Tech Briefs Magazine - December 2023 - MD-18

An Autonomous Battery-Free Microrobot Powered by
Surrounding Light
The robot uses a light sensor to move automatically toward light sources so it can run indefinitely on
harvested power.
University of Washington, Seattle, WA
S
mall mobile robots carrying sensors
could perform tasks like catching gas
leaks or tracking warehouse inventory. But
moving robots demands a lot of energy,
and batteries, the typical power source,
limit lifetime and raise environmental concerns.
Researchers at the University of
Washington have now created MilliMobile,
a tiny, self-driving robot powered only by
surrounding light or radio waves.
Equipped with a solar panel-like energy
harvester and four wheels,
MilliMobile is about the size of a penny,
weighs as much as a raisin and can move
about the length of a bus (30 feet, or 10
meters) in an hour even on a cloudy day.
The robot can drive on surfaces such as
concrete or packed soil and carry nearly
three times its own weight in equipment
like a camera or sensors. It uses a light
sensor to move automatically toward
light sources so it can run indefinitely on
harvested power.
" We took inspiration from 'intermittent
computing,' which breaks complex programs
into small steps, so a device with very
limited power can work incrementally, as
energy is available, " said co-lead author
Kyle Johnson, a UW doctoral student in
the Paul G. Allen School of Computer
Science & Engineering. " With MilliMobile,
we applied this concept to motion. We reduced
the robot's size and weight so it
takes only a small amount of energy to
move. And, similar to an animal taking
steps, our robot moves in discrete increments,
using small pulses of energy to turn
its wheels. "
The team tested MilliMobile both indoors
and outdoors, in environments
such as parks, an indoor hydroponic
farm and an office. Even in very low light
situations - for instance, powered only
by the lights under a kitchen counter
- the robots are still able to inch along,
though much slower. Running continuously,
even at that pace, opens new abilities
for a swarm of robots deployed in
areas where other sensors have trouble
generating nuanced data.
18
Researchers at the University of Washington have now created MilliMobile, a tiny, self-driving robot powered
only by surrounding light or radio waves. It's about the size of a penny and can run indefinitely on harvested
energy. (Image: Mark Stone/University of Washington)
The tiny robot is able to move across a variety of surfaces, including concrete and packed soil. (Image: Mark
Stone/University of Washington)
These robots are also able to steer themselves,
navigating with onboard sensors
and tiny computing chips. To demonstrate
this, the team programmed the robots to
use their onboard light sensors to move
towards a light source.
" 'Internet of Things' sensors are usually
fixed in specific locations, " said co-lead
author Zachary Englhardt, a UW doctoral
student in the Allen School. " Our work
crosses domains to create robotic sensors
that can sample data at multiple points
throughout a space to create a more detailed
view of its environment, whether
that's a smart farm where the robots are
tracking humidity and soil moisture, or a
factory where they're seeking out electromagnetic
noise to find equipment malfunctions. "
Researchers
have outfitted MilliMobile
with light, temperature, and humidity sensors
as well as with Bluetooth, letting it
transmit data over 650 feet (200 meters).
In the future, they plan to add other sensors
and improve data-sharing among
swarms of these robots.
For more information, contact
millimobile@cs.washington.edu.
Motion Design, December 2023

Tech Briefs Magazine - December 2023

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