While there is great interest in 3D printing for microfluidic device fabrication, the challenge has been to achieve feature sizes that are in the truly microfluidic regime (<100 μm). The fundamental problem is that commercial tools and materials, which excel in many other application areas, have not been developed to address the unique needs of microfluidic device fabrication. Consequently, we have created our own stereolithographic 3D printer and materials that are specifically tailored to meet these needs. We review our recent work and show that flow channels as small as 18 µm x 20 µm can be reliably fabricated, as well as compact active elements such as valves and pumps. With these capabilities, we demonstrate highly integrated 3D printed microfluidic devices that measure only a few millimeters on a side, and that integrate separate chip-to-world interfaces through high density interconnects (up to 88 interconnects per square mm) that are directly 3D printed as part of a device chip. These advances open the door to 3D printing as a replacement for expensive cleanroom fabrication processes, with the additional advantage of fast (30 minute), parallel fabrication of many devices in a single print run due to their small size.
Monolithic columns offer advantages as solid-phase extractors because they offer high surface area that can be tailored
to a specific function, fast mass transport, and ease of fabrication. Porous glycidyl methacrylate-ethylene glycol
dimethacrylate monoliths were polymerized in-situ in microfluidic devices, without pre-treatment of the poly(methyl
methacrylate) channel surface. Cyclohexanol, 1-dodecanol and Tween 20 were used to control the pore size of the
monoliths. The epoxy groups on the monolith surface can be utilized to immobilize target-specific probes such as
antibodies, aptamers, or DNA for biomarker detection. Microfluidic devices integrated with solid-phase extractors
should be useful for point-of-care diagnostics in detecting specific biomarkers from complex biological fluids.
DNA has shown great promise as a template for the controlled localization of various materials and the construction of wires with nanometer-dimension cross sections. We have recently developed a strategy for fabrication of nanocapillaries, using DNA-templated nanowires as a sacrificial material. We first form metal nanowires through the selective electrochemical deposition of nickel atop a surface-aligned DNA molecule. We then deposit a thin layer of silicon dioxide on top of the DNA nanostructures. Next, we photolithographically pattern openings over the ends of the wires and etch through the silicon dioxide layer to expose the metal nanowires. Finally, we etch out the DNA-templated nickel nanowires. This process results in the formation of nanocapillaries having the same dimensions as the originally formed DNA-templated nanowires. We have characterized these DNA-templated nanocapillaries using atomic force microscopy, optical microscopy and scanning electron microscopy. These constructs have potential for application in nanofluidics, power generation, sample preconcentration, and chemical sensing.
Capillary electrophoresis arrays have been fabricated on planar glass substrates using photolithographic masking and chemical etching. The photolithographically defined channel patterns were first etched in a glass substrate, and then capillaries were formed by thermally bonding the etched substrate to a second glass slide. High-speed separations of restriction fragment digests were performed on these chips in under 1 minute. Multiple separations in the same channel demonstrated excellent reproducibility. Rapid genetic typing of short tandem repeats on the HUMTHO1 locus have also been performed. Finally, separations with single- base resolution have been successful, indicating that these microfabricated devices will also be useful for high-speed DNA sequencing.
Conference Committee Involvement (12)
Biosensing and Nanomedicine XII
11 August 2019 | San Diego, California, United States
Biosensing and Nanomedicine XI
19 August 2018 | San Diego, California, United States
Biosensing and Nanomedicine X
6 August 2017 | San Diego, California, United States
Biosensing and Nanomedicine IX
28 August 2016 | San Diego, California, United States
Biosensing and Nanomedicine VIII
9 August 2015 | San Diego, California, United States
Biosensing and Nanomedicine VII
17 August 2014 | San Diego, California, United States
Biosensing and Nanomedicine III
25 August 2013 | San Diego, California, United States
Biosensing and Nanomedicine II
12 August 2012 | San Diego, California, United States
Biosensing and Nanomedicine
21 August 2011 | San Diego, California, United States
1 August 2010 | San Diego, California, United States
4 August 2009 | San Diego, California, United States
12 August 2008 | San Diego, California, United States