Terahertz Metamaterial-Based Microbolometers Fabricated by Conventional MEMS

37 μm × 37 μm array of metamaterial-based microbolometers was designed and successfully fa-bricated by conventional MEMS technology. FTIR measurements reveal that the as-designed mi-crobolometers exhibit a high absorption of ~31.5% at 3.93 THz. In contrast, no response can be detected from those microbolometers without metamaterials. The experimental results have been confirmed by simulations.

One-pot preparation and applications of self-healing,self-adhesive PAA-PDMS elastomers

A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethylsiloxane(PDMSOH).The condensation reaction between PAA and PDMS-OH has been confirmed by attenuated total reflection Fourier transform infrared(ATR-FTIR)spectra.The prepared PAA-PDMS elastomers possess robust mechanical strength and strong adhesiveness to human skin,and they have fast self-healing ability at room temperature(in^10 s with the efficiency of 98%).Specifically,strain sensors were fabricated by assembling PAA-PDMS as packaging layers and polyetherimide-reduced graphene oxide(PEI-rGO)as strain-sensing layers.The PAA-PDMS/PEI-rGO sensors are stably and reliably responsive to slight physical deformations,and they can be attached onto skin directly to monitor the body’s motions.Meanwhile,strain sensors can self-heal quickly and completely,and they can be reused for the motion detecting after shallowly scratching the surface.This work provides new opportunities to manufacture high performance self-adhesive and self-healing materials.

Vapor Phase Polymerization Deposition Conducting Polymer Nanocomposites on Porous Dielectric Surface as High Performance Electrode Materials

We report chemical vapor phase polymerization(VPP) deposition of poly(3,4-ethylenedioxythiophene)(PEDOT) and PEDOT/graphene on porous dielectric tantalum pentoxide(Ta_2O_5) surface as cathode films for solid tantalum electrolyte capacitors. The modified oxidant/oxidant-graphene films were first deposited on Ta_2O_5 by dip-coating, and VPP process was subsequently utilized to transfer oxidant/oxidant-graphene into PEDOT/PEDOT-graphene films. The SEM images showed PEDOT/PEDOT-graphene films was successfully constructed on porous Ta_2O_5 surface through VPP deposition, and a solid tantalum electrolyte capacitor with conducting polymer-graphene nano-composites as cathode films was constructed. The high conductivity nature of PEDOT-graphene leads to resistance decrease of cathode films and lower contact resistance between PEDOT/graphene and carbon paste. This nano-composite cathode films based capacitor showed ultralow equivalent series resistance(ESR) ca. 12 m? and exhibited excellent capacitance-frequency performance, which can keep 82% of initial capacitance at 500 KHz. The investigation on leakage current revealed that the device encapsulation process has no influence on capacitor leakage current, indicating the excellent mechanical strength of PEDOT/PEDOT-gaphene films. This high conductivity and mechanical strength of graphene-based polymer films shows promising future for electrode materials such as capacitors, organic solar cells and electrochemical energy storage devices.

Study on ChemFET NO_2 Gas Sensor Array

Based on conventional metal-oxide-semiconductor field-effect transistor (MOSFET),a novel kind of chemical field-effect transistor (ChemFET) gas sensor array has been designed and fabricated.The obtained sensor consists of self-assembly polyaniline (PAN) composite film containing poly(acrylic acid) (PAA) which was used as gate material of MOSFET instead of conventional metallic gate.The UV-Vis absorption spectra of PAN/PAA films were characterized.The NO_2 gas sensitive property of the ChemFET sensor array was also investigated.Results show that the drain current of devices increases with increasing of back-side voltage,and decreases with the increase of NO_2 concentration when the NO_2 concentration is below 20μg/g.The temperature dependence of ChemFET sensor array shows that the drain current of ChemFET sensor decreases with increasing of temperature.

