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Micro- & Nanofluidics (Publications)

Multiplexed In Vitro Selection Of Aptamers Using Nanoporous Sol-Gel Arrays With Integrated Microheaters

Significant progress was made in developing small-scale prototypes of a microfluidic platform that functions very well relative to the conventional filter binding SELEX. Our current methodology utilizes nanoporous silica-based sol-gel droplets to confine different target proteins in microfluidic chambers that are arrayed at specific positions along a micro-channel. Sol-gel is not only suitable for immobilization of large amounts of proteins in a 3-dimensional environment, but also allows protein-nucleic acid interactions. In this study, we created a SELEX-on-a-chip device harboring an array of sol-gel droplets with separate microheaters built underneath each droplet for multiplex binding and partitioning steps of the SELEX procedure. Sol-gel droplets allow the competitive binding of nucleic acid aptamers to different target proteins in each droplet, while the microheaters provides local heating to disrupt aptamer-protein interaction and allow selective elution of aptamers from each droplet.




A Bilayer Resist Method for Creating Silica Microfluidics

In support of a growing collection of lab-on-a-chip applications utilizing inexpensively formed microfluidics, we have demonstrated a new method for creating silica microfluidic networks. Unlike some existing bilayer resist processes involving Hydrogen silsesquioxane (HSQ), this process utilizes a single photolithographic step. The resulting silica microfluidics offer several advantageous material properties over polydimethylsiloxane (PDMS).

Non-planar nanofluidic devices for single molecule analysis fabricated using nanoglassblowing

“Nanoglassblowing” was developed as a method to fabricate integrated micro- and nanofluidic fused silica devices with wide, shallow nanochannels and areas of gradual channel depth change. Using this method, channels were constructed with out-of-plane curvature of channel covers from over ten micrometers to a few nanometers, nanochannel aspect ratios smaller than 2x10-5:1 (depth:width), and nanochannels as shallow as 7 nm. These low aspect ratios and shallow channel depths are difficult to obtain using other fabrication techniques without collapsing the channel cover. The gradual changes also facilitate loading of double-stranded deoxyribonucleic acid (DNA) molecules. The nanochannel depths and aspect ratios formed by nanoglassblowing allowed measurements of the radius of gyration, , of single l DNA molecules confined to slit-like nanochannels with depths ranging from 11 nm to 507 nm.

Integration of Microfluidics to Electrospray Ionization Mass Spectrometry Using a Chip-Embedded SU-8 Eectrospray Tip

We present two methods for creating polymeric microfluidic devices integrated with electrospray tips for use with mass spectrometry. SU-8 was used to create microfluidic channels and electrospray tips. The planar electrospray tips were located at the end of microfluidic channels and were formed using standard photolithography. The encapsulation of the microfluidic channels was accomplished by using thermal and press bonding between two SU-8 layers, or by employing a sacrificial layer removal technique. We successfully coupled these microfluidic chips to a mass spectrometer. In particular, the microfluidic device fabricated with the sacrificial layer removal method shows satisfactory electrospray stability.