Spiral Microchannels with Trapezoidal Cross Section Fabricated by Femtosecond Laser Ablation in Glass for the Inertial Separation of Microparticles.

Ala’Aldeen Al-Halhouli,Baider Alhamarneh,Wisam Al-Faqheri,Andreas Dietzel,Lars Hecht

doi:10.3390/mi9040171

Ala’Aldeen Al-Halhouli, Baider Alhamarneh + Show 3 more

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https://doi.org/10.3390/mi9040171

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The fabrication and testing of spiral microchannels with a trapezoidal cross section for the passive separation of microparticles is reported in this article. In contrast to previously reported fabrication methods, the fabrication of trapezoidal spiral channels in glass substrates using a femtosecond laser is reported for the first time in this paper. Femtosecond laser ablation has been proposed as an accurate and fast prototyping method with the ability to create 3D features such as slanted-base channels. Moreover, the fabrication in borosilicate glass substrates can provide high optical transparency, thermal resistance, dimensional stability, and chemical inertness. Post-processing steps of the laser engraved glass substrate are also detailed in this paper including hydrogen fluoride (HF) dipping, chemical cleaning, surface activation, and thermal bonding. Optical 3D images of the fabricated chips confirmed a good fabrication accuracy and acceptable surface roughness. To evaluate the particle separation function of the microfluidic chip, 5 μm, 10 μm, and 15 μm particles were focused and recovered from the two outlets of the spiral channel. In conclusion, the new chemically inert separation chip can be utilized in biological or chemical processes where different sizes of cells or particles must be separated, i.e., red blood cells, circulating tumor cells, and technical particle suspensions.

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In various biomedical, biotechnological, and pharmaceutical applications, the separation and recovery of specific particles from the background mixture is an indispensable step that usually comes directly before multi post-processing stages
For realizing perpendicular walls and overcoming the limitation provided of the conical-shape of the laser beam, a contouring process was directly performed after engraving the microfluidic channel
This confirmed our expectation that the FD force would be dominant for the 5 μm particles and force them to focus at the core of the Dean vortices near the outer wall of the channel

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Introduction

Biotechnological, and pharmaceutical applications, the separation and recovery of specific particles from the background mixture is an indispensable step that usually comes directly before multi post-processing stages. Several microfluidic-based mechanisms have already been developed and tested for the separation of particles and/or cells based on their unique characteristics (e.g., geometry, physical, chemical, or genetic properties). Such mechanisms are mostly classified according to operation principle, under active or passive methods [1]. Active methods including dielectrophoresis (DEP) and separation with magnetic fields are methods that utilize external force to separate between the different particles. A number of review articles have highlighted the available mechanisms of particle/cell isolation using different types of microfluidic platforms [2,3,4,5,6,7]

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