6 research outputs found
Programmable Shape Recovery Process of Water-Responsive Shape-Memory Poly(vinyl alcohol) by Wettability Contrast Strategy
Water-responsive
shape-memory polymers (SMPs) are desirable for
biomedical applications, but their limited shape recovery process
is problematic. Herein, we demonstrate a shape-memory polyÂ(vinyl alcohol)
(SM-PVA) with programmable multistep shape recovery processes in water
via a wettability contrast strategy. A hexamethyldisilazane (HMDS)-treated
SiO<sub>2</sub> nanoparticle layer with varying loading weights was
rationally deposited onto the surface of SM-PVA, aiming to create
surface-wettability contrast. The varying wettability led to different
water adsorption behaviors of SM-PVA that could be well-described
by the pseudo-first-order kinetic model. The results calculated from
the kinetic model showed that both the pseudo-first order-adsorption
rate constant and the saturated water absorption of SM-PVA demonstrated
a declining trend as the loading weight of SiO<sub>2</sub> increased,
which laid the foundation for the local regulation of the water-responsive
rate of SM-PVA. Finally, two proof-of-concept drug-delivery devices
with diverse three-dimensional structures and actuations are presented
based on the water-responsive SM-PVA with preprogrammed multistep
shape recovery processes. We believe the programmable shape-memory
behavior of water-responsive SM-PVA could highly extend its use in
drug delivery, tissue engineering scaffolds, and smart implantable
devices, etc
Room-Temperature Fabrication of High-Performance Amorphous In–Ga–Zn–O/Al<sub>2</sub>O<sub>3</sub> Thin-Film Transistors on Ultrasmooth and Clear Nanopaper
Integrating
biodegradable cellulose nanopaper into oxide thin-film transistors
(TFTs) for next generation flexible and green flat panel displays
has attracted great interest because it offers a viable solution to
address the rapid increase of electronic waste that poses a growing
ecological problem. However, a compromise between device performance
and thermal annealing remains an obstacle for achieving high-performance
nanopaper TFTs. In this study, a high-performance bottom-gate IGZO/Al<sub>2</sub>O<sub>3</sub> TFT with a dual-layer channel structure was
initially fabricated on a highly transparent, clear, and ultrasmooth
nanopaper substrate via conventional physical vapor deposition approaches,
without further thermal annealing processing. Purified nanofibrillated
cellulose with a width of approximately 3.7 nm was used to prepare
nanopaper with excellent optical properties (92% transparency, 0.85%
transmission haze) and superior surface roughness (Rq is 1.8 nm over a 5 × 5 μm<sup>2</sup> scanning area). More significantly, a bilayer channel structure
(IGZO/Al<sub>2</sub>O<sub>3</sub>) was adopted to fabricate high performance
TFT on this nanopaper substrate without thermal annealing and the
device exhibits a saturation mobility of 15.8 cm<sup>2</sup>/(Vs),
an <i>I</i><sub>on</sub>/<i>I</i><sub>off</sub> ratio of 4.4 × 10<sup>5</sup>, a threshold voltage (<i>V</i><sub>th</sub>) of −0.42 V, and a subthreshold swing
(SS) of 0.66 V/dec. The room-temperature fabrication of high-performance
IGZO/Al<sub>2</sub>O<sub>3</sub> TFTs on such nanopaper substrate
without thermal annealing treatment brings industry a step closer
to realizing inexpensive, flexible, lightweight, and green paper displays
Rapid Thermal Annealing of Cathode-Garnet Interface toward High-Temperature Solid State Batteries
High-temperature
batteries require the battery components to be
thermally stable and function properly at high temperatures. Conventional
batteries have high-temperature safety issues such as thermal runaway,
which are mainly attributed to the properties of liquid organic electrolytes
such as low boiling points and high flammability. In this work, we
demonstrate a truly all-solid-state high-temperature battery using
a thermally stable garnet solid-state electrolyte, a lithium metal
anode, and a V<sub>2</sub>O<sub>5</sub> cathode, which can operate
well at 100 °C. To address the high interfacial resistance between
the solid electrolyte and cathode, a rapid thermal annealing method
was developed to melt the cathode and form a continuous contact. The
resulting interfacial resistance of the solid electrolyte and V<sub>2</sub>O<sub>5</sub> cathode was significantly decreased from 2.5
× 10<sup>4</sup> to 71 Ω·cm<sup>2</sup> at room temperature
and from 170 to 31 Ω·cm<sup>2</sup> at 100 °C. Additionally,
the diffusion resistance in the V<sub>2</sub>O<sub>5</sub> cathode
significantly decreased as well. The demonstrated high-temperature
solid-state full cell has an interfacial resistance of 45 Ω·cm<sup>2</sup> and 97% Coulombic efficiency cycling at 100 °C. This
work provides a strategy to develop high-temperature all-solid-state
batteries using garnet solid electrolytes and successfully addresses
