Medical Design Briefs - January 2023 - 28

Wireless, High-Speed, Low-Power Communications for
Implantable Devices
The technique uses the
body's naturally occurring
ions to help transmit data.
Columbia University
New York, NY
Implantable bioelectronics are now
often key in assisting or monitoring the
heart, brain, and other vital organs, but
they often lack a safe, reliable way of
transmitting their data to doctors. Now
researchers at Columbia Engineering
have invented a way to augment implantable
bioelectronics with simple,
high-speed, low-power wireless data
links using ions, positively or negatively
charged atoms that are naturally available
in the body.
Implantable bioelectronics are increasingly
playing key roles in healthcare.
For example, pacemakers can
help ensure that a patient's heart maintains
a healthy beat, and neural interface
devices can assist patients with epilepsy
and other disorders by stimulating
specific brain regions to reduce their
neurological symptoms, or even link a
paralyzed patient's brain with robotic
limbs. However, one major challenge
that implanted bioelectronics face is
how to communicate their data through
the body to external devices for further
analysis and diagnostics by physicians
and scientists.
" From brain or muscle activity to hormone
concentrations, these data need
to be transmitted so that they can undergo
advanced processing and review by
experts before medical decision-making
occurs, "
says study co-senior
author
Dion Khodagholy, an associate professor
of electrical engineering at Columbia
University.
" This is especially important for conditions
where there can be substantial fluctuations
over time, such as in epilepsy or
movement disorders, " adds study co-senior
author Jennifer Gelinas, an assistant professor
of neurology at Columbia University
Irving Medical Center. " One example of
this is the NeuroPace device for epilepsy
- the data from it needs to be downloaded
for the clinician to adjust its stimulation
protocols to better treat seizures. "
28
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TX
V
RX
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Frequency (Hz)
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Ionic communication: Cross-sectional schematic
illustration
of
an
ionic
communication
sisting of an implanted transmitter
is
capacity
to
operate
device
con(TX)
electrode
pair inside biological tissue and a receiver electrode
pair (RX) on the surface of the tissue (top
left). Frequency responses of ionic communication
highlighting
at megahertz
frequencies (top right). A 10-link ionic communication
transmitter (TX) and receiver (RX) array conforming
to the surface of an orchid petal (bottom).
(Credit: Dion Khodagholy/Columbia Engineering)
Although cables offer a simple way to
quickly transmit data from implants to
outside machines, the way they penetrate
tissue limits their long-term use. At
the same time, conventional wireless approaches
using radio waves or visible
light often do a poor job penetrating
bio logical tissue.
" Safe, effective, long-term wireless
com munications with implanted devices
is still lacking, " Khodagholy says.
n Making Use of the Body's Ions
An intriguing strategy that bioelectronics
could use for communications is
one the body often uses - ions. Inside
the body, cells regularly shuffle ions
around to communicate with each other.
Now Khodagholy and his colleagues
have developed a way to use the body's
ions to transmit data at megahertz rates
- that is, millions of bits per second.
Their study, " Ionic communication for
implantable bioelectronics, " appears in
Science Advances.
www.medicaldesignbriefs.com
The way in which living tissues are rich
with ions means they store electrical potential
energy, much as electric batteries
do. The new technique, dubbed ionic
communication, leverages this fact to
help implanted bioelectronics exchange
data with external devices.
Ionic communication involves one
pair of electrodes implanted inside a
tissue, and another pair of electrodes
resting on the surface of that tissue.
The implanted device encodes data in
alternating electric pulses that store energy
within the tissue. In turn, the surface
receiver can detect this energy and
decode it.
In the new study, the researchers detailed
what geometric properties govern
the depths to which ionic communication
might reach inside the body, as well
as strategies to establish multiple parallel
lines of communication between electrodes.
They found ionic communication
was capable of transmitting data
across distances that could help it target
a variety of tissue types, from human skin
to visceral organs.
" Ionic communication is a biologically
based form of data communication
that establishes long-term, high-fidelity
interactions across intact tissue, "
Khodagholy says.
Medical Design Briefs, January 2023
Anisotropic ion conducting particulate composite
(AIC): Schematic illustration of AIC cross section
composed of ions (red and blue), conducting
particles (gray), and insulating scaffold (blue);
black lines indicate the vertical conduction path
(top). Scanning electron microscopy cross-sectional
image of AIC film. Colors highlight the sodium
polystyrene sulfonate particles (red, 10
µm) and the polyurethane scaffold (purple).
(Credit: Dion Khodagholy/Columbia Engineering)
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Medical Design Briefs - January 2023

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