Battery-free wireless devices that float in the wind



Plants cover a large fraction of the Earth’s land mass despite most species having limited to no mobility. Many plants have evolved mechanisms to disperse their seeds using the wind. A dandelion seed, for example, can travel as far as a kilometer in dry, windy, and warm conditions. Inspired by this, we demonstrate wind dispersal of battery-free wireless sensing devices. Our millimeter-scale devices are designed on a flexible substrate using programmable, off-the-shelf parts to enable scalability and flexibility for various sensing and computing applications. The system is powered using lightweight solar cells and an energy harvesting circuit that is robust to low and variable light conditions and has a backscatter communication link that enables data transmission. To achieve the wide-area dispersal and upright landing that is necessary for solar power harvesting, we developed dandelion-inspired, thin-film porous structures that achieve a low terminal velocity and have an aerodynamic stability with a probability of upright landing of over 95%. Our results in outdoor environments demonstrate that these devices can travel 50–100 meters in gentle to moderate breeze. Finally, in natural systems, variance in individual seed morphology causes some seeds to fall closer and others to travel farther. We adopt a similar approach and show how we can modulate the porosity and diameter of the structures to achieve dispersal variation across devices. This demonstrate an exciting vision where hundreds to thousands of battery-free devices can be dispersed across a large area like farms, forests, glaciers and other hard to reach areas in order to achieve planetary-scale environmental sensing.


Publications

Wind-dispersal of battery-free wireless devices [paper]
Vikram Iyer, Hans Gaensbauer, Thomas Daniel, Shyamnath Gollakota, Nature 2022




Links

Code
UW Networks & Mobile Systems Lab




Creating the Internet of biological and bio-inspired things

This work is part of our broader vision of creating the Internet of bio-inspired and biological things. Specifically, there’s a pretty big gap between biological systems and the capabilities of current IoT and embedded systems, which are much larger and heavier and most can’t move around. Instead, imagine, if we can create tiny battery-free wireless devices that can move around, and in fact float in the air similar to dandelion seeds. If we could do that we could deploy hundreds of sensors in the wind in remote, hard-to-reach areas like forests, glaciers. Or if we create wireless sensors that are so small, then we can also start attaching them to tiny insects like bees, beetles and murder hornets then we can use these sensors to study their behavior in the wild. If we can go a step further to integrate actuators with these wireless sensors, we can enable them to move around freely and build insect-scale robots.

The common enabling technology that runs through all of these, is using programmable, general purpose computing devices to build these tiny wireless systems. This approach enables rapid prototyping and innovation that was not possible before at this scale. The traditional approach to make things small, has been to build custom ICs. But custom chips have high fabrication costs and long, multi-year design cycles, and they are often built for a specific purpose and can be hard to reuse. The key insight here is to instead use programmable, general purpose computing chips like microcontrollers to build these millimeter scale wireless sensors. For example, the smallest commercial microcontroller is only 1.5x1.4mm. And while it has limited computation and lacks common hardware interfaces for sensors, it’s programmable which allows us to implement common protocols like I2C to talk to sensors using software. And while it doesn’t have a radio either, we can use a technique called backscatter to create tiny battery-free wireless sensors using these off-the-shelf components. The really powerful thing about this approach, is that by eliminating the need to design custom silicon, it empowers anyone with a computer engineering background to build tiny wireless devices.