A Simple Graphene NH₃ Gas Sensor via Laser Direct Writing.

Ammonia gas sensors are very essential in many industries and everyday life. However, their complicated fabrication process, severe environmental fabrication requirements and desorption of residual ammonia molecules result in high cost and hinder their market acceptance. Here, laser direct writing is used to fabricate three parallel porous 3D graphene lines on a polyimide (PI) tape to simply construct an ammonia gas sensor. The middle one works as an ammonia sensing element and the other two on both sides work as heaters to improve the desorption performance of the sensing element to ammonia gas molecules. The graphene lines were characterized by scanning electron microscopy and Raman spectroscopy. The response and recovery time of the sensor without heating are 214 s and 222 s with a sensitivity of 0.087% ppm-1 for sensing 75 ppm ammonia gas, respectively. The experimental results prove that under the optimized heating temperature of about 70 °C the heaters successfully help implement complete desorption of residual NH₃ showing a good sensitivity and cyclic stability

NanoGetters for MEMS Hermetic Packaging

A new getter, we call it nanogetter, based on carbon nanotubes (CNTs) coated Ti films has been developed with the purpose of providing a more efficient material, capable of getting active at high vacuum environment (< 10(-3)Torr, molecular state) and low temperature (<400 degrees C). Because of the large surface area of CNTs and its native gas adsorption ability, dense CNTs growth on silicon substrate is considered to be an effective skeleton structure of the nanogetters. All the tests have demonstrated that surface area of nanogetters do have been increased and the pumping speed is enhanced to large amount compared with some traditional getters, such as St175 of SAES in Italy

Electrospun Nanofibrous Membrane for Air Filtration

Nanofibers have a large potential in air filtration applications, so this paper explores the performance of electrospun nanofiber membrane compared to traditional filtration fabrics. Poly (ethylene oxide) (PEO) and Polyvinyl Alcohol (PVA) were electrospun into nanofibrous membranes and analyzed their filtration attributes. Experimentation revealed that nanofibrous membranes have higher filtration efficiency than traditional filtration fabrics, such as meltblown and needle filtration material. In addition, Nanofibrous membranes under the same electrospinning process but with different materials had similar high filtration efficiency, while their permeability had obvious difference. We suggest that different structure in the nanofiber membrane should cause this difference. Our work proves that there is a large potential for nanofiber membranes to utilize in air filtration area

Chemiresistive Nanosensors with Convex/Concave structures

航空航天学院陈松月副教授和化学化工学院、物理科学与技术学院双聘教授侯旭共同在国际著名期刊Nano Today (纳米科学领域权威刊物，IF=17.476)上发表了该文章。随着纳米技术和新材料的涌现，纳米传感器自90年代末出现后，因其高比表面积带来的优越性受到了越来越多的研究上和应用上的关注。本论文综述了基于一维结构（特殊凹凸结构）的化学电阻式纳米传感器，包括纳米线、纳米管和纳米孔道结构。根据传感器的不同材料和结构，分别讨论了它们的传感原理、材料和结构设计、界面设计、在不同领域中的应用。在此基础上讨论了各种纳米传感器在应用中表现出的优缺点。并提出了未来的发展将更注重传感器的稳定性、灵敏度、特异性以及器件的可集成性。【Abstract】Nanosensors have attracted tremendous, scientific and application, interests promoted by the advances in nanotechnology and emerging new nanomaterials. There has been rapid progress in developing chemiresistive nanosensors, and these sensor technologies are being transferred among a variety of different fields, from energy, environment to life science. This review presents nanomaterials with special convex/concave structures used for chemiresistive sensors, which mainly composed of one-dimensional conductive structures, e.g. nanowires, nanotubes, nanopores and nanochannels. Furthermore, designing, operation, and applications of current chemiresistive nanosensors are discussed to give an outlook of this field, especially for ionic solution and gas as the working chemical environments. The authors hope this review could inspire the active interest in the scientific field of sensor development and application.This work was supported by the National Natural Science Foundation of China (grant numbers 61601387, 21673197, U1505243), the Natural Science Foundation of Fujian Province of China (grant number 2017J05107), Young Overseas High-level Talents Introduction Plan, the 111 Project (grant number B16029), the Open Funding of State Key Laboratory of Precision Measuring Technology and Instruments (grant number pilab1709), and the Fundamental Research Funds for the Central Universities of China (grant number 20720170050). 该工作得到了国家自然科学基金（项目批准号: 61601387, 21673197, U1505243），福建省自然科学基金（项目批准号: 2017J05107），高等学校学科创新引智计划（项目批准号: B16029），精密测试技术及仪器国家重点实验室开放基金（项目批准号: pilab1709）和厦门大学校长基金（项目批准号: 20720170050）等资助与支持

3D-printed membrane microvalves and microdecoder

Abstract(#br)A microfluidic system for multichannel switching and multiphase flow control has potential uses in pneumatic soft robotics and biological sampling systems. At present, the membrane microvalves used in microfluidic systems are mostly constructed using a multilayer bonding process so that the device cannot withstand high pressures. In this paper, we demonstrate a design method and the properties of a bondless membrane microvalve fabricated using a commercial 3D printer. We used a multijet (MJP) 3D printer to print a 100-μm-thick and 6-mm-diameter membrane from a relatively hard material (1700 MPa). The membrane’s high toughness ensures that it does not need negative pressure to reopen. The measured operation frequency was less than 2.5 Hz under a pneumatic pressure of 14.5 kPa...

