Abstract
The creation of complex three-dimensional (3D) fluidic systems composed of hollow micro- and nanostructures embedded in transparent substrates has attracted significant attention from both scientific and applied research communities. However, it is by now still a formidable challenge to build 3D micro- and nanofluidic structures with arbitrary configurations using conventional planar lithographic fabrication methods. As a direct and maskless fabrication technique, femtosecond laser micromachining provides a straightforward approach for high-precision, spatially-selective, modification inside transparent materials through nonlinear optical absorption. In this paper, we demonstrate rapid fabrication of high-aspect-ratio micro- and/or nanofluidic structures with various 3D configurations by femtosecond laser direct writing in porous glass substrates. Based on this approach, we demonstrate several functional micro- and nanofluidic devices including a 3D passive microfluidic mixer, a capillary electrophoresis (CE) analysis chip, and an integrated micro-nanofluidic system for single DNA analysis. The possible mechanisms behind the formation of high-aspect-ratio micro- and nanochannels are also discussed. This technology offers new opportunities to develop novel 3D micro-nanofluidic systems for a variety of lab-on-a-chip applications.
Highlights
Microfluidics is a rapidly emerging technology that enables miniaturization and integration for biological, chemical, and medical applications
By use of femtosecond laser direct writing in porous glass immersed in water followed by post-annealing, we demonstrated microfluidic channels with nearly unlimited lengths and arbitrary 3D
In combination with 3D microfluidics we have demonstrated in the previous sections, we are capable of producing integrated micro-nanofluidic systems of complex 3D geometries and configurations in glass in a single continuous step
Summary
Microfluidics is a rapidly emerging technology that enables miniaturization and integration for biological, chemical, and medical applications. The first strategy employs femtosecond laser modification inside glass materials followed by chemical wet etching [29,30,31] With this technique the length of the microfluidic channel that can be fabricated is usually limited to a few millimeters, due to the limited etch ratio between the areas with and without the femtosecond irradiation. By controlling the laser peak intensity and polarization, a single nanocrack with sub-50-nm feature size could be achieved inside porous glass [37] Based on these strategies, several functional devices and their applications are demonstrated, including large-volume hollow chamber [38], 3D passive microfluidic mixer [39], capillary electrophoresis (CE) analysis chip [40], and an integrated micro-nanofluidic system for single DNA analysis [41]. Future opportunities and current challenges for this novel approach are highlighted
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