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World-to-chip (macro-to-micro) interface continues to be one of the most complicated, ineffective, and unreliable components in the development of emerging lab-on-a-chip systems involving integrated microfluidic operations. A number of irreversible (e.g., adhesive gluing) and reversible techniques (e.g., press fitting) have attempted to provide dedicated fluidic passage from standard tubing to miniature on-chip devices, none of which completely addresses the above concerns. In this paper, we present standardized adhesive-free microfluidic adaptors, referred to as Fit-to-Flow (F2F) Interconnects, to achieve reliable hermetic seal, high-density tube packing, self-aligned plug-in, reworkable connectivity, straightforward scalability and expandability, and applicability to broad lab-on-a-chip platforms; analogous to the modular plug-and-play USB architecture employed in modern electronics. Specifically, two distinct physical packaging mechanisms are applied, with one utilizing induced tensile stress in elastomeric socket to establish reversible seal and the other using negative pressure to provide on demand vacuum shield, both of which can be adapted to a variety of experimental configurations. The non-leaking performance (up to 336 kPa) along with high tube-packing density (of 1 tube/mm2) and accurate self-guided alignment (of 10 μm) have been characterized. In addition, a 3D microfluidic mixer and a 6-level chemical gradient generator paired with the corresponding F2F Interconnects have been devised to illustrate the applicability of the universal fluidic connections to classic lab-on-a-chip operations. [ABSTRACT FROM AUTHOR]

In this paper, we present a simple adhesive-free interconnect technology for microfluidic systems. Reliable connection between microfluidic devices and macroscopic world is a critical issue in many lab-on-a-chip applications. In such interconnections, it is particularly advantageous to avoid liquid adhesives (e.g., epoxy, silicone, etc.) since they can create reliability (blockage or leakage) and reproducibility problems. Our adhesive-free interconnection technology is based on a micromachined silicon flange which is connected to a medical-grade silastic tube using a heat shrink tubing sleeve. The silicon part was fabricated by consecutive anisotropic and isotropic etching processes resulting in a through-hole surrounded by a connection socket ring created using the well known lag effect of deep reactive ion etching. Bio- compatible polyolelin heat shrink tubing (expansion ratio of 2:1 at its shrink temperature of 143 °C) was used to connect and tightly seal the silicon flange to the silastic tube without application of any adhesive. A two-step heat treatment starting from the silicon flange and terminating at the silastic tubing was used to seal the connection. High temperature removability of the heat shrink tubing makes interconnects reworkable. Pull-out force was measured to test the mechanical strength of interconnects with different socket shapes (square, hexagon, octagon, and 32-side circle). Increasing the number of sides improves the mechanical strength with the circular interconnects having an average pull-out force of more than 3N. Leakage tests were also performed to characterize the seal quality. The circular connectors of two different flange sizes showed zero leakage up to the maximum test pressure of 200 kPa (29 psi). [ABSTRACT FROM AUTHOR]