Medical Design Briefs - October 2021 - 44

GlobAl
INNOVATIONS
Tiny Biosupercapacitor Provides Energy for Biomedical
Applications
Chemnitz University of Technology, Chemnitz, Germany
he miniaturization of microelectronic
sensor technology, microelectronic
robots, and intravascular implants
is progressing rapidly. However, it also
poses major challenges for research. One
of the biggest is the development of tiny
but efficient energy storage devices that
enable the operation of autonomously
working microsystems - in more and
more small areas of the human body, for
example. In addition, these energy storage
devices must be biocompatible if they are
to be used in the body at all.
T
A newly developed prototype combines
these essential properties. The breakthrough
was achieved by an international
research team led by Prof. Dr. Oliver G.
Schmidt, professor of materials systems for
nanoelectronics at Chemnitz Uni versity of
Technology. The Leibniz Institute of
Polymer Research Dresden (IPF) was also
a cooperation partner.
The supercapacitors already function
in (artificial) blood vessels and can be
used as an energy source for a tiny sensor
system to measure pH.
This storage system opens up possibilities
for the developement of intravascular
implants and microrobotic systems
for next-generation biomedicine that
could operate in hard-to-reach small
spaces deep inside the human body. For
example, real-time detection of blood
pH could help predict early tumor growing.
The investigation was largely carried
out at the Research Center MAIN at
Chemnitz University of Technology.
■ Smaller Than a Speck of Dust
So-called biosupercapacitors (BSCs),
however, are fully biocompatible, which
means that they can be used in body fluids
such as blood and can be used for further
medical studies. Biosuper capacitors
can compensate for self- discharge be -
havior through bio-electrochemical re -
actions. In doing so, they even benefit
from the body's own reactions. The flexible
tubular geometry provides efficient
self-protection against deformations
44
Intro
Cov
An array of 90 tubular nanobiosupercapacitors
(nBSCs) on the fingertip enable autarkic operation
of sensors in blood. (Credit: Research
Group Prof. Dr. Oliver G. Schmidt)
caused by pulsating blood or muscle
contraction. At full capacity, it can operate
a complex, fully integrated sensor
system for measuring the pH value in
blood.
■ Flexible, Robust, Tiny
Origami structure technology involves
placing the materials required for the
nanobiosupercapacitors (nBSC) components
on a wafer-thin surface under high
mechanical tension. When the material
layers are subsequently detached from
the surface in a controlled manner, the
strain energy is released, and the layers
wind themselves into compact 3D
devices with high accuracy and yield (95
percent).
The nBSCs were tested in three electrolytes:
saline, blood plasma, and
blood. In all three electrolytes, energy
storage was sufficiently successful, albeit
with varying efficiency. In order to maintain
natural body functions in different
situations, the flow characteristics of the
blood and the pressure in the vessels are
under constant change. Any im -
plantable system within the circulatory
system must withstand these physiological
conditions while maintaining stable
performance.
The team, therefore, studied the performance
in microfluidic channels with
diameters of 120-150 µm (0.12-0.15
mm) to mimic blood vessels of different
sizes. They found that the nBSCs can provide
their power well and stably under
physiologically relevant conditions.
■ Self-Contained Sensor
The hydrogen potential (pH) of
blood is subject to fluctuations. Con -
tinuous measurement of the pH can
thus help in the early detection of
tumors, for example. For this purpose,
the researchers developed a pH sensor
that is supplied with energy by the nBSC.
The 5-µm thin film transistor technology
previously established by Schmidt's
research team could be used to develop
a ring oscillator with exceptional
mechanical flexibility, operating at low
power (nW to µW) and high frequencies
(up to 100 MHz).
The team used an nBSC-based ring
oscillator. The team integrated a pHsensitive
BSC into the ring oscillator so
that there is a change in output frequency
depending on the pH of the electrolyte.
This pH-sensitive ring oscillator
was also formed into a tubular 3D geometry
using the Swiss-roll origami technique,
creating a fully integrated and
ultra-compact system of energy storage
and sensor.
Prof. Dr. Oliver G. Schmidt is a pioneer in the
field of microrobotics and micromotors. (Credit:
Jacob Müller)
www.medicaldesignbriefs.com
ToC
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The researchers report on their
research in a recent issue of Nature
Communications.
For more information, visit https://www.
tu-chemnitz.de.
Medical Design Briefs, October 2021
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https://www.tu-chemnitz.de http://www.medicaldesignbriefs.com http://info.hotims.com/79418-966
Medical Design Briefs - October 2021

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