Design Considerations
Gas Permeability	While some plastic and adhesive materials such as polymethylpentene are gas permeable, most materials are not and may require venting ports
Inputs/Outputs	Connecting tubing to plastic microfluidics can prove challenging; consider a 3D printed connector, using ring magnets as gravity fed wells, or a PDMS block on top
Channel Volume	Designing microfluidic channels based on volume enables simpler protocols
Fiducial Marks	The addition of fiducial or registration marks play a vital role downstream in alignment for device assembly, imaging, and automation. Consideration should be made as to locations, accessibility, and orientation of fiducial markings at an early stage.
Fluidic Considerations	Consider the path of fluids through your device, for example sharp corners and rapid expansions can often hinder fluidic movement and lead to bubbles; also, gas permeable devices may lose fluid due to evaporation
Cut Considerations
CAD Software Selection	Most CAD software can produce acceptable file formats for cutters (*.dxf, *.dwg), oftentimes cutters are directly compatible to select CAD software
Cutting Lines	Ensure that no lines are repeated in the drawing to prevent redundant cuts
Cutting Resolution	Best resolution can be achieved by keeping the material as flat as possible when cutting; use painter’s tape on edges of thin substrates to prevent blowing away on laser cutters or an adhesive backing to prevent unwanted skewing and bowing on plotter cutters
Cutting Force	Trial-and-error of laser power/speed and plotter knife force/speed/cut-style is important to get the best cut; an ideal cut for double-sided adhesive would only cut through the first liner and adhesive layer while keeping the bottom liner intact (which will prevent feature ‘droop’ during the assembly process)
Design vs. Cutting	While a design may look perfect on CAD, the order of cuts may cause a feature to blow away or skew during cutting; consider redundant or incomplete cuts that can be manually completed afterwards to overcome these issues
Assemble Considerations
Cleanliness	Dust removal is important for microfluidics, a simple cleaning protocol is using a mild detergent and a sonic toothbrush to directly clean plastic surfaces, followed by a wash and dry with pressurized gas or a microfiber cloth; be wary of harsh organics, which may damage substrates
Feature Removal	Use tweezers to remove all unwanted features cut out from adhesive before assembly; it is best to only remove the top liner and adhesive to prevent feature ‘droop’ during assembly
Peeling Off First Liner	Peeling off the top liner from cut adhesive is best done in one continuous motion if possible; tweezers are useful in complicated areas
Alignment	Using a simple alignment rig (such as a dowel for disc devices) is recommended for aligning adhesive on substrates
Lamination	A laminator or even a smooth laminating roller (McMaster-Carr #7533A12) to apply heavy pressure is important to activate most adhesives to set devices together
Adhesive-Paper Integration	When a paper substrate is integrated into a thin-film adhesive layer, apply additional lamination pressure at the boundary between adhesive and paper to best seal the device