4 research outputs found
Wearable and Stretchable Soft Electronics Based on Ultrathin Gold Nanowires
Wearable and highly
flexible or stretchable electronics, including sensing devices, electrode
components and energy storage devices are essential component for future human
machine interfaces and bio monitoring. However, such electronics meet
difficulties on current rigid and brittle wafer-based electric circuitry
system. An alternative solution is to integrate the attributes of flexibility
and stretchability of novel materials or novel structures to realize soft
electronics. Nanotechnology offers new opportunities in designing soft
electronics. <br>
Ā Ā Ā Despite impressive recent advances, it remains challenging to
achieve high conductivity, high stretchability and ultrathin device dimension
into a single type of soft electronic device. Ultrathin gold nanowires (Au NWs)
are mechanically flexible yet robust, which exhibited serpentine structure at
nanoscale behaving like āpolymer chainsā due to their ultrathin nature (2 nm in
width, with an aspect ratio of >10,000). Hence, the Au NWs is intrinsically
stretchable thus showing great potential in constructing novel soft
electronics. <br>
Ā Ā Ā To address the existing challenges, this thesis introduces a
bunch of novel soft and wearable electronics based on ultrathin Au NWs. In
details, we designed and fabricated highly sensitive pressure sensor, highly
stretchable strain gauge sensor, flexible and transparent electrode,
stretchable and transparent supercapacitor for the application of wearable
biomedical monitoring, sports tracking, human machine interfacing and wearable
energy supplier. In addition, ultrathin Au NWs possess several unique feature
to soft electronics: 1) high sensitivity: a piezoresistive pressure sensor with
sensitivity of 1.14/kPa can be achieved, which allowed real-time monitoring of
human wrist pulse and tiny acoustic vibration. 2) High stretchability: a strain
gauge sensor based on Au NWs thin film with thickness of only 1.64 Ī¼m could be
working at strains exceeding 350%, >100 times larger than its metal
counterparts. 3) High transparency and conductivity: we explored a simple yet
efficient solution-based bottom-up strategy to fabricate Au NWs mesh film which
could achieve both high transparency (>92%) and conductivity. 4) Ultrathin
device dimensions: due to soft and serpentine-like geometry of ultrathin Au
NWs, well-aligned Au NWs thin film (8 nm in thickness) could achieve high
transparency (>90% at 550 nm) and excellent stretchability (>50%) simultaneously.
<br>
Ā Ā Ā Thus, the aim of this project is to develop a general and
inexpensive strategy to construct wearable electronic devices based on
ultrathin gold nanowires. We believed our strategies opened a new route to
future wearable electronics. <br>
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Manufacturable Conducting Rubber Ambers and Stretchable Conductors from Copper Nanowire Aerogel Monoliths
We report on a low-cost, simple yet efficient strategy to fabricate ultralightweight aerogel monoliths and conducting rubber ambers from copper nanowires (CuNWs). A trace amount of poly(vinyl alcohol) (PVA) substantially improved the mechanical robustness and elasticity of the CuNW aerogel while maintaining a high electrical conductivity. The resistivity was highly responsive to strains manifesting two distinct domains, and both followed a power law function consistent with pressure-controlled percolation theory. However, the values of the exponents were much less than the predicted value for 3D systems, which may be due to highly porous structures. Remarkably, the CuNW-PVA aerogels could be further embedded into PDMS resin, forming conducting rubber ambers. The ambers could be further manufactured simply by cutting into any arbitrary 1D, 2D, and 3D shapes, which were all intrinsically conductive without the need of external prewiring, a condition required in the previous aerogel-based conductors. The outstanding electrical conductivity in conjunction with high mechanical compliance enabled prototypes of the elastic piezoresistivity switches and stretchable conductors
Unconventional Janus Properties of Enokitake-like Gold Nanowire Films
We
report on unconventional Janus material properties of vertically
aligned gold nanowire films that conduct electricity and interact
with light and water in drastically different ways on its two opposing
sides. These Janus-like properties originate from enokitake-like nanowire
structures, causing the nanoparticle side (āheadā) to
behave like bulk gold, yet the opposing nanowire side (ātailā)
behaves as discontinuous nanophases. Due to this Janus film structure,
its head side is hydrophilic but its tail side is hydrophobic; its
head side reflects light like bulk gold, yet its tail side is a broadband
superabsorber; its tail side is less conductive but with tunable resistance.
More importantly, the elastomer-bonded Janus film exhibits unusual
mechatronic properties when being stretched, bent, and pressed. The
tail-bonded elastomeric sheet can be stretched up to ā¼800%
strain while remaining conductive, which is about 10-fold that of
head-bonded film. In addition, it is also more sensitive to bending
forces and point loads than the corresponding tail-bonded film. We
further demonstrate the versatility of nanowire-based Janus films
for pressure sensors using bilayer structures in three different assembly
layouts
Unconventional Janus Properties of Enokitake-like Gold Nanowire Films
We
report on unconventional Janus material properties of vertically
aligned gold nanowire films that conduct electricity and interact
with light and water in drastically different ways on its two opposing
sides. These Janus-like properties originate from enokitake-like nanowire
structures, causing the nanoparticle side (āheadā) to
behave like bulk gold, yet the opposing nanowire side (ātailā)
behaves as discontinuous nanophases. Due to this Janus film structure,
its head side is hydrophilic but its tail side is hydrophobic; its
head side reflects light like bulk gold, yet its tail side is a broadband
superabsorber; its tail side is less conductive but with tunable resistance.
More importantly, the elastomer-bonded Janus film exhibits unusual
mechatronic properties when being stretched, bent, and pressed. The
tail-bonded elastomeric sheet can be stretched up to ā¼800%
strain while remaining conductive, which is about 10-fold that of
head-bonded film. In addition, it is also more sensitive to bending
forces and point loads than the corresponding tail-bonded film. We
further demonstrate the versatility of nanowire-based Janus films
for pressure sensors using bilayer structures in three different assembly
layouts