Nanochannel Fabrication

Nanofluidic Altering is based on an electrokinetic trapping mechanism enabled by recent advances in nanochannel fabrication. A nanofluidic filter consists of two microfluidic channels bridged by buffer-filled nanochannels which act hke an ion-selective membrane. The technique is a relatively new technique which has a demonstrated potential for sample enrichment. A schematic chip layout of a nanofluidic Alter is given in Figure 50.36. 

With the rapid development of micro- and nanochannel fabrication technologies and the increasing need for simple, portable, yet sensitive particle counting and sizing device, there is a resurgence in the field of RPS, and many researchers tried RPS particle detection in a microfluidic or nanofluidic chip. 

Many techniques have been developed to fabricate nanochannels or nanocharmel arrays. Several general approaches of nanochannel fabrication relevant to nanofluidics are summarized in the following sections. 

Nanochannel Fabrication with Solid-State Fabrication Techniques... 

Top-down nanochannel fabrication techniques are developed mainly over the last decade with state-of-the-art micromachining facilities. Various kinds of nanochannels, such as short nanopores, 2D nanoslits, and ID nanotubes, have been fabricated and tested for different applications. Small nanopores are made based on the reflow of surface atoms under the irradiation of focused ion or electron beams. 2D nanoslits can be easily batch fabricated with either etching of enclosed sacrificial lines or bonding of two chips with one having etched nanometer deep open channels on it. ID nanochannels need advanced lithography capability, and many techniques are not suitable for batch fabrication. Some more details of making these three types of nanochannels are as follows. 

Fabrication of 2D Nanochannels Fabrication of 2D nanochannels can be easily done with state-of-the-art microfabrication facilities based on either sacrificial lines or bonding of a flat chip with a chip with etched grooves of nanometer depth. These nanochannels can be batch-fabricated and easily integrated with other components to make integrated nanofluidic devices. While other techniques may be available to make 2D nanochannels, we will only briefly introduce the two most common techniques, namely, those based on sacrificial lines and bonding because they can be readily made with easily accessible microfabrication facilities. 

Nanochannel fabrication with microfabrication techniques takes advantage of the rapid development of semiconductor industry and provides the opportunities of fabricating nanochannels of various configurations. In addition, it is relatively... 

Lee C, Yang EH, Myung NV, George T (2003) A nanochannel fabrication technique without nanolithograph. Nano Lett 3 1339-1340... 

To prepare membranes with artificial nanochannels, one can start with several polymer materials such as polyimide (PI), polycarbonate (PC), and polyethylene terephthalate (PET). A prerequisite to apply these kinds of polymers for nanochannel fabrication is that they are easy to process and susceptible to different etching techniques to produce nano-sized channels of different morphologies. Current methods for this purpose include ion-track-etching, electrochemical etching, and laser techniques. Once the nanochannels have been produced, one needs to functionalize the channel inner wall to obtain different functions. Following are some examples of polymer decorated nanochannels. 

Nanofluidic systems constracted for fluorescent single molecule detection are relatively simple with nanochannels connected to microchannels at each side of the nanochannels and molecules of interest are usually introduced into the nanochannels through electrophoresis for fluorescent detection. Various kinds of nanochannel fabrication techniques such as focused ion beam milling and nanoimprint Uthography have been used to fabricate the nanofluidic channels. The fabricated nanofluidic system is usually positioned on a fluorescent microscope for fluorescent single molecule detection. 

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