Patent ID: 11867320
Assignee: NATIONAL RESEARCH COUNCIL OF CANADA
Field: Mechanical elements (Mechanical engineering)
Classification: CPC F  B | IPC B  F

Claim 19:
20. A normally closed polymeric microfluidic valve comprising:
a plastic substrate;
a resilient deformable elastomeric membrane extending across the substrate, the substrate and membrane defining a valve region separating at least two microfluidic channels in a microfluidic device;
a valve seat in the valve region on one of the membrane and the substrate, the valve seat having an adhesion-controlled surface where the membrane and the substrate contact when the valve is closed; and
a control fluid chamber separated and sealed from the microfluidic channels by the membrane,, where:
the adhesion-controlled surface is provided with a relief pattern of microstructures that provide a plurality of separated top meeting surfaces and recessed surfaces, the top meeting surfaces collectively having a cumulative surface area less than 90% of an area spanned by the adhesion-controlled surface, and having fluid-filled voids between the top meeting surfaces when the valve is closed;
the relief pattern is on the valve seat, or a meeting surface of the valve seat; and
the fluid-filled voids reduce adhesion between the membrane and the substrate in the spanned area compared to 1-adhesion if no microstructures were present in the spanned area and compared to 2-adhesion if the membrane and the substrate were in conformal contact over all available surfaces including the top meeting surfaces and the recessed surfaces;
further characterized by at least one of the following listed items:
the cumulative surface area of the top meeting surfaces on the adhesion-controlled surface is between 0.54% and 30% of a total surface area of the adhesion-controlled surface, the total surface area including the cumulative surface area of the top meeting surfaces, a cumulative surface area of the recessed surfaces, and a cumulative surface area of side walls of the microstructures connecting the top meeting and recessed surfaces;
the top meeting and recessed surfaces of the microstructures are separated by a depth d of at least 75 nm, and a mean spacing between adjacent top meeting surfaces is no more than 20 d, and no less than ½ d;
the plurality of distinct top meeting surfaces comprises at least 25 distinct top meeting surfaces, that are not connected by any path restricted to the top meeting surfaces;
the substrate has a stiffness at least one order of magnitude larger than a stiffness of the membrane;
the membrane has a thickness in a range of about 20-1000 pm, and a Young's modulus in a range of about 0.1 to 100 M Pa as measured by ASTM D638;
the membrane is a saturated or unsaturated thermoset rubber, or a thermoplastic elastomer;
the microstructures comprise micropillars formed in a regular array on the adhesion control surface;
the microstructures comprise generally conical or frustoconical micropillars with a cone angle from about 20° to about 130°;
the microstructures comprise micropillars having a nominal diameter of 1 pm to 200 pm;
the microstructures comprise micropillars having rounded tops;
the tops of the microstructures are decorated with nanostructures;
the tops of the microstructures are surface treated to further reduce adhesion between the membrane and the substrate;
the fluid-filled voids have a collective void volume and the microstructures and/or nanostructures have a collective structured volume, wherein the collective void volume is between 50 to 99.5% of a sum of the collective void volume and the collective structure volume when the valve is closed with no pressure differential between the control fluid chamber and the microfluidic channel;
the adhesion-controlled surface is on a valve body separating the channels;
the valve body has a height that extends a full depth of the channels and provides walls that terminate each of the channels, and the valve is a normally closed valve;
the valve body has a height that extends a fraction of a depth of the channels, and the valve is a normally open valve;
the adhesion-controlled surface extends beyond the valve body and covers a top meeting surface of substrate intermediate the channels.