10 research outputs found
Flexible Conductive Composite Integrated with Personal Earphone for Wireless, Real-Time Monitoring of Electrophysiological Signs
We
introduce optimized elastomeric conductive electrodes using a mixture
of silver nanowires (AgNWs) with carbon nanotubes/polydimethylsiloxane
(CNTs/PDMS), to build a portable earphone type of wearable system
that is designed to enable recording electrophysiological activities
as well as listening to music at the same time. A custom-built, plastic
frame integrated with soft, deformable fabric-based memory foam of
earmuffs facilitates essential electronic components, such as conductive
elastomers, metal strips, signal transducers and a speaker. Such platform
incorporates with accessory cables to attain wireless, real-time monitoring
of electrical potentials whose information can be displayed on a cell
phone during outdoor activities and music appreciation. Careful evaluations
on experimental results reveal that the performance of fabricated
dry electrodes are comparable to that of commercial wet electrodes,
and position-dependent signal behaviors provide a route toward accomplishing
maximized signal quality. This research offers a facile approach for
a wearable healthcare monitor via integration of soft electronic constituents
with personal belongings
Facile Synthesis of Free-Standing Silicon Membranes with Three-Dimensional Nanoarchitecture for Anodes of Lithium Ion Batteries
We propose a facile method for synthesizing
a novel Si membrane
structure with good mechanical strength and three-dimensional (3D)
configuration that is capable of accommodating the large volume changes
associated with lithiation in lithium ion battery applications. The
membrane electrodes demonstrated a reversible charge capacity as high
as 2414 mAh/g after 100 cycles at current density of 0.1 C, maintaining
82.3% of the initial charge capacity. Moreover, the membrane electrodes
showed superiority in function at high current density, indicating
a charge capacity >1220 mAh/g even at 8 C. The high performance
of
the Si membrane anode is assigned to their characteristic 3D features,
which is further supported by mechanical simulation that revealed
the evolution of strain distribution in the membrane during lithiation
reaction. This study could provide a model system for rational and
precise design of the structure and dimensions of Si membrane structures
for use in high-performance lithium ion batteries
Facile Synthesis of Free-Standing Silicon Membranes with Three-Dimensional Nanoarchitecture for Anodes of Lithium Ion Batteries
We propose a facile method for synthesizing
a novel Si membrane
structure with good mechanical strength and three-dimensional (3D)
configuration that is capable of accommodating the large volume changes
associated with lithiation in lithium ion battery applications. The
membrane electrodes demonstrated a reversible charge capacity as high
as 2414 mAh/g after 100 cycles at current density of 0.1 C, maintaining
82.3% of the initial charge capacity. Moreover, the membrane electrodes
showed superiority in function at high current density, indicating
a charge capacity >1220 mAh/g even at 8 C. The high performance
of
the Si membrane anode is assigned to their characteristic 3D features,
which is further supported by mechanical simulation that revealed
the evolution of strain distribution in the membrane during lithiation
reaction. This study could provide a model system for rational and
precise design of the structure and dimensions of Si membrane structures
for use in high-performance lithium ion batteries
Flexible Conductive Composite Integrated with Personal Earphone for Wireless, Real-Time Monitoring of Electrophysiological Signs
We
introduce optimized elastomeric conductive electrodes using a mixture
of silver nanowires (AgNWs) with carbon nanotubes/polydimethylsiloxane
(CNTs/PDMS), to build a portable earphone type of wearable system
that is designed to enable recording electrophysiological activities
as well as listening to music at the same time. A custom-built, plastic
frame integrated with soft, deformable fabric-based memory foam of
earmuffs facilitates essential electronic components, such as conductive
elastomers, metal strips, signal transducers and a speaker. Such platform
incorporates with accessory cables to attain wireless, real-time monitoring
of electrical potentials whose information can be displayed on a cell
phone during outdoor activities and music appreciation. Careful evaluations
on experimental results reveal that the performance of fabricated
dry electrodes are comparable to that of commercial wet electrodes,
and position-dependent signal behaviors provide a route toward accomplishing
maximized signal quality. This research offers a facile approach for
a wearable healthcare monitor via integration of soft electronic constituents
with personal belongings
Synthetic Melanin E‑Ink
Extensive
efforts have been devoted to the development of surfactant-free electronic
ink (E-ink) with excellent display resolution for high-definition
resolution display. Herein, we report the use of polydopamine-based
synthetic melanin, a class of functional nanoparticles with similar
chemical compositions and physical properties to those of naturally
occurring melanin, as a new E-ink material. It was found that such E-ink displays
could achieve ultrahigh resolution (>10 000 ppi) and low
power consumption (operation voltage of only 1 V) in aqueous solutions.
