Micro-reactors for characterization of nanostructure-based sensors

Abstract

Fabrication and testing of micro-reactors for the characterization of nanosensors is presented in this work. The reactors have a small volume (100 μl) and are equipped with gas input/output channels. They were machined from a single piece of kovar in order to avoid leaks in the system due to additional welding. The contact pins were electrically insulated from the body of the reactor using a borosilicate sealing glass and the reactor was hermetically sealed using a lid and an elastomeric o-ring. One of the advantages of the reactor lies in its simple assembly and ease of use with any vacuum/gas system, allowing the connection of more than one device. Moreover, the lid can be modified in order to fit a window for in situ optical characterization. In order to prove its versatility, carbon nanotube-based sensors were tested using this micro-reactor. The devices were fabricated by depositing carbon nanotubes over 1 μm thick gold electrodes patterned onto Si/SiO(2) substrates. The sensors were tested using oxygen and nitrogen atmospheres, in the pressure range between 10(-5) and 10(-1) mbar. The small chamber volume allowed the measurement of fast sensor characteristic times, with the sensors showing good sensitivity towards gas and pressure as well as high reproducibility.

A Review of Implementing ADC in RFID Sensor

“…A previous microreactor containing one CNT microsensor inside has already been fabricated following the same directions explained, but without any embedded electronics, being all measurements made from outside [22,59].…”

“…The CNT gas microsensors designed for this system are planned to present a gas free resistance between 80 kΩ and 100 kΩ. Previous experiments indicate a resistance variation between −0.001% and +20% under gas exposure [59]. If a 4 A biasing current is applied to the sensor, the minimum resistance variation will correspond to a 2.347 V variation on the sensor signal.…”

Local Laser Annealing of Contacts Between MWCNTs and Metallic Electrodes

“…A frequently used approach to connect nanotubes to patterned metal electrodes is based on a controlled deposition by ac dielectrophoresis (DEP) process from liquid dispersions [5][6][7]. However, the electrical and thermal contacts formed between CNTs deposited by DEP and metallic films are usually poor [7][8][9] and further processing is required in order to improve these contacts. For this, conventional (global) thermal treatment or localized annealing is usually employed [10][11][12].…”

Study of the control process and fabrication of microstructures using a tip-based force control system

“…The comparatively recent development of micro-and nanomachining technologies has become a popular research topic and is attracting increasing research attention worldwide. [1][2][3][4][5] Various microstructures, including microgrooves, microchannels and even threedimensional (3D) microstructures, which play important roles in the microchip cooling field, 6 chemical material transport, 7,8 solar cell, 9,10 photovoltaic manufacturing 11,12 and surface-enhanced Raman scattering (SERS), [13][14][15] have been machined successfully by the existing micro/nanomachining methods including photolithography, focused ion beam (FIB), laser-based processes, micro-electrical discharge machining (EDM) and microcutting. Photolithography 16,17 and FIB 18,19 process methods could fabricate nanostructures with high precision.…”