Needleless Electrospinning of Multiple Nanofibers

To satisfy the increasing applications of the electrospun nanofibers, a novel method for the high throughput nanofibers electrospinning which is called "Needleless ElectroSpinning (NES)" is presented in the article. Instead of using the conventional needle, ElectroHydroDynamics (EHD) instabilities mechanism on the electrified liquid film free surface forms the foundation of the NES process, in which, we use a metal cylindrical rotator with smooth or tipped surface as the spinneret electrode, and the production rate of nanofibers can be controlled by adjusting the length and diameter of cylindrical rotator. The main factor such as solution concentration, the diameter of cylindrical rotator, the distance between the rotator and the grounded collector and so on are investigated in our experiment. Results show that solid nanofibers with diameter of 100nm-800nm can be electrospun onto metal substrate with electrode-to-substrate distance of 10-20cm under bias of 40-70 kV. Compared with the conventional electrospinning method, the yield is expected to be increased by more than 125 times

Studies on MEMS vacuum sensor based on field emission of silicon tips array

In this paper, we present our recent works on the fabrication and testing of a novel MEMS (micro electro mechanical systems) vacuum sensor based on field emission of silicon tips array. The prototype vacuum sensor had been fabricated and tested under some conditions. It worked as a diode, having the voltage as the input and field emission current as output, with threshold voltage of approximate 7V and breakdown voltage of about 265V. When the pressure fell from 0.037Pa to 0.0077Pa, the field emission current increased from 80.3 mu A to 96.3 mu A. This work suggests a potential application of field emission to vacuum sensor

Electrospun nanofibers bundles

Aligned nanofibers, filament bundle composed of large number of nanofibers have potential applications such as biomaterials, composite materials etc. A series of electrospinning experiment has been conducted to investigate the electrospinning process, through which, some parameters such as polymer solution concentration, bias voltage, distance between spinneret and collector, solution flow rate etc have been setup to do the experiment of nanofibers bundles construction. This work firstly reports electrospun nanofibers bundles through non-uniform electrical field, and nanofibers distributed with different density on electrodes from that between them. Thinner nanofibers bundle with a few numbers of nanofiber is collected for 3 seconds; therefore it's also possible that the arldressable single nanofiber could be collected bridging the two electrodes

Etch-back in DDSOG Process by Ultrasonic Agitation and Application to Tunneling Gyroscope Fabrication

The etch-back of anodic bonded silicon-on-glass wafer using ultrasonic agitation to obtain uniform silicon film and good surface finish in deeply dissolved silicon-on-glass (DDSOG) process has been studied in KOH solution. Etch-back characteristics of ptype (100) 4inch SOG wafer have been explored under the different ultrasonic power. It has been observed that the characteristics of etch-back such as the etch rate, etch uniformity and surface roughness were evidently improved under 120W ultrasonic power agitation. The etching uniformity was less than +/-1% on the whole wafer. And the root-mean-square roughness (R(rms)) of 20.6nm was achieved after 360 mu m thickness silicon being etched. Some shortcomings of ultrasonic agitation such as damaging membrane and reducing the bonding intensity are observed and how to overcome these disadvantages in DDSOG process is also discussed. Using this technology, a tunneling gyroscope with an out-of-plane, 30 mu m thickness beam was successfully fabricated

Investigations on ElectroHydroDynamical Drop-On-Demand Inkjet Printing

The effects of electrohydrodynamical(EHD) drop-on-demand inkjet variables on the droplet diameter are presented in this paper. The EHD printer uses a high pulsed voltage to generate strong electric field in the vicinity of the apex of the dome-shaped liquid meniscus and thus micro-jetting ejection of droplet comes forth. And the liquid shaping processes are revealed through CCD. The droplets with 50 mu m diameter were formed on the silicon collector. We have evaluated systematically the effects of EHD inkjet printing design variables such as the voltage, the frequency, the solution concentration, the voltage duty cycle and the contact angle on the droplet diameters. The experiment results show the droplet diameters get larger with the voltage, the solution concentration and the voltage duty cycle increasing respectively. And when the frequency, the contact angle increases respectively, the droplet diameters get smaller