1. NW-FET Fabrication
MEMS (Micro-Electro-Mechanical Systems) Fabrication
(a) A mask pattern design; (b) Inner-electrode mask pattern;
(c-e) Optical and SEM photos of the expanded FET devices;
(f) A nanowire of 40nm in diameter located between source and drain electrodes of 2 um separation.
(a) A chip with NT/NW-FET devices on a circuit board; (b) A PDMS microfluidic channel;
(c-d) Experimental setting containing NT/NW-FET coupled with a PDMS microfluidic channel;
(e) Measuring the current of NT/NW-FET by a detection system of preamplifier and lock-in amplifier.
Schematic illustration for an NT/NW-FET experiment.
2. NW/NT-FET Detection
The CgA released from neurons can be detected by CgA-Ab/SWCNT-FETs. a) When neurons are stimulated by glutamate, the voltage-gated Ca2 + channels at the axon terminal will be opened and allow the entrance of Ca2 + into the cytosol. The Ca2 + will induce the fusion of synaptic vesicles with the plasma membrane to release CgA, which will then bind to the CgA-Ab immobilized on the SWCNT-FET. b) Before the neuron experiment, a negative control without neurons on the FET device was performed by adding glutamate (50 mm) to the CgA-Ab/SWCNT-FET. No change in Isd could be detected. c) In situ detection of the Isd changes elicited by glutamate. The coverslip was positioned on the FET device with neurons facing the circuit, as illustrated by the inset cartoon and indicated by “cell” in the current trace. Glutamate (50 mm) was then added to stimulate the neurons to release CgA. The Isd was measured in the ambient solution at V= 10 mV with a modulation frequency of 377.7 Hz throughout the experiment. (Small, 3, 1350-1355 (2007))
In situ detection of the CgA released from a living chromaffin cell by CgA/SWCNT-FET. (a) A schematic illustration of using CgA/SWCNT-FET to monitor the CgAreleased froma single chromaffin cell in the histamine-evoked exocytosis. (b) Real image of a single chromaffin cell manipulated by a glass micropipette onto aCgA/SWCNT FETdevice. (J. Phys. Chem. B, 112, 9165-9173 (2008))
Environmental electrolytes with different Debye—Hückel screening lengths and the AFM surface topographs of a SiNW- FET. Real-time electrical measurements of the association and dissociation of GST on a GSH/SiNW-FET in (a) 0.1 × PBS (black curve) and 1 × PS (red curve) of D = 2 nm and (b) 0.01× PBS (black curve) and 0.1× PS (red curve) of D = 6.6 nm. The (c) top-view and (d) profile images of an unmodified SiNW-FET scanned by AFM. The wire has width, length, and thickness of 200 nm, 6 m, and 50 nm, respectively. (e) The lumpy AFM image evidences the association of GST with the GSH/SiNW-FET. (f) The effective removal of GST by 10 mM GSH washing is confirmed by the clean surface topograph of the SiNW-FET device. (Nano Today, 4, 235-243 (2009))