Medical Design Briefs - January 2025 - 29

ing to scrape away any material that remains
between individual devices. Finally,
they dissolve the sacrificial layer in
water, leaving thousands of microscopic
devices freely floating in the liquid.
Once they have a solution with
free-floating devices, they wirelessly actuated
the devices with light to induce the
devices to roll. They found that free-floating
structures can maintain their shapes
for days after illumination stops.
The researchers conducted a series of
experiments to ensure that the entire
method is biocompatible.
After perfecting the use of light to
control rolling, they tested the devices
on rat neurons and found they could
tightly wrap around even highly curved
axons and dendrites without causing
damage.
" To have intimate interfaces with
these cells, the devices must be soft and
able to conform to these complex structures.
That is the challenge we solved in
this work. We were the first to show that
azobenzene could even wrap around living
cells, " she says.
Among the biggest challenges they
faced was developing a scalable fabrication
process that could be performed
outside a clean room. They also iterated
on the ideal thickness for the devices,
since making them too thick causes
cracking when they roll.
Because azobenzene is an insulator,
one direct application is using the devices
as synthetic myelin for axons that
have been damaged. Myelin is an insulating
layer that wraps axons and allows
electrical impulses to travel efficiently
between neurons.
In non-myelinating diseases like multiple
sclerosis, neurons lose some insulating
myelin sheets. There is no biological way
of regenerating them. By acting as synthetic
myelin, the wearables might help
restore neuronal function in MS patients.
The researchers also demonstrated
how the devices can be combined with
optoelectrical materials that can stimulate
cells. Moreover, atomically thin materials
can be patterned on top of the
devices, which can still roll to form microtubes
without breaking. This opens
up opportunities for integrating sensors
and circuits in the devices.
In addition, because they make such
a tight connection with cells, one could
use very little energy to stimulate subcellular
regions. This could enable a
researcher or clinician to modulate
electrical activity of neurons for treating
brain diseases.
" It is exciting to demonstrate this symbiosis
of an artificial device with a cell at
an unprecedented resolution. We have
shown that this technology is possible, "
Sarkar says.
In addition to exploring these applications,
the researchers want to try functionalizing
the device surfaces with molecules
that would enable them to target
specific cell types or subcellular regions.
" This work is an exciting step toward
new symbiotic neural interfaces acting at
the level of the individual axons and synapses.
When integrated with nanoscale
1- and 2D conductive nanomaterials,
these light-responsive azobenzene sheets
could become a versatile platform to
sense and deliver different types of sigMedical
Design Briefs, January 2025
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Medical Design Briefs - January 2025

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