Procedure for manufacturing two hydrogel tubes

1. Remove 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) from fridge and sit on bench at for at least 1 hour (to warm up to RT).

2. Weigh out 0.1 to 0.15 g of ammonium persulfate (APS-fridge) into a vial, and top up with water to make 10-wt% solution (do not tare balance). LABEL vial APS.

3. Weigh out 0.1 to 0.15 g of sodium metabisulfite (SMBS-bench) into a vial, and top up with water to make 10-wt% solution (do not tare balance). LABEL vial SMBS.

4. Prepare glass mold by cutting glass tube of required diameter into required length (typically 10-15 cm), blowing it out with filtered air, and sealing both ends with rubber septa.

a. (Optional) If tube needs to be silane-modified, treat glass in appropriate manner (see surface modification SOP.

5. Dispense appropriate volumes of HEMA, MMA and water into vial and swirl until solution is clear.

6. Lie out two syringes (usually 3 or 5 ml), filter, filter adapter and four 20G needles on the bench. Attach filter and adapter on one syringe, and a needle onto the other syringe.

7. Puncture one septa of each glass mold with a needle and leave them in there in there.

8. Add volume of APS to the monomer solution and swirl until clear.

9. Apply vacuum to the monomer mixture vial and remove dissolved gas from monomer mixture (2 minutes).

10. Add volume of SMBS to the monomer solution and swirl until clear. Polymerization has now started

11. Slowly withdraw monomer mixture into the syringe, taking care not to introduce bubbles.

12. Remove needle and push through filter into second syringe.

13. Remove the filter and adapter, and place fresh needle onto syringe

14. Inject into glass molds, taking care not to leave any bubbles in the glass mold.

15. Place in chuck of stirrer at appropriate speed. Ensure chuck is firm on the glass mold.