Microfluidic Gasketless Interconnects Sealed by Superhydrophobic Surfaces

Abstract

Existing methods for sealing chip-to-chip (or module-to-motherboard) microfluidic interconnects commonly use additional interconnect components (O-rings, gaskets, and tubing), and manual handling expertise for assembly. Novel gasketless superhydrophobic fluidic interconnects (GSFIs) sealed by transparent superhydrophobic surfaces, forming liquid bridges between the fluidic ports for fluidic passages were demonstrated. Two test platforms were designed, fabricated, and evaluated, a multi-port chip system (ten interconnects) and a modules-on-a-motherboard system (four interconnects). System assembly in less than 3 sec was done by embedded magnets and pinin-V-groove structures. Flow tests with deionized (DI) water, ethanol/water mixture, and plasma confirmed no leakage through the gasketless interconnects up to a maximum flow rate of 100 μL/min for the multi-port chip system. The modules-on-a-motherboard system showed no leakage of water at a flow rate of 20 μL/min and a pressure drop of 3.71 psi. Characterization of the leakage pressure as a function of the surface tension of the sample liquid in the multi-port chip system revealed that lower surface tension of the liquid led to lower static water contact angles on the superhydrophobic-coated substrate and lower leakage pressures. The high-density, rapidly assembled, gasketless interconnect technology will open up new avenues for chip-to-chip fluid transport in complex microfluidic modular systems.

Leakage pressures for gasketless superhydrophobic fluid interconnects for modular lab-on-a-chip systems

“…This is driven by the proximity of the superhydrophobic surface to the edge, which is a function of the method of creating the superhydrophobic surface and should be considered in the development of any alternative fabrication processes. Similar results for liquid bridge attachment at the perimeter of a through-hole have been reported with a different transparent superhydrophobic coating by Zhao et al who hypothesized that the liquid bridge attachment to the perimeter of the through-hole was also affected by the hydrophilic properties of the polymer in the through-hole 46,61 .…”

“…The ball bearings were selected for the alignment structures to enable a broad range of assembly gaps with a small number of mold inserts. In practice, both the v-grooves and alignment structures will be injection-molded 29 or hot-embossed in the polymer directly 46,50,54 .…”

“…1b, i), the fluid path is determined by the attachment point for the liquid bridge which is a function of the hydrophobicity of the polymer and the superhydrophobic film. The coating can be spin-coated up to the edge of the through-hole 46 . For a conventional assembly of a module and a motherboard or two fluidic chips with misalignment between a pair of through-holes the dead volume is much larger, matching the size of the misalignment (Fig.…”

Flexible-templated imprinting for fluorine-free, omniphobic plastics with re-entrant structures

“…The liquid repellency of our bare re-entrant micro-pillars and the vertical micro-cylinder structure were compared. The micro-cylinders were imprinted as described in the previous studies [32]. According to Young's equation [33], a liquid droplet exhibits an equilibrium contact angle θ Y when sit on a smooth, solid surface.…”