Weigh a sterile 15 mL conical vial and write the weight on the vial
In the laminar flow hood, add the amount of PEG-DA you want to use to the 15 mL conical vial.
Weigh the conical vial again, noting the difference as the PEG-DA weight.
Divide the polymer weight by 0.X to get the total solution weight that you will make.
Subtract the polymer weight from the total solution weight to get the amount of water/initiator that you will add
Calculate amount of initiator solution that you need to add based off of the stock initiator solution concentration and the final initiator concentration that you want (a MiVi = MfVf type equation works fine here, substituting initial and final masses for volumes)
Subtract the amount of initiator solution from the amount of water/initiator required that was calculated in step 5 to get the amount of deionized water that you will add.
Add this amount of water to the PEG-DA in the conical vial, dissolve by vortexing, filter sterilize
If you are encapsulating cells, add the PEG-DA solution to a cell pellet that will give the desired cell concentration, suspend the cells by repeated pipetting.
Add the required amount of initiator solution (filter sterilize if it is not already sterile), mix by repeated pipetting.
Polymerize PEG-DA solution