Reliable magnetic reversible assembly of complex microfluidic devices: fabrication, characterization, and biological validation |
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Authors: | Marco Rasponi Francesco Piraino Nasser Sadr Matteo Lagan?? Alberto Redaelli Matteo Moretti |
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Affiliation: | (1) Bioengineering Department, Politecnico Di Milano, Piazza Leonardo Da Vinci 32, 20133 Milan, Italy;(2) IRCCS Istituto Ortopedico Galeazzi, Via Galeazzi 4, 20161 Milan, Italy;(3) Gruppo Ospedaliero San Donato Foundation, Corso Di Porta Vigentina 18, 20122 Milan, Italy |
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Abstract: | Current standard procedures for fabrication of microfluidic devices combine polydimethylsiloxane (PDMS) replica molding with
subsequent plasma treatment to obtain an irreversible sealing onto a glass/silicon substrate. However, irreversible sealing
introduces several limitations to applications and internal accessibility of such devices as well as to the choice of materials
for fabrication. In the present work, we describe and characterize a reliable, flexible and cost effective approach to fabricate
devices that reversibly adhere to a substrate by taking advantage of magnetic forces. This is shown by implementing a PDMS/iron
micropowder layer aligned onto a microfluidic layer and coupled with a histology glass slide, in union with either temporary
or continuous use of a permanent magnet. To better represent the complexity of microfluidic devices, a Y-shaped configuration
including lower scale parallel channels on each branch has been employed as reference geometry. To correctly evaluate our
system, current sealing methods have been reproduced on the reference geometry. Sealing experiments (pressure control, flow
control and hydraulic characterization) have been carried out, showing consistent increases in terms of maximum achievable
flow rates and pressures, as compared to devices obtained with other available reversible techniques. Moreover, no differences
were detected between cells cultured on our magnetic devices as compared to cells cultured on permanently sealed devices.
Disassembly of our devices for analyses allowed to stain cells by hematoxylin and eosin and for F-actin, following traditional
histological processes and protocols. In conclusion, we present a method allowing reversible sealing of microfluidic devices
characterized by compatibility with: (i) complex fluidic layer configurations, (ii) micrometer sized channels, and (iii) optical
transparency in the channel regions for flow visualization and inspection. |
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