Electronic Textile with Passive Thermal Management for Outdoor Health Monitoring

Soft and wearable electronics for monitoring health in hot outdoor environments are highly desirable due to their effective-ness in safeguarding individuals against escalating heat-related illnesses associated with global climate change.However,traditional wearable devices have limitations when exposed to outdoor solar radiation,including reduced electrical perfor-mance,shortened lifespan,and the risk of skin burns.In this work,we introduce a novel approach known as the cooling E-textile(CET),which ensures reliable and accurate tracking of uninterrupted physiological signals in intense external conditions while maintaining the device at a consistently cool temperature.Through a co-designed architecture comprising a spectrally selective passive cooling structure and intricate hierarchical sensing construction,the monolithic integrated CET demonstrates superior sensitivity(6.67×10^(3)kPa^(-1)),remarkable stability,and excellent wearable properties,such as flexibility,lightweightness,and thermal comfort,while achieving maximum temperature reduction of 21°C.In contrast to the limitations faced by existing devices that offer low signal quality during overheating,CET presents accurately stable performance output even in rugged external environments.This work presents an innovative method for effective thermal management in next-generation textile electronics tailored for outdoor applications.

MXene复合气敏材料:进展与未来挑战

过渡金属碳/氮化物(transition metal carbon/nitrides,MXenes)作为一类新兴的二维材料,由于其独特的层状结构、可调的电学特性与丰富的终端基团,在传感、储能及电磁屏蔽等领域得到研究者的极大关注.近年来,MXenes基气体传感器被广泛研究与报道.本综述聚焦于MXenes及其复合材料在气敏领域的研究现状与最新进展,从以下3个方面进行概括:(1)MXenes的基本情况,主要包括结构、分类与特性;(2)MXenes的制备方法,包括典型的氢氟酸刻蚀法、插层工艺以及无氟刻蚀法;(3)MXenes及其复合材料基气体传感器.根据检测对象主要分为氨气(ammonia,NH_(3))、二氧化氮(nitrogen dioxide,NO_(2))与挥发性有机物(volatile organic compounds,VOCs)气体传感器.最后,本文对MXenes及其复合材料在气敏应用领域所面临的问题与挑战进行了总结与讨论,并对其未来的发展方向进行展望.

Gas sensors for CO_2 detection based on RGO–PEI films at room temperature

In this paper,polyethyleneimine(PEI)and reduced graphene oxide(RGO)were selected as sensing materials for carbon dioxide detection.Two kinds of sensors with different sensitive film structures,i.e.,RGO–PEI composite film and RGO–PEI bi-layer film were fabricated by airbrushing the sensitive films on interdigitated electrodes.Response performances of both sensors at room temperature were investigated.Results showed that sensors with bi-layer film exhibited smaller baseline drift and more stable sensing characteristics than the counterparts with composite film.Furthermore,bi-layer film sensors with different quantity of PEI solution deposited were studied.Performances of long-time stability,repeatability,low concentration of detection for carbon dioxide,and measurements of response time and recovery time were investigated.It was found that appropriate weight ratio of RGO and PEI was critical for sensing response.In addition,the sensor with bi-layer film exhibited a better repeatability but had longer response time and recovery time than RGO single-layer sensor,and both of them could detect as low as20 parts per million carbon dioxide gas.Sensing responses of the prepared sensors to carbon dioxide under dry air or nitrogen were compared.The relevant sensing mechanisms were studied as well.

Controllable resistive switching of STO:Ag/SiO2-based memristor synapse for neuromorphic computing

