Tech Briefs Magazine - October 2021 - MD-17

Hydrodynamic Effect Helps Motorized Objects
Navigate Inclines
The tiny motors mimic how rock climbers navigate inclines.
New York University, New York, New York
Scientists have uncovered how heavy,
motorized objects climb steep slopes
- a newly discovered mechanism that
also mimics how rock climbers navigate
inclines. The finding stems from a series
of experiments in which motorized
objects were placed in liquid and then
moved up tilted surfaces. These " microswimmers "
are about 20 times heavier
than the fluid they swim in but they were
able to climb almost vertical steep slopes.
Gravitaxis - directional movement in
response to gravity - is a vital phenomenon
not only in engineering but also in
medicine and pharmaceutical development.
It explains, in part, how bacteria
move through the body and provides
insights into ways to create more effective
drug-delivery mechanisms.
The motorized swimmers, or nanorods,
are roughly 1/40th the width of a strand
of human hair and were tasked with moving
up an inclined surface while im -
mersed in a liquid solution within a walled
container. The swimmers were composed
of two types of metal: gold and rhodium
as well as gold and platinum - a make-up
that gave them unbalanced densities
given the varying weights of these metals.
The swimmers' composition, liquid environment,
and juxtaposition of surfaces
enabled them to move upward, despite
their significant weight.
Heavy metallic microswimmers, made of rhodium (purple) and gold, swim around in a liquid solution. When confronting
a sloped wall, each rod-like swimmer will reorient its body upward due to its density imbalance and
swim up like a rock climber against gravity. A hydrodynamic effect helps to amplify the action in its reorientation.
(Image: Jun Zhang, NYU's Courant Institute and NYU's Department of Physics)
The motors reorient themselves up -
ward against gravity thanks to their density
imbalance, much like a seesaw reorients
itself in response to the movement
and weight of its riders. A hydrodynamic
effect amplifies this movement - swimming
next to a wall yields a bigger
torque in repositioning the motors' bodies
upwards. Future motors will be de -
signed to reach targeted locations and to
perform designated functions.
For more information, contact James
Devitt at james.devitt@nyu.edu; 212-9986808.
Magnets
Improve Control of Prosthetic Limbs
A system uses tiny magnetic beads to rapidly measure the position of muscles and relay that
information to a bionic prosthesis.
Massachusetts Institute of Technology, Cambridge
For people with prosthetic limbs, one
of the greatest challenges is controlling
the prosthesis so that it moves the
same way a natural limb would. Most
prosthetic limbs are controlled using
electromyography - a way of recording
electrical activity from the muscles -
Motion Design, October 2021
Cov
ToC
but this approach provides only limited
control of the prosthesis.
Researchers developed an alternative
approach that could offer much more
precise control of prosthetic limbs. After
inserting small magnetic beads into muscle
tissue within the amputated residuum,
they can precisely measure the
length of a muscle as it contracts and
this feedback can be relayed to a bionic
prosthesis within milliseconds. The strategy,
called magnetomicrometry (MM),
can provide fast and accurate muscle
measurements.
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Tech Briefs Magazine - October 2021

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