Mar 25, 2009
Nanofluidic channel gets electrical upgrade
Until recently, all nanofluidic channels were electrically passive, but by embedding transverse nanoelectrodes in the device, the number of potential applications can be broadened to include sequencing, flow control via Debye length modulation, and electrochemical spectroscopy.
Numerous methods exist for fabricating passive nanochannels. For example, bulk micromachining, surface micromachining, thermal oxidation with anodic bonding, thermal oxidation with chemical–mechanical polishing, nano-imprint lithography with subsequent dielectric sputtering, and Focused Ion Beam (FIB) milling of solid surfaces. Integrating miniature electrodes presents an additional challenge, but researchers in the US have come up with a solution.
In a recent paper, which was published in Nanotechnology , the authors report a top-down approach involving a combination of conventional photolithography and focused ion beam (FIB) technologies to fabricate a nanofluidic channel (20 nm depth, 50 nm width, and 2 µm length) with embedded transverse nanoelectrodes. The fabricated channels completely reside inside silicon dioxide, which is one of the most widely studied and characterized surfaces across a range of biological applications. Optically transparent borosilicate glass was used to cover the top of the fluidic chip, providing a window for real-time fluorescent microscopy. Parts of the electrodes in contact with liquid were made of platinum for electrochemical compatibility.
The researchers verified the nanochannel fluidic patency through resistivity measurements in phosphate buffered saline (PBS) and electrostatic action on charged fluorescent nanospheres. Platinum nanoelectrode functionality was also tested using transverse resistance measurements in nanochannels filled with air, deionized water and saline solution.
About the author
The work was performed at Purdue University, West Lafayette, IN, USA. Teimour Maleki is a PhD student at the School of Electrical and Computer Engineering (ECE). Drs Mohammadi and Ziaie are both associate professors at the ECE and also affiliated with the Birck Nanotechnology Center.