Resistive random-access memory(RRAM)is a promising technology to develop nonvolatile memory and artificial synaptic devices for brain-inspired neuromorphic computing.Here,we have developed a STO:Ag/SiO_(2) bilayer based memristor that has exhibited a filamentary resistive switching with stable endurance and long-term data retention ability.The memristor also exhibits a tunable resistance modulation under positive and negative pulse trains,which could fully mimic the potentiation and depression behavior like a bio-synapse.Several synaptic plasticity functions,including long-term potentiation(LTP)and long-term depression(LTD),paired-pulsed facilitation(PPF),spike-rate-dependent-plasticity(SRDP),and post-tetanic potentiation(PTP),are faithfully implemented with the fabricated memristor.Moreover,to demonstrate the feasibility of our memristor synapse for neuromorphic applications,spike-timedependent plasticity(STDP)is also investigated.Based on conductive atomic force microscopy observations and electrical transport model analyses,it can be concluded that it is the controlled formation and rupture of Ag filaments that are responsible for the resistive switching while exhibiting a switching ratio of~10;along with a good endurance and stability suitable for nonvolatile memory applications.Before fully electroforming,the gradual conductance modulation of Ag/STO:Ag/SiO_(2)/p^(++)-Si memristor can be realized,and the working mechanism could be explained by the succeeding growth and contraction of Ag filaments promoted by a redox reaction.This newly fabricated memristor may enable the development of nonvolatile memory and realize controllable resistance/weight modulation when applied as an artificial synapse for neuromorphic computing.

High performance ethylene sensor based on palladium-loaded tin oxide:Application in fruit quality detection

Ethylene(C2 H4),as a plant hormone,its emission can be served as an indicator to measure fruit quality.Due to the limited physiochemical reactivity of C2 H4,it is a challenge to develop high performance C2 H4 sensors for fruit detection.Herein,this paper presents a resistive-type C2 H4 sensor based on Pd-loaded tin oxide(SnO2).The C2 H4 sensing performance of proposed sensor are tested at optimum operating temperature(250℃)with ambient relative humidity(51.9%RH).The results show that the response of Pd-loaded SnO2 sensor(11.1,Ra/Rg)is about 3 times higher than that of pristine SnO2(3.5)for 100 ppm C2 H4.The response time is also significantly shortened from 7 s to 1 s compared with pristine SnO2.Especially,the Pd-loaded SnO2 sensor possesses good sensitivity(0.58 ppm 1)at low concentration(0.05-1 ppm)with excellent linearity(R2=0.9963)and low detection limit(50 ppb).The high sensing performance of Pd-loaded SnO2 are attributed to the excellent adsorption and catalysis effects of Pd nanoparticle.Meaningfully,the potential applications of C2 H4 sensor are performed for monitoring the maturity and freshness of fruits,which presents a promising prospect in fruit quality evaluation.

Preparation and Characterization of LiTaO_3 Films Derived by an Improved Sol-Gel Process

In this paper, an improved sol-gel method was suggested to obtain high-concentration LiTaO3 precursor solution for simplified experimental conditions and thicker films, by mixing lithium acetate and tantalum ethoxide in a 1, 2-Propylene glycol solution. Compared to traditional methods, the process was done without weak acidic solution and absolute dry experimental condition. Results of a comparative study of LiTaO3 thin films derived by the improved sol-gel process and a traditional process using 2-methoxy ethanol as solvent were presented. Nano-crystalline LiTaO3 films with rhombohedral structures were formed in both methods after annealing at 650℃ for 5 min. The thickness of each LiTaO3 layer coated onto the substrate increased from 25 nm to 110 nm when 2-methoxy ethanol was replaced by 1, 2-Propylene glycol. LiTaO3 films with a stronger preferential orientation were obtained in 1, 2-Propylene glycol due to its higher boiling point and slower volatilization rate. On the other hand, the diffraction peak intensity of LiTaO3 thin films prepared using 1, 2-Propylene glycol was weaker than that of the films prepared using 2-methoxy ethanol due to decreased times of annealing.

Detection of 2,4-dinitrotoluene using hydrogen-bond acidic polymer coated SAW sensor

