Engineering 182 Basic Electronic Circuits Lab

LAB DEMOLDING LAB PROCEDURE

The purpose of this lab is to expose the student to a lab-on-a-chip fabrication technique. The student will demold their PDMS LID from the petridish.

The PDMS lids have been curing for several days and must be slowly and carefully removed from the Petri dish. A small spatula will be used to separate the PDMS from the sides of the Petri dish and pry up one edge of the PDMS. The student will very slowly pull the PDMS out of the Petri dish.

DEMOLDING

THOROUGHLY REVIEW THE INSTRUCTIONAL VIDEO ON PRINTING YOUR 1:1 (FULL) SCALE DESIGN, DEMOLDING, AND CLEANING AND ASSEMBLING YOUR CHIP!!!!

THROUGHOUT THE DEMOLDING STEPS THAT FOLLOW, ASSUME THAT TWO SUB- TEAMS OF TWO WITHIN YOUR GROUP WILL PERFORM THESE STEPS; EACH SUB-TEAM WILL DEMOLD ONE OF THEIR TEAM’SLID.

1. Retrieve the Petri dishes containing your lids from the storage location. LATEX OR VINYL GLOVES SHOULD BE WORN ANY TIME THE LID IS TO BE HANDLED. NOTIFY the INSTRUCTIONAL TEAM if a group member has a latex allergy and alternate gloves will be provided. It is VERY IMPORTANT that you not touch or handle the lid with your fingers. Oils and dirt from your hand will interfere with and possibly ruin the chip.

2. During the following steps, you should use a 1:1 (full scale) of the chip design and chip holder to align the pieces of the chipholder-chip assembly. Use the Inventor part file in the classroom drive or DVD to create a 1:1 scale drawing of the chip holder with generic chip. Use this for aligning your detection well with the chip holder.

3. The DEMOLDING PROCESS requires PATIENCE. Choose a team member with a steady hand and patience to perform the chip demolding.

4. First we will demold and cut the lid. To cut the lid, first place the petri dish for the lid over the 1:1 scale printout of the design. Use the precision utility knife to cut out the 2” circular outline of the chip while in the Petri dish (just inside the outer line). Be careful to not move the printout while cutting. Do not remove the lid from the petri dish yet.

5. Place the Petri dish containing the PDMS lid you just cut over the 1:1 scale design printout such that the circular cut is aligned with the 2-inch circle in the printout.

6. Using a fine-tipped permanent marker, mark the necessary access points (where the staging and waste wells are). You only need to punch one hole for the waste well.

7. After pealing the marked lid out with the microspatula, use the punch to make the holes on your marks. Make sure you use the 2mm punch size and keep it perpendicular to the PDMS surface while punching.

Lab 7: PDMS Chip Demolding and Microfluidics Lab Procedure and Worksheets, revised by ysa - 03/06/07 Revised by bct – 09/05/06, 02/17/06 8. Discard the left overs of PDMS and their petri dishes.

Figure 1. PDMS chip, PDMS lid, and chip holder aligned and assembled over design printout.

9. Follow the cleaning instructions in Supplement 2 (located after the Lab 2 procedure) before proceeding to the next step.

10. Verify that the chip and chipholder are clean using the 5x magnifier and light box.

THE REMAINING STEPS REQUIRE PATIENCE AND DILIGENCE AND ARE CRITICAL AS THEY INVOLVE THE ALIGNMENT OF ALL THE CHIP ASSEMBLY PARTS AND ACCESS POINTS!!!

11. Place a chip holder base on the printout created earlier of the generic chip, 12. Place a drop of water in the center of the chip holder base, then transfer the acrylic bottom of the chip to the chip holder base, design-side up and lined up with the design on the print out. The drop if water is to ensure that there is no air between the bottom of the chip and the chip holder. Be sure there are no air bubbles between the chip holder base and acrylic chip bottom. Be sure that the holes line up with both the wells and the chip holder holes drawn on the outline.

PRECISE ALIGNMENT OF THE DETECTION WELL AND STAGING WELLS IS IMPERATIVE!

13. Now do the same with your PDMS LID, once again being sure to keep everything aligned, especially the staging wells and access holes on both the PDMS pieces and the printout. When placing the PDMS lid on the acrylic chip base, make sure you roll the lid onto the acrylic surface to avoid air bubbles.

14. Place the plexiglass chip holder top over the entire assembly, once again while being wary of bubbles, alignment, and possible debris.

Lab 7: PDMS Chip Demolding and Microfluidics Lab Procedure and Worksheets, revised by ysa - 03/06/07 Revised by bct – 09/05/06, 02/17/06 15. Turn the 3 nuts only as much as necessary to hold the top in place and maintain a seal. Be careful not to apply torque beyond the free spinning point, or your chip may not perform properly. This means spinning the loose nuts until they stop, then adding only a slight additional turn, just enough to hold them and the assembly in place and applying only minimal pressure or ALMOST NO PRESSURE to the chipholder and chip. You do not want to compress the PDMS chip at all.

16. When you have finished assembling your chip holder-chip assembly, store it in chipholder case.

FLUIDIC TESTING (time permitting)

17. Repeat the procedures from Lab 2 Segment B to test the fluid flow in your CHIP.

18. If you have PROBLEMS pumping fluid from any well to the detection well, you should try to determine if there are blockages in the channel or other defects from the fabrication process. Once again, the 5x magnifier and light box may be useful here. If you notice any obstructions, contact the instructor for suggestions.

19. Use the SYRINGE to pump dyed water into a staging well, and then to the detection well and waste well.

20. Flush with clear water using the SYRINGE to displace the dyed water from the detection well. NOTE whether the dye can be completely displaced from the detection well .

21. Test fluid flow from each of your staging wells and record the relative success of each. Make a sketch or describe your operational and design issues.

22. As a team RECORD your initial observations about your chip design and operation. NOTE specifically any demolding problems, alignment or other issues with your lid, leaks, general fluid flow, operation of check valves, and ability to flush detection well. These notes will form the basis of discussion in your final report. Place them in your PROJECT NOTEBOOK. It is imperative to make careful observations, take good notes, and prepare for the contents of your report and the final test from this point forward.

23. Check Supplement 1 and try to ascertain the causes of any issues you just encountered.

24. Clean up your table and place all of your team items in your bins and put away the bins. END

Lab 7: PDMS Chip Demolding and Microfluidics Lab Procedure and Worksheets, revised by ysa - 03/06/07 Revised by bct – 09/05/06, 02/17/06 Simple Light Detecti on LAB 7

Item Description Quantity per table Quantity per room Location

1000 ppm concentration of fluorescein for calibration (1 liter) 1 Front

Precision knives 2 Front

Kim Wipes 2 Front

powderless latex gloves 2 Front

Scotch tape several Front

dish soap 1 Sink

1/8" leather punch 1 Table

400 ml glass beaker 2 Table

5 ml syringes 2 Table

Bucket to cover DAD during measurements 1 Table

compressed air 1 Table

Digital Multi-Meter (DMM) 1 Table

Lightboxes 1 Table

power supply with wire leads 1 Table

toolkit 1 Table

Ultrasonic cleaner 1 Table

Petri Dishes (4)

Lab 7: PDMS Chip Demolding and Microfluidics Lab Procedure and Worksheets, revised by ysa - 03/06/07 Revised by bct – 09/05/06, 02/17/06