TITLE: Open Source Microfluidic Scaffolds
AUTHORS: Harry Felton, Robert Hughes

[STEPS]
?. [Design]
User designs the required microfluid system from the sub-systems available.
?. [Generate Models]
Download, install and open Fusion 360.
NB: Although Fusion 360 works on iOS and Android devices the add-in will not and so a Windows or MacOS device should be used.
?. [Generate Models]
Load the µ-fluid add-in into Fusion 360
?. [Generate Models]
Download the µ-fluid add-in as a zip file from GitHub (https://github.com/dmf-lab/microfluidics)
?. [Generate Models]
Choose module, set parameters and joints. You will have the option to "Export to stl" - this will export the generated model as an stl file (needed for printing) to a folder of the user's choice. The folder selection menu will appear after pressing "Ok".
?. [Generate Models]
Extract zip file to suitable location on your PC/Mac.
?. [Generate Models]
Within Autodesk Fusion 360 go to:"TOOLS -> ADD-INS -> Scripts and Add-Ins... -> Add-Ins" and click on the little "+" icon next to "My Add-Ins". Select the folder "Fusion Add-In" contained within the folder from the previous step.
?. [Generate Models]
Run the µ-fluid add-in. This will be shown in the "TOOLS" and "SOLID" toolbars.
?. [Slice Model(s) For Printing]
Download, install and open Ultimaker Cura. Make sure to follow the correct set-up for your printer.
?. [Generate Models]
Do you need more models? If so,   . If not, continue.
?. [Slice Model(s) For Printing]
Within Ultimaker Cura, open the model(s) generated previously. ("File -> Open File(s)...")
?. [Slice Model(s) For Printing]
Change the profile as appropriate.
NB: This will only work using the downloadable profiles when using Cura for an Ultimaker 3/3 Extended. If you would like to use a different printer, please open the appropriate profile and copy the relevant settings. This should give you a good starting point for printing the scaffolds.
?. [Slice Model(s) For Printing]
The µ-fluid channel profiles can be downloaded from github: (https://github.com/dmf-lab/microfluidics). The profiles are contained within the "Cura Profiles" folder (within the Microfluidics zip).MicroChannels01.curaprofile - Intended for use with 0.1mm nozzle.MicroChannels04.curaprofile - Intended for use with 0.4mm nozzle.
?. [Slice Model(s) For Printing]
Slice models on buildplate within Ultimaker Cura.
?. [Slice Model(s) For Printing]
Save gcode to file and/or send gcode to printer.
?. [Printing]
Print models as you would a normal 3D print with the equipment available to you.
?. [Printing]
Once the print is completed, remove the models from the build plate.
We found the best way to do this was using a stanley knife (or similar) and prising the connectors of the build plate. The channels are very delicate so this takes some practice and patience.
?. [Thermal Bonding to Glass]
Mount the 3D-printed microfluid channel modules onto 1 mm thick glass microscope slides in the desired configuration using the ball-and-socket-connectors.
?. [Thermal Bonding to Glass]
Place a second 1mm thick glass slide on top of the channel configuration to act as a weighting slide
?. [Thermal Bonding to Glass]
Heat the slide-channel-slide assembly at 200\degreeC for 45-60s to bond the PLA thermoplastic to the glass substrate and smooth out inconsistencies.  This is best performed on a temprature controlled hot plate, but heating could also be achieved in an oven or over a flame, however timings and cosistency will vary.
CAUTION: Hot surfaces and heated assemblies can cause severse burns.
NOTE: Heating times will vary depending on the height of the 3D-printed scaffold.
?. [Thermal Bonding to Glass]
After heating, use tweerzers, tongs or oven gloves to transfer the thermally bonded slides onto a metal cooling plate (weighting slide down), and leave for 5 minutes.
?. [PDMS Fabrication]
Use the resulting thermally bonded channel design on the substrate slide as the master mould for PDMS casting. See work by Lake et al. for a more detailed explanation of this step (https://doi.org/10.1038/protex.2015.069).
?. [Thermal Bonding to Glass]
After cooling, slide a blade between the substrate and weighting slides and gently twist to remove the weighting slide.
NOTE: If the channel scaffolds disbond slightly from the subrate during this step, they can be easily rebonded by breifly reheating the substrate slide at 200 deg C without the weighting slide.