physics. As we build more and more connected objects, I’m betting that organic and dynamic systems will be the way to go. For power, and to help solve other problems associated with a trillion connected devices.