Interestingly, simple oxidation of synthetic melanin nanoparticles
enables the generation of intrinsic fluorescence, allowing further
development of fluorescent E-ink displays with nanoscale resolution.
We describe these bioinspired materials in an initial proof-of-concept
study and propose that synthetic melanin nanoparticles will be suitable
for electronic nanoinks with a potential wide range of applications
in molecular patterning and fluorescence bioimaging
Modulated Degradation of Transient Electronic Devices through Multilayer Silk Fibroin Pockets
The recent introduction
of transient, bioresorbable electronics
into the field of electronic device design offers promise for the
areas of medical implants and environmental monitors, where programmed
loss of function and environmental resorption are advantageous characteristics.
Materials challenges remain, however, in protecting the labile device
components from degradation at faster than desirable rates. Here we
introduce an indirect passivation strategy for transient electronic
devices that consists of encapsulation in multiple air pockets fabricated
from silk fibroin. This approach is investigated through the properties
of silk as a diffusional barrier to water penetration, coupled with
the degradation of magnesium-based devices in humid air. Finally,
silk pockets are demonstrated to be useful for controlled modulation
of device lifetime. This approach may provide additional future opportunities
for silk utility due to the low immunogenicity of the material and
its ability to stabilize labile biotherapeutic dopants
Dissolution Chemistry and Biocompatibility of Silicon- and Germanium-Based Semiconductors for Transient Electronics
Semiconducting
materials are central to the development of high-performance electronics
that are capable of dissolving completely when immersed in aqueous
solutions, groundwater, or biofluids, for applications in temporary
biomedical implants, environmentally degradable sensors, and other
systems. The results reported here include comprehensive studies of
the dissolution by hydrolysis of polycrystalline silicon, amorphous
silicon, silicon–germanium, and germanium in aqueous solutions
of various pH values and temperatures. In vitro cellular toxicity
evaluations demonstrate the biocompatibility of the materials and
end products of dissolution, thereby supporting their potential for
use in biodegradable electronics. A fully dissolvable thin-film solar
cell illustrates the ability to integrate these semiconductors into
functional systems
Biodegradable Elastomers and Silicon Nanomembranes/Nanoribbons for Stretchable, Transient Electronics, and Biosensors
Transient
electronics represents an emerging class of technology that exploits
materials and/or device constructs that are capable of physically
disappearing or disintegrating in a controlled manner at programmed
rates or times. Inorganic semiconductor nanomaterials such as silicon
nanomembranes/nanoribbons provide attractive choices for active elements
in transistors, diodes and other essential components of overall systems
that dissolve completely by hydrolysis in biofluids or groundwater.
We describe here materials, mechanics, and design layouts to achieve
this type of technology in stretchable configurations with biodegradable
elastomers for substrate/encapsulation layers. Experimental and theoretical
results illuminate the mechanical properties under large strain deformation.
Circuit characterization of complementary metal-oxide-semiconductor
inverters and individual transistors under various levels of applied
loads validates the design strategies. Examples of biosensors demonstrate
possibilities for stretchable, transient devices in biomedical applications
Si/Ge Double-Layered Nanotube Array as a Lithium Ion Battery Anode
Problems related to tremendous volume changes associated with cycling and the low electron conductivity and ion diffusivity of Si represent major obstacles to its use in high-capacity anodes for lithium ion batteries. We have developed a group IVA based nanotube heterostructure array, consisting of a high-capacity Si inner layer and a highly conductive Ge outer layer, to yield both favorable mechanics and kinetics in battery applications. This type of Si/Ge double-layered nanotube array electrode exhibits improved electrochemical performances over the analogous homogeneous Si system, including stable capacity retention (85% after 50 cycles) and doubled capacity at a 3<i>C</i> rate. These results stem from reduced maximum hoop strain in the nanotubes, supported by theoretical mechanics modeling, and lowered activation energy barrier for Li diffusion. This electrode technology creates opportunities in the development of group IVA nanotube heterostructures for next generation lithium ion batteries
Dissolution Chemistry and Biocompatibility of Single-Crystalline Silicon Nanomembranes and Associated Materials for Transient Electronics
Single-crystalline silicon nanomembranes (Si NMs) represent a critically important class of material for high-performance forms of electronics that are capable of complete, controlled dissolution when immersed in water and/or biofluids, sometimes referred to as a type of “transient” electronics. The results reported here include the kinetics of hydrolysis of Si NMs in biofluids and various aqueous solutions through a range of relevant pH values, ionic concentrations and temperatures, and dependence on dopant types and concentrations. <i>In vitro</i> and <i>in vivo</i> investigations of Si NMs and other transient electronic materials demonstrate biocompatibility and bioresorption, thereby suggesting potential for envisioned applications in active, biodegradable electronic implants