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Publication Date: 2015-Jun-22
Document File: 13 page(s) / 5M

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Methods for making microfluidic connectors used in analytical devices

I.          Background

Microfluidic connectors are commonly required for making gas-tight fluidic connections with microfluidic flow channels such as provided by capillary-scale tubing, for example tubing with inside diameters on the scale of a few millimeters or fractions of a millimeter (e.g., micrometers).  Prior solutions include attaching fittings to plates with channels milled or etched into them.  Such microfluidic connectors generally perform well, but their fabrication often involves chemical etching (wet etching) and diffusion bonding (solid-state welding).  Both chemical etching and diffusion bonding are relatively complex, time consuming, and expensive, and the process yield from fabrication utilizing such techniques is limited.  

II.        Solution

To address the problems discussed above, this article proposes two analytical sealing devices and associated methods for making leak-free microfluidic connections that are simplified and utilize raw materials that are widely available.  The components employed in these methods can be fabricated from readily available raw materials capable of being joined together in a leak-free manner by a low-cost welding process (for example, brazing) or other joining process.  One example is stainless steel. 

Figures 1 to 3 illustrate the first method.  Figure 1 is an exploded view of a microfluidic connector assembly showing three analytical sealing devices (1) and a microfluidic tube (2).  Each sealing device (1) is configured to provide a fluidic connection between the tube (2) and a fluidic component (not shown) coupled to the sealing device (1).  In the illustrated example, the sealing device (1) has a relatively large port (3) leading into an internal bore that transitions to a relatively small port (4) that is to be coupled to the tube (2).  The large port (3) can be threaded as shown or otherwise adapted as needed for coupling to a desired fluidic component, one example being a fitting communicating with small diameter tubing of a variety of materials.  A ferrule with or without a compression bolt can be used to connect the tubing to the sealing device or, if the tubing is metal, the tubing can be brazed to the fitting (not shown).  At the end where the small port (4) is located, the sealing device (1) has a self-locking feature (5) described further below.

The tube (2) has a tube wall surrounding a center bore (6).  Generally, the tube (2) can have any dimensions typical for microfluidic applications.  As an example, the tube (2) can have an outside diameter (OD) of 1/16 inch (about 1.6 mm) and an inside diameter (ID) of 0.010 inch (about 0.25 mm).  The center bore (6) extends from one axial end to the other axial end of the tube (2).  The axial tube ends can be configured as desired for coupling to fittings, other tubing, flow or pressure sources, etc., open to the atmosphere, or capped...