Soft and rigid two-level microfluidic networks for patterning surfaces

Abstract

We describe the microfabrication and use of elastomeric and rigid two-level microfluidic networks (µFNs), made of poly(dimethylsiloxane) (PDMS) or Si, for patterning surfaces. The first level corresponds to microchannels and the second to via holes through the µFNs serving as filling and venting ports. µFNs in PDMS are manufactured using a 'sandwich' replication from a microfabricated four inch mold structured with SU-8 photoresist, which is planarized by mechanical polishing. µFNs in Si are microfabricated using deep reactive ion etching. Both types of µFNs can be positioned onto a substrate, creating sealed microchannels, filled with different liquids, flushed, removed and reused. These two-level µFNs allow us to access the ports from the rear, minimize interchannel crosstalk, and are economic of solutions. The channels are made wettable so that the liquids can flow spontaneously into the conduits, but stop at the venting ports. The sealing of the conduits usually requires that either the µFN or the substrate be soft. A strategy for using hard two-level µFNs, in Si, for patterning hard substrates is presented: despite voids in-between the µFN and the substrate, a water-based solution can be guided by hydrophilic microchannels over a hydrophobic surface. Adjusting the wetting properties of the various surfaces is key to preventing undesired spreading of solutions. We illustrate our concepts by micromolding colored photocurable polymers on glass and patterning proteins as lines on a polystyrene surface.

Hydrodynamic Flow Confinement Technology in Microfluidic Perfusion Devices

“…Chips with a surface area of about 3 × 7 mm 2 are diced, interfaced with tubing and placed in a holding clamp for application. Further details on the fabrication strategy are provided in a previous publication of the authors on microfluidic networks [35]. The limiting step for process upscaling is the bonding to the PDMS lid.…”

Hydrodynamically Confined Flow Devices

“…Further details on the fabrication strategy are provided in a previous publication of the authors on two-level microfluidic networks for patterning surfaces 23 . …”

A microfluidic device for array patterning by perpendicular electrokinetic focusing

“…Hydrodynamic focusing has been applied for particle sorting, alignment and counting (Dittrich and Schwille 2003), with multiple focusing as fluidic switches (Lee et al 2001) but also for a confined patterning of metal and polyelectrolyte structures inside microfluidic channels (Kenis et al 1999(Kenis et al , 2000Shchukin et al 2004). Hydrodynamic focusing is an interesting method to pattern ligand arrays onto biosensors as compared with alternative microfluidic techniques such as stamping and spotting (Chiu et al 1999;Bernard et al 2001;Juncker et al 2001). It is possible to guide cell and protein containing streams inside a flow-chamber and to immobilize the ligands in parallel lanes (Regenberg et al 2004).…”