Tech Briefs Magazine - November 2023 - 44

Mechanical &
Fluid Systems
tionary patch changes (from completely
covered, to half covered, to not covered
at all), each patch individually detects
the resulting change in capacitance.
The floating capacitor is not connected
to any circuitry, so wires won't get tangled
with rotating components. Rather, the stationary
patches are wired to electronics
that use software the researchers developed
to convert raw sensor data into estimations
of angular position, direction of
rotation, and rotation speed.
To simplify the sensor integration process
for a user, the researchers built a SolidWorks
extension. A maker specifies the
rotating and stationary parts of their mechanism,
as well as the center of rotation, and
then the system automatically adds sensor
patches to the model.
The researchers used their system to
prototype several devices, including a
smart desk lamp that changes the color
and brightness of its light depending on
how the user rotates the bottom or middle
of the lamp. They also produced a planetary
gearbox and a wheel that measures
distance as it rolls across a surface.
In addition to testing different materials,
AlAlawi and her collaborators plan to
explore how they could increase the robustness
of their sensor design to external
noise, and also develop printable sensors
for other types of moving mechanisms.
For more information, contact Abby
Abazorius at abbya@mit.edu; 617-2532709.
On/Off
Functionality for Fast, Sensitive, Ultra-Small
Technologies
An ultra-small actuator has nanometer-scale precision.
Osaka University, Osaka, Japan
T
o turn an ultra-small component
on and off, one requires an actuator
- a device that transmits an input,
such as electricity, into physical
motion. Actu ators in small-scale technologies
to date have critical limitations;
for example, if it's difficult to
integrate the actuator into semiconductor
electronics, real-world applications
of the technology will be limited.
An actuator design that operates
quickly, has precise on/off control,
and is compatible with modern electronics
would be immensely useful.
Researchers have developed an
actuator with high sensitivity, fast
on/off
re sponse, and
nanometer-scale
precision that is based on
vanadium oxide crystals. Many current
technologies use a property of
vanadium oxide known as the phase
transition
to
cause
out-of-plane
bending motions within small-scale
devices; for example, such actuators
are useful in ultra-small mirrors. Using
the phase transition to cause inplane
bending is far more difficult
but would be useful in ultra-small
grippers in medicine.
68 °C
M-VO2
R-VO2
30 °C
90 °C
1 µm
Bright-field microscopy image of a VO2
At 68 °C, vanadium oxide undergoes a
sharp monoclinic-to-rutile phase transition
that's useful in microscale technologies.
The team used a chevron-type (sawtooth)
device geometry to amplify
in-plane bending of the crystal. Using a
two-step protocol, they fabricated a
15-micrometer-long vanadium oxide
crystal attached by a series of 10-micrometer
arms to a fixed frame. By means of a
phase transition caused by a readily at44
chevron-type
planar actuator. Superposition in false color of the
tip of the shuttle at low and high temperature (bar, 1 μm).
tainable stimulus - a 10 °C temperature
change - the crystal moves 225 nanometers
in-plane. The expansion behavior
is highly reproducible over thousands
of cycles and several months.
The actuator also was moved in-plane
in response to a laser beam. The on/off
response time was a fraction of a millisecond
near the phase transition temperature,
with little change at other
temperatures.
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Small-scale technologies such as advanced
implanted drug delivery devices
wouldn't work without the ability to
rapidly turn them on and off. The underlying
principle of the actuator - a
reversible phase transition for on/off,
in-plane motion - will dramatically expand
the utility of many modern technologies
such as microrobotics.
For more information, contact kouhou@
office.osaka-u.ac.jp; +81-6-6879-7017.
Tech Briefs, November 2023
http://www.techbriefs.com
Tech Briefs Magazine - November 2023

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