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Interlayer bonding structures for manufacturing microfluidic devices Disclosure Number: IPCOM000243005D
Publication Date: 2015-Sep-08
Document File: 3 page(s) / 182K

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Microfluidic devices typically require a top sealing layer to be robust, convenient to handle and for holding macroscopic amounts of liquids or samples. Adhesives used for attaching a sealing layer to a microfluidic device often leak and contaminate critical parts of the microfluidic devices. This problem is solved by creating special geometries called interlayer bonding structures, which prevent uncontrolled spreading of adhesive.

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Interlayer bonding structures for manufacturing microfluidic devices

The method disclosed here relates to the manufacturing of capillary-driven microfluidic chips comprising sample loading structures (SLS) that have a volume capacity of 1 up to tens of microliters. The method addresses a major problem in microfluidic devices, which is the hybrid integration of a thin microfluidic layer with high resolution structures and a low-cost and thicker layer with openings for pipetting a sample. The method uses special geometries, called interlayer bonding structures (IBSs), to confine a liquid adhesive around the SLS. The method minimizes the risk of clogging or contaminating the microfluidic structures while enabling fully-sealed microfluidic chips that are fabricated using high-throughput techniques.

Microfluidic devices are used in numerous analytical and diagnostic tests because they are

portable and enable fast and precise tests. Loading a sample to a microfluidic device, particularly the ones that are based on capillary flow, is however a general issue because pipetted samples are typically several microliters in volume and it is difficult/expensive to create such large volumes in microfluidic devices. Fig. 1 shows a cross-section illustration of sample pipetting to a microfluidic device based on capillary-driven liquid flow. For test reliability, an excess of sample needs to be added to a microfluidic device, where typical volumes range from 1 to 25 microliters. Such volumes would require deep microfluidic structures but such structures are expensive to fabricate and/or have mechanical stability issues (e.g. when these structures need to be sealed). Instead of being deep, such structures can have a large surface area but this still increases the manufacturing cost of microfluidic devices and lowers their portability. In addition, samples should not leak outside the area where they are loaded, in particular if the sample is close to capillary active structures (e.g. wettable microchannels, etc.), and should be well retained to avoid safety issues (e.g. with blood sample contamination) and minimize evaporation.

Figure 1: Typical layout of a microfluidic device made from a base layer with engraved microfluidic structures and a cover layer having an opening for loading a liquid sample . When an adhesive is used for bonding these two layers, the adhesive easily spreads and contaminates into the microfluidic structures.

    Microfluidic devices typically comprise a single or a multi-layer of plastics, polydimethylsiloxane (PDMS), silicon, glass, paper, and printed circuit boards (PCB) and are


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fabricated using various techniques, such as injection molding, hot embossing, soft lithography, etching, photolithography, cutting, drilling and 3D printing. These layers are typically thin (less than 1mm) because thicker substrates may not be available (e.g. Si) or expensive/time-consuming to pattern (e.g. drilling holes in glass). A 2...