Researchers have developed a method to
make adaptive and eco-friendly sensors that can be directly and imperceptibly
printed onto a wide range of biological surfaces, whether that's a finger or a
flower petal. Credit: University of Cambridge
Researchers
have developed a method to make adaptive and eco-friendly sensors that can be
directly and imperceptibly printed onto a wide range of biological surfaces,
whether that's a finger or a flower petal.
The method, developed by researchers
from the University of Cambridge, takes its inspiration from spider silk, which can conform and stick to a range of surfaces.
These "spider silks" also incorporate bioelectronics, so that
different sensing capabilities can be added to the "web."
The fibers, at least 50 times smaller
than a human hair, are so lightweight that the researchers printed them
directly onto the fluffy seedhead of a dandelion without collapsing its
structure. When printed on human skin, the fiber sensors conform to the skin
and expose the sweat pores, so the wearer doesn't detect their presence. Tests
of the fibers printed onto a human finger suggest they could be used as
continuous health monitors.
This low-waste and low-emission method
for augmenting living structures could be used in a range of fields, from
health care and virtual reality, to electronic textiles and environmental
monitoring. The results are
reported in the journal Nature
Electronics.
Although human skin is remarkably sensitive, augmenting it with
electronic sensors could fundamentally change how we interact with the world
around us. For example, sensors printed directly onto the skin could be used
for continuous health monitoring, for understanding skin sensations, or could
improve the sensation of reality in gaming or virtual reality applications.
While wearable technologies with embedded sensors, such as smartwatches, are widely available, these devices can be uncomfortable, obtrusive and can inhibit the skin's intrinsic sensations.
Researchers have developed a method to make
adaptive and eco-friendly sensors that can be directly and imperceptibly
printed onto a wide range of biological surfaces, whether that's a finger or a
flower petal. Credit: University of Cambridge
"If you want to accurately
sense anything on a biological surface like skin or a leaf, the interface
between the device and the surface is vital," said Professor Yan Yan Shery
Huang from Cambridge's Department of Engineering, who led the research.
"We also want bioelectronics that are completely imperceptible to the
user, so they don't in any way interfere with how the user interacts with the
world, and we want them to be sustainable and low waste."
There are multiple methods for
making wearable sensors, but these all have drawbacks. Flexible electronics,
for example, are normally printed on plastic films that don't allow gas or
moisture to pass through, so it would be like wrapping your skin in plastic
film. Other researchers have recently developed flexible electronics that are
gas-permeable, like artificial skins, but these still interfere with normal
sensation, and rely on energy- and waste-intensive manufacturing techniques.
3D printing is another potential
route for bioelectronics since it is less wasteful than other production
methods, but leads to thicker devices that can interfere with normal behavior.
Spinning electronic fibers results in devices that are imperceptible to the
user, but without a high degree of sensitivity or sophistication, and they're
difficult to transfer onto the object in question.
Now, the Cambridge-led team has
developed a new way of making high-performance bioelectronics that can be
customized to a wide range of biological surfaces, from a fingertip to the
fluffy seedhead of a dandelion, by printing them directly onto that surface.
Their technique takes its inspiration in part from spiders, who create
sophisticated and strong web structures adapted to their environment, using
minimal material.
The researchers spun their
bioelectronic "spider silk" from PEDOT:PSS (a biocompatible
conducting polymer), hyaluronic acid and polyethylene oxide. The
high-performance fibers were produced from water-based solution at room temperature, which enabled the researchers to control the
"spinnability" of the fibers. The researchers then designed an
orbital spinning approach to allow the fibers to morph to living surfaces, even
down to microstructures such as fingerprints.
Tests of the bioelectronic fibers, on surfaces including human fingers and dandelion seedheads, showed that they provided high-quality sensor performance while remaining imperceptible to the host.
Researchers have developed a method to make
adaptive and eco-friendly sensors that can be directly and imperceptibly
printed onto a wide range of biological surfaces, whether that's a finger or a
flower petal. Credit: University of Cambridge
"Our spinning approach allows
the bioelectronic fibers to follow the anatomy of different shapes, at both the
micro and macro scale, without the need for any image recognition," said
Andy Wang, the first author of the paper. "It opens up a whole different
angle in terms of how sustainable electronics and sensors can be made. It's a
much easier way to produce large area sensors."
Most high-resolution sensors are
made in an industrial cleanroom and require toxic chemicals in a multi-step and
energy-intensive fabrication process. The Cambridge-developed sensors can be
made anywhere and use a tiny fraction of the energy that regular sensors
require.
The bioelectronic fibers, which are
repairable, can be simply washed away when they have reached the end of their
useful lifetime, and generate less than a single milligram of waste. By
comparison, a typical single load of laundry produces between 600 and 1,500
milligrams of fiber waste.
"Using our simple fabrication
technique, we can put sensors almost anywhere and repair them where and when
they need it, without needing a big printing machine or a centralized
manufacturing facility," said Huang. "These sensors can be made on
demand, right where they're needed, and produce minimal waste and
emissions."
The researchers say their devices could be used in applications from health monitoring and virtual reality, to precision agriculture and environmental monitoring. In the future, other functional materials could be incorporated into this fiber printing method, to build integrated fiber sensors for augmenting the living systems with display, computation, and energy conversion functions. The research is being commercialized with the support of Cambridge Enterprise, the University's commercialization arm.
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