A strong hydrogen-bond acidic(HBA)polymer linear fluoroalcoholic polysiloxane(PLF),synthesized by one-step hydrosilylation,was introduced for 2,4-dinitrotoluene(2,4-DNT)detection using surface acoustic wave(SAW)devices.FT-IR spectra and1H NMR spectra characterizations confirmed its molecular structure.Then,PLF was dissolved in chloroform,and spray coated onto a434 MHz SAW device.And subsequently,the sensitivity and selectivity of the fabricated sensor were studied based on a SAW test platform.To 2,4-DNT of 1 ppm and 100 ppb(for DNT,1 ppm=8.1 mg/m3;1 ppb=8.1 lg/m3),the responses of the sensor rose 7.7 and 1.5 kHz,respectively.Furthermore,compared with some common interference vapors at 10 mg/m3,the response of the sensor to 2,4-DNT at1 ppm was 5 times stronger.The sensitive property was attributed to the hydrogen bond interaction between the hexafluoroisopropanol(HFIP)group in PLF and the basic lone electron pairs of nitro-groups in 2,4-DNT.Comparison between the PLF sensor and hydroxyl group functionalized polymer(carbowax and MOBCD)-coated sensors was investigated,and the results showed that the PLF sensor exhibited better sensitivity.In a word,the PLF sensor exhibited fast response,negligible baseline drifts and excellent reversibility,indicating good candidates of HFIP group functionalized HBA polymers for practical nitroaromatic explosives detection.

An oxide-based heterojunction optoelectronic synaptic device with wideband and rapid response performance

With the rapid development of science and technology,the emergence of new application scenarios,such as robots,driverless vehicles and smart city,puts forward high requirements for artificial visual systems.Optoelectronic synaptic devices have attracted much attention due to their advantages in sensing,memory and computing integration.In this work,via band structure engineering and heterostructure designing,a heterojunction optoelectronic synaptic device based on Cu doped with n-type SrTiO_(3)(Cu:STO)film combined with p-type CuAlO_(2)(CAO)thin film was fabricated.It is found surprisingly that the optoelectronic device based on Cu:STO/CAO p-n heterojunction exhibits a rapid response of 2 ms,and that it has a wideband response from visible to near-infrared(NIR)region.Additionally,a series of important synaptic functions,including excitatory postsynaptic current(EPSC),paired-pulse facilitation(PPF),shortterm potentiation(STP)to long-term potentiation(LTP)transition,learning experience behavior and image sharpening,have been successfully simulated on the device.More importantly,the performance of the device remains still stable and reliable after several months which were stored at room temperature and atmospheric pressure.Based on these advantages,the optoelectronic synaptic devices demonstrated here provide great potential in the new generation of artificial visual systems.

Light response and adsorption interaction of black phosphorus quantum dots and single‑layer graphene phototransistor

Black phosphorus quantum dots(BPQDs)are synthesized and combined with graphene sheet.The fabricated BPQDs/graphene devices are capable of detecting visible and near infrared radiation.The adsorption efect of BPQDs in graphene is clarifed by the relationship of the photocurrent and the shift of the Dirac point with diferent substrate.The Dirac point moves toward a neutral point under illumination with both SiO_(2)/Si and Si(3)N_(4)/Si substrates,indicating an anti-doped feature of photo-excitation.To our knowledge,this provides the frst observation of photoresist induced photocurrent in such systems.Without the infuence of the photoresist the device can respond to infrared light up to 980 nm wavelength in vacuum in a cryostat,in which the photocurrent is positive and photoconduction efect is believed to dominate the photocurrent.Finally,the adsorption efect is modeled using a frst-principle method to give a picture of charge transfer and orbital contribution in the interaction of phosphorus atoms and single-layer graphene.

Enhancement of open circuit voltage in organic solar cells by doping a fluorescent red dye

The open circuit voltage （Voc） of small- molecule organic solar cells （OSCs） could be improved by doping suitable fluorescent dyes into the donor layers. In this paper, 4-（dicyanomethylene）-2-t-butyl-6-（1,1,7,7- tetramethyljulolidyl-9-enyl）-4H-pyran （DCJTB） was used as a dopant, and the performance of the OSCs with different DCJTB concentration in copper phthalocyanine （CuPc） was studied. The results showed that the Voc of the OSC with 50% of DCJTB in CuPc increased by 15%, compared with that of the standard CuPc/fullerene （C60） device. The enhancement of the Voc was attributed to the lower highest occupied molecular orbital （HOMO） level in the DCJTB than that in the CuPc. Also, the light absorption intensity is enhanced between 400 and 550nm, where CuPc and C6o have low absorbance, leading to a broad absorption spectrum.