the high contact resistance between the V<sub>2</sub>O<sub>5</sub> cathode and garnet solid electrolyte without compromising battery
safety or performance
Superflexible Wood
Flexible
porous membranes have attracted increasing scientific interest due
to their wide applications in flexible electronics, energy storage
devices, sensors, and bioscaffolds. Here, inspired by nature, we develop
a facile and scalable top-down approach for fabricating a superflexible,
biocompatible, biodegradable three-dimensional (3D) porous membrane
directly from natural wood (coded as flexible wood membrane) via a
one-step chemical treatment. The superflexibility is attributed to
both physical and chemical changes of the natural wood, particularly
formation of the wavy structure formed by simple delignification induced
by partial removal of lignin/hemicellulose. The flexible wood membrane,
which inherits its unique 3D porous structure with aligned cellulose
nanofibers, biodegradability, and biocompatibility from natural wood,
combined with the superflexibility imparted by a simple chemical treatment,
holds great potential for a range of applications. As an example,
we demonstrate the application of the flexible, breathable wood membrane
as a 3D bioscaffold for cell growth
Three-Dimensional, Solid-State Mixed Electron–Ion Conductive Framework for Lithium Metal Anode
Solid-state
electrolytes (SSEs) have been widely considered as
enabling materials for the practical application of lithium metal
anodes. However, many problems inhibit the widespread application
of solid state batteries, including the growth of lithium dendrites,
high interfacial resistance, and the inability to operate at high
current density. In this study, we report a three-dimensional (3D)
mixed electron/ion conducting framework (3D-MCF) based on a porous-dense-porous
trilayer garnet electrolyte structure created via tape casting to
facilitate the use of a 3D solid state lithium metal anode. The 3D-MCF
was achieved by a conformal coating of carbon nanotubes (CNTs) on
the porous garnet structure, creating a composite mixed electron/ion
conductor that acts as a 3D host for the lithium metal. The lithium
metal was introduced into the 3D-MCF via slow electrochemical deposition,
forming a 3D lithium metal anode. The slow lithiation leads to improved
contact between the lithium metal anode and garnet electrolyte, resulting
in a low resistance of 25 Ω cm<sup>2</sup>. Additionally, due
to the continuous CNT coating and its seamless contact with the garnet
we observed highly uniform lithium deposition behavior in the porous
garnet structure. With the same local current density, the high surface
area of the porous garnet framework leads to a higher overall areal
current density for stable lithium deposition. An elevated current
density of 1 mA/cm<sup>2</sup> based on the geometric area of the
cell was demonstrated for continuous lithium cycling in symmetric
lithium cells. For battery operation of the trilayer structure, the
lithium can be cycled between the 3D-MCF on one side and the cathode
infused into the porous structure on the opposite side. The 3D-MCF
created by the porous garnet structure and conformal CNT coating provides
a promising direction toward new designs in solid-state lithium metal
batteries
Highly Compressible, Anisotropic Aerogel with Aligned Cellulose Nanofibers
Aerogels
can be used in a broad range of applications such as bioscaffolds,
energy storage devices, sensors, pollutant treatment, and thermal
insulating materials due to their excellent properties including large
surface area, low density, low thermal conductivity, and high porosity.
Here we report a facile and effective top-down approach to fabricate
an anisotropic wood aerogel directly from natural wood by a simple
chemical treatment. The wood aerogel has a layered structure with
anisotropic structural properties due to the destruction of cell walls
by the removal of lignin and hemicellulose. The layered structure
results in the anisotropic wood aerogel having good mechanical compressibility
and fragility resistance, demonstrated by a high reversible compression
of 60% and stress retention of ∼90% after 10 000 compression
cycles. Moreover, the anisotropic structure of the wood aerogel with
curved layers stacking layer-by-layer and aligned cellulose nanofibers
inside each individual layer enables the wood aerogel to have an anisotropic
thermal conductivity with an anisotropy factor of ∼4.3. An
extremely low thermal conductivity of 0.028 W/m·K perpendicular
to the cellulose alignment direction and a thermal conductivity of
0.12 W/m·K along the cellulose alignment direction can be achieved.
The thermal conductivity is not only much lower than that of the natural
wood material (by ∼3.6 times) but also lower than most of the
commercial thermal insulation materials. The top-down approach is
low-cost, scalable, simple, yet effective, representing a promising
direction for the fabrication of high-quality aerogel materials