Silicon nanowire field-effect chemical sensor

This thesis describes the work that has been done on the project “Design and optimization of silicon nanowire for chemical sensing”, including Si-NW fabrication, electrical/electrochemical modeling, the application as ISFET, and the build-up of Si- NW/LOC system for automatic sample delivery. A novel top-down fabrication technique was presented for single-crystal Si-NW fabrication realized with conventional microfabrication technique. High quality triangular Si-NWs were made with high wafer-scale yield and scalable lateral dimensions down to 10 – 20 nm and lengths up to 100 m. The thick microscale electrical contact regions formed a continuous layer of single crystal silicon, which provide an easy way for ohmic contact formation. The importance of impurity doping concentration control, ohmic contact formation, and interface charge/surface states reduction during fabrication was demonstrated with either electrical measurements or finite-element simulation. In order to understand the behavior of Si-NW device in solution, an electrical/electrochemical model was developed and discussed. Both 2D analytical model and 3D numerical model were developed to describe the conductance behavior of multigate Si-NW devices. The fitting to the experimental data for both models with the same dimensions and doping profiles proved the accuracy of both models. Finally, the 3D numerical model was used for the sensitivity analysis. Since we are working with Si-NW sensor for surface potential change measurements in solution, the most popular method, which is pH measurement, was used to characterize the sensor behavior. Three variations of SiO2 gate oxide and an ALD Al2O3 gate oxide had been deposited on the nanoISFET and titration experiments were used to assess the pH behavior and sensitivity. The data was analyzed with the well-established site-binding model and demonstrated the near ideal Nernstian pH response of the Si-NW nanoISFET with an Al2O3 gate oxide. Finally, an integrated LOC label-free biosensing platform was presented for automatic small volume sample transport and sensing. The entire platform consists of a Si-NW biosensor chip, integrated with a PDMS microfluidic channel, and a chip holder with all electrical read-out, which is ideal for biosensing application

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

Liquid gating elastomeric porous system with dynamically controllable gas/liquid transport

【Abstract】The development of membrane technology is central to fields ranging from resource harvesting to medicine, but the existing designs are unable to handle the complex sorting of multiphase substances required for many systems. Especially, the dynamic multiphase transport and separation under a steady-state applied pressure have great benefits for membrane science, but have not been realized at present. Moreover, the incorporation of precisely dynamic control with avoidance of contamination of membranes remains elusive. We show a versatile strategy for creating elastomeric microporous membrane-based systems that can finely control and dynamically modulate the sorting of a wide range of gasesandliquids underasteady-stateapplied pressure,nearlyeliminate fouling,and can be easily applied over many size scales, pressures, and environments. Experiments and theoretical calculation demonstrate the stability of our system and the tunability of the critical pressure. Dynamic transport of gas and liquid can be achieved through our gating interfacial design and the controllable pores’ deformation without changing the applied pressure. Therefore, we believe that this system will bring new opportunities for many applications, such as gas-involved chemical reactions, fuel cells, multiphase separation, multiphase flow, multiphase microreactors, colloidal particle synthesis, and sizing nano/microparticles.This work was supported by the National Natural Science Foundation of China (grant no. 21673197), the Young Overseas High-level Talents Introduction Plan, the 111 Project (grant no. B16029). 研究工作得到国家自然科学基金委（项目批准号：21673197）和厦门大学校长基金（项目批准号：20720170050）等资助与支持

Bioinspired Universal Flexible Elastomer-Based Microchannels

Flexible and stretchable microscale fluidic devices have a broad range of potential applications, ranging from electronic wearable devices for convenient digital lifestyle to biomedical devices. However, simple ways to achieve stable flexible and stretchable fluidic microchannels with dynamic liquid transport have been challenging because every application for elastomeric microchannels is restricted by their complex fabrication process and limited material selection. Here, a universal strategy for building microfluidic devices that possess exceptionally stable and stretching properties is shown. The devices exhibit superior mechanical deformability, including high strain (967%) and recovery ability, where applications as both strain sensor and pressure‐flow regulating device are demonstrated. Various microchannels are combined with organic, inorganic, and metallic materials as stable composite microfluidics. Furthermore, with surface chemical modification these stretchable microfluidic devices can also obtain antifouling property to suit for a broad range of industrial and biomedical applications.Chemistry and Chemical Biolog

