Tech Briefs Magazine - June 2021 - MD-17

Chemically Driven Wheels " Morph " Into Gears
A catalytic reaction causes a two-dimensional, chemically coated sheet to spontaneously
morph into a three-dimensional gear.
University of Pittsburgh, Pennsylvania
The gear is one of the oldest me -
chanical tools and led to ma -
chines ranging from early irrigation
systems and clocks, to modern
engines and robotics. Researchers
have utilized a catalytic reaction that
causes a two-dimensional, chemically
coated sheet to spontaneously
" morph " into a three-dimensional
gear that performs sustained work.
The findings indicate the potential
to develop chemically driven
ma chines that do not rely on external
power but simply require the
addition of reactants to the surrounding
solution. Computational
modeling has shown that chemomechanical
transduction (conversion
of chemical energy into mo -
tion) at active sheets presents a
novel way to replicate the behavior
of gears in environments without
access to traditional power sources.
In the simulations, catalysts are
placed at various points on a twodimensional
sheet resembling a
wheel with spokes, with heavier
nodes on the sheet's circumference.
The flexible sheet, approximately
a millimeter in length, is then
placed in a fluid-filled microchamber.
A reactant is added to the chamber
that activates the catalysts on the flat
14
12
10
8
6
4
2
2
1
05
10
Transmission of rotational motion from an active gear to two passive
gears. In a fluidic chamber, an active gear can rotate multiple passive
gears, which are placed to break the symmetry of the flow field.
" wheel, " thereby causing the fluid to
spontaneously flow. The inward fluid
flow drives the lighter sections of the
sheet to pop up, forming an active
rotor that catches the flow and rotates.
In nature, organisms use chemical
energy to change their shape
and move. For the new chemical
sheet to move, it also has to spontaneously
morph into a new shape,
which allows it to catch the fluid
flow and perform its function.
The team found that not all the
gear parts needed to be chemically
active for motion to occur; in fact,
asymmetry is crucial to create
movement. By determining the
design rules for the placement, the
researchers could direct the rotation
to be clockwise or counterclockwise.
This added " program "
enabled the control of indepen -
dent rotors to move sequentially or
in a cascade effect, with active and
passive gear systems. This more
complex action is controlled by the
internal structure of the spokes
and the placement within the fluid
domain.
In the future, the researchers
will investigate how the relative
spatial organization of multiple
gears can lead to greater functionality,
potentially designing a system
that appears to act as if it were making
decisions.
For more information, contact Paul
Kovach at pkovach@pitt.edu.
Air-Powered Robot Needs No Electronics
The walking quadruped is controlled and powered by pressurized air.
University of California, San Diego
Engineers have created a four-legged
soft robot that doesn't need any electronics
to work. The robot only needs a
constant source of pressurized air for all
its functions including its controls and
locomotion systems. Applications in -
clude robots that can operate in environments
where electronics cannot function
such as MRI machines or mine
shafts. Soft robots are of particular interMotion
Design, June 2021
Cov
ToC
est because they easily adapt to their
environment and operate safely near
humans.
Most soft robots are powered by pressurized
air and are controlled by electronic
circuits. But this approach re -
quires complex components like circuit
boards, valves, and pumps, often outside
the robot's body. These components,
which constitute the robot's brains and
nervous system, are typically bulky and
expensive. By contrast, the new robot is
controlled by a lightweight, low-cost system
of pneumatic circuits, made up of
tubes and soft valves onboard the robot
itself. The robot can walk on command
or in response to signals it senses from
the environment.
The robot's computational power
roughly mimics mammalian reflexes
17
http://www.abpi.net/ntbpdfclicks/l.php?202106TBNAV
Tech Briefs Magazine - June 2021

Table of Contents for the Digital Edition of Tech Briefs Magazine - June 2021
