Recently, flexible textile-based
sensors have drawn great interest
due to their promising application in wearable electronics. However,
most previous work has been done either by attaching conventional
sensors to a textile-based substrate or by sewing fiber-like sensors
into fabrics. The use of an additional substrate would interfere with
detection performance and to some extent reduce user experience. Herein,
we propose a flexible, freestanding tactile sensor by using the MXene/cotton
composite thread as electronic electrodes and ionic gel (IG) as an
iontronic electrolyte. Two or more such fiber electrodes are crisscross
placed and bonded with a small amount of IG as glue at the intersection
points to form the sensor unit or array without using any substrate.
Due to its supercapacitive sensing mechanism upon optimization of
electrode thickness and IG composition, it shows a high sensitivity
of 9.62 kPa–1 (0–40 kPa), ultralow detection
limit of 0.884 Pa, and short response time of 24 ms. The sensor is
capable of detecting micromotions like pulse beat at the wrist, water
dripping, and sound wave through the air. In addition, a 6 ×
6 sensor array is demonstrated to acquire 2D pressure mapping with
recognition of different object shapes. Moreover, the sensor array
can be conformally attached on a complex surface of 3D objects such
as a table tennis ball to detect 3D positioned pressures. The proposed
tactile-sensing textile in the true sense would provide a concept
to develop advanced sensing devices with comfort for wearable systems.
The continuous real-time monitoring of human physical health is crucial in the pursuit in a high quality of modern life and has attracted a great deal of attention in research on advanced wearable pressure sensors. However, most of the previous sensors have been built on flexible solid substrate that is not air permeable, leading to skin inflammation after a long-term skin attachment. Herein, we have developed a flexible and breathable pressure sensor based on nonwoven fabrics decorated with MXene as fabric electrodes and an ionic gel as a fabric electrolyte. Due to the advantages of both the supercapacitive iontronic sensing mechanism and the hierarchical structures of the nanoscaled stacked MXene wrapping on the microscale fabric framework, the optimized pressure sensor exhibits a high sensitivity of 31.40 kPa −1 (0−10 kPa), a wide detection range of up to 80 kPa, and a short response time of ∼45 ms as well as excellent repeatability and cyclability. The fabric sensor can be seamlessly woven into textiles for practical wearable sensing and is capable of detecting subtle arterial pulse beats at the wrist and weak breathing rhythms at the chest without affecting the comfort of the wearer. The incorporation of the developed fabric sensors into commonly used clothing through a facile manufacturing process is promising to achieve a comfortable health diagnosis.
Hybrid
energy devices combining multiple energy components based
on different mechanisms can provide a more comprehensive output performance
than individual ones. However, past attempts of connecting separate
parts through additional wire connections have limitations of low
energy efficiency and bulky system formation. Herein, we develop a
hybrid energy device that integrates a rechargeable zinc-air battery
and an asymmetric supercapacitor on a single carbon-cloth-based platform.
Nanostructured Co3O4 is asymmetrically deposited
in different regions of the carbon cloth to obtain bi-functions as
pseudocapacitive positive electrode and catalytic air electrode. A
moisturizing gel polymer electrolyte is also used to make the device
integrative, compact, and flexible. A working mechanism and an operation
strategy of repeated in situ charging of the supercapacitor part by
the zinc-air battery part and external recharging of the zinc-air
battery part are proposed and evaluated with demonstration of powering
a vibration motor. The developed hybrid energy device can be self-charged
to 1.15 V in 200 s followed by delivering a peak power density of
7.91 mW cm–2 for 50 repeated cycles and be fully
recharged by an external power source again. Thus, both zinc-air high-energy
conversion and asymmetric supercapacitive high-power delivery are
simultaneously achieved on such a single device, which has a potential
use in portable and wearable electronic applications.
Lightweight, compact, integrated, and miniaturized energy
devices
are under high pursuit for portable and wearable electronics. However,
improving the energy density per area still remains a long-standing
challenge. Herein, we report the design and fabrication of a solid-state
zinc-air microbattery (ZAmB) by a facile 3D direct printing technique.
The interdigital electrodes, gel electrolyte, and encapsulation frame
are all printed with a customized design by optimzing the composition
of the printing inks to obtain the best battery performance. Multiple
layers of interdigital electrodes are sequentially printed with a
fine overlap to achieve an ultrahigh thickness of 2.5 mm for a remarkably
increased specific areal energy of up to 77.2 mWh cm–2. To meet the practical powering requirements for different output
voltages and currents, battery modules consisting of individual ZAmBs
connected in series or parallel or a combination of the two are printed
with a facile integration to external loads. Powering of LEDs, digital
watch, and a miniature rotary motor and even charging of a smartphone
by the printed ZAmB modules are successfully demonstrated. The versatile
3D direct printing technique enables the fabricated ZAmBs with an
adjustable form factor and integration capability with other electronics,
paving the way for exploring new energy systems with diverse structures
and extended functionalities.
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