Hot-Pressed Super-Elastic Graphene Aerogel with Bidirectional Thermal Conduction Properties as Thermal Interface Materials

Traditional graphene-based films normally possess high thermal conductivity (TC) only along a single direction, which is not suitable for thermal interface materials (TIMs). Here, a graphene film with excellent bidirectional TC and mechanical properties was prepared by hot-pressing super-elastic graphene aerogel (SEGA). Thermal annealing at 1800 °C improves the further restacking of graphene sheets, bringing high structure stability to SEGA for enduring the hot-pressing process. The junctions and nodes between the graphene layers in the hot-pressed SEGA (HPSEGA) film provide bidirectional heat transport paths. The in-plane TC and through-plane TC of HPSEGA film with a thickness of 101 μm reach 740 Wm−1K−1 and 42.5 Wm−1K−1, respectively. In addition, HPSEGA film with higher thickness still maintains excellent thermal transport properties due to the interconnected structure reducing the effect of the defects. The infrared thermal images visually manifest the excellent thermal-transfer capability and thermal-dissipation efficiency of the HPSEGA films, indicating the great potential as advanced bidirectional TIMs

Barcelona, Lisboa y Forestier: del parque urbano a la ciudad-parque

En 1915 llegó a Barcelona el ingeniero forestal, diseñador de parques y urbanista francés Jean Claude-Nicolas Forestier, llamado para proceder al ajardinamiento de la montaña de Montjuïc, marco de una proyectada Exposición Internacional de Industrias Eléctricas, así como elaborar otros varios proyectos para la ciudad, el más importante de los cuales era el parque de Pedralbes. Doce años después, Forestier fue llamado a Lisboa, con el encargo de elaborar un Plan general de mejoras de la ciudad y, de forma más concreta, de buscar una solución a la prolongación de la Avenida da Liberdade y el rediseño del parque que la coronaba, el parque Eduardo VII. Entre uno y otro momento, el modelo de ciudad de Forestier había madurado y puede considerarse su esbozo de propuesta para Lisboa como la expresión más acabada de su idea de ciudad-parque, idea que influirá en los planteamientos de arquitectos como Le Corbusier

Ion-step method for surface potential sensing of silicon nanowires

This paper presents a stimulus-response method for surface potential sensing of silicon nanowire field-effect transistors (Si-NW FETs). When an ‘ion-step’ from low to high ionic strength is given as stimulus to the surface, a change of current through the Si-NWs is measured. When the surface potential is changed from negative for a bare SiO2 surface to neutral/positive when there is poly-L-lysine adsorption, this change is measured by a change in current variation at the ion-step

Sensitivity and detection limit analysis of silicon nanowire bio(chemical) sensors

This paper presents an analysis of the sensitivity and detection limit of silicon nanowire biosensors using an analytical model in combination with I-V and current noise measurements. The analysis shows that the limit of detection (LOD) and signal to noise ratio (SNR) can be optimized by determining an operating point in the depletion region with a large sensor transconductance, while maintaining a small system output noise amplitude. Both sensor and measurement configurations play equally important roles for optimal sensor performance. The analysis also shows that the LOD and SNR are minimally affected by the sensor cross-sectional geometry and siz

Fabrication of a Cell Fixation Device for Robotic Cell Microinjection

Automation of cell microinjection greatly reduces operational difficulty, but cell fixation remains a challenge. Here, we describe an innovative device that solves the fixation problem without single-cell operation. The microarray cylinder is designed with a polydimethylsiloxane (PDMS) material surface to control the contact force between cells and the material. Data show that when the injection velocity exceeds 1.5 mm/s, microinjection success rate is over 80%. The maximum value of the adhesion force between the PDMS plate and the cell is 0.0138 N, and the need can be met in practical use of the robotic microinjection