Inspired by the turbinate
structure in the olfaction system of
a dog, a biomimetic artificial nose based on 3D porous laser-induced
graphene (LIG) decorated with palladium (Pd) nanoparticles (NPs) has
been developed for room-temperature hydrogen (H2) detection.
A 3D porous biomimetic turbinate-like network of graphene was synthesized
by simply irradiating an infrared laser beam onto a polyimide substrate,
which could further be transferred onto another flexible substrate
such as polyethylene terephthalate (PET) to broaden its application.
The sensing mechanism is based on the catalytic effect of the Pd NPs
on the crystal defect of the biomimetic LIG turbinate-like microstructure,
which allows facile adsorption and desorption of the nonpolar H2 molecules. The sensor demonstrated an approximately linear
sensing response to H2 concentration. Compared to chemical
vapor-deposited (CVD) graphene-based gas sensors, the biomimetic turbinate-like
microstructure LIG-gas sensor showed ∼1 time higher sensing
performance with much simpler and lower-cost fabrication. Furthermore,
to expand the potential applications of the biomimetic sensor, we
modulated the resistance of the biomimetic LIG sensor by varying laser
sweeping gaps and also demonstrated a well-transferred LIG layer onto
transparent substrates. Moreover, the LIG sensor showed good mechanical
flexibility and robustness for potential wearable and flexible device
applications.
High-performance,
monolithic photoactivated gas sensors based on the integration of
gas-sensitive semiconductor metal oxide nanowires on micro light-emitting
diodes (μLEDs) are introduced. The μLEDs showed improved
irradiance and energy conversion efficiency (i.e., external quantum
efficiency, EQE), as the size of LEDs was reduced from 200 ×
200 μm2 (irradiance of 46.5 W/cm2 and
EQE of 4%) to 30 × 30 μm2 (irradiance of 822.4
W/cm2 and EQE of 9%). Gas-sensitive zinc oxide (ZnO) nanowires
were directly synthesized on top of the μLED through a hydrothermal
reaction. The direct contact between the sensing component and μLED
sensor platform leads to high light coupling efficiency, minimizing
power consumption of the sensor. Furthermore, the sensing performance
(i.e., sensitivity) at optimal operating power was improved as the
LED size was reduced. The smallest fabricated gas sensor (active area
= 30 × 30 μm2) showed excellent NO2 sensitivity (ΔR/R
0 = 605% to 1 ppm NO2) at the optimal operating power (∼184
μW). In addition, the sensor showed a low limit of detection
(∼14.9 ppb) and robustness to high humidity conditions, which
demonstrate its potential for practical applications in mobile internet
of things (IoT) devices.
A hydrogen (H ) gas sensor based on a silicon (Si) nanomesh structure decorated with palladium (Pd) nanoparticles is fabricated via polystyrene nanosphere lithography and top-down fabrication processes. The gas sensor shows dramatically improved H gas sensitivity compared with an Si thin film sensor without nanopatterns. Furthermore, a buffered oxide etchant treatment of the Si nanomesh structure results in an additional performance improvement. The final sensor device shows fast H response and high selectivity to H gas among other gases. The sensing performance is stable and shows repeatable responses in both dry and high humidity ambient environments. The sensor also shows high stability without noticeable performance degradation after one month. This approach allows the facile fabrication of high performance H sensors via a cost-effective, complementary metal-oxide-semiconductor (CMOS) compatible, and scalable nanopatterning method.
This paper reports zinc oxide (ZnO)-coated piezoelectret polypropylene (PP) microfibers with a structure of two opposite arc-shaped braces for enhanced mechanical energy harvesting. The ZnO film was coated onto PP microfibers via magnetron sputtering to form a ZnO/PP compound structure. Triboelectric Nanogenerator (TENG) based on ZnO/PP microfiber compound film was carefully designed with two opposite arc-shaped braces. The results of this study demonstrated that the mechanical energy collection efficiency of TENG based on piezoelectret PP microfiber was greatly enhanced by the coated ZnO and high-voltage corona charging method. We found that, with the step-increased distance of traveling for the movable carbon black electrode, an electrical power with an approximately quadratic function of distance was generated by this mechanical-electrical energy conversion, because more PP microfibers were connected to the electrode. Further, with a full contact condition, the peak of the generated voltage, current, and charges based on the ZnO/PP microfibers by this mechanical-electrical energy conversion with 1 m/s reached 120 V, 3 μA, and 49 nC, respectively. Moreover, a finger-tapping test was used to demonstrate that the ZnO/PP microfiber TENG is capable of lighting eight light-emitting diodes.
High-performance and low-power flexible Schottky diode-based hydrogen sensor was developed. The sensor was fabricated by releasing Si nanomembrane (SiNM) and transferring onto a plastic substrate. After the transfer, palladium (Pd) and aluminum (Al) were selectively deposited as a sensing material and an electrode, respectively. The top-down fabrication process of flexible Pd/SiNM diode H sensor is facile compared to other existing bottom-up fabricated flexible gas sensors while showing excellent H sensitivity (Δ I/ I > 700-0.5% H concentrations) and fast response time (τ = 22 s) at room temperature. In addition, selectivity, humidity, and mechanical tests verify that the sensor has excellent reliability and robustness under various environments. The operating power consumption of the sensor is only in the nanowatt range, which indicates its potential applications in low-power portable and wearable electronics.
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