Laser Cutting Channel Mold

From LPDwiki

About this protocol: This method avoids photolithography in favor of a simpler technique using adhesive silver film. Many microfluidic platforms require feature sizes that may be too small to fabricate using this method.

Necessary Materials

1. Several petri dishes

  • Petri dishes may be bought from Vet Med Central Services in Haring Hall
  • Generally, 100 mm diameter petri dishes are suitable
  • It is recommended that more petri dishes are prepared than needed, as at least one should be used for testing the laser.

2. Silhouette Printable Silver Foil, 8.5” x 11” sheets, cut into squares that the selected petri dish will accommodate

  • Can be purchased through various sources

3. AutoCAD design, saved in .dxf 2004 format and stored on USB flash drive.

Procedure

Important: Users should be trained on the DPSS laser before use. The specs of the laser can be found at [1]

1. Carefully peel adhesive off of silver foil and apply foil evenly to petri dish surface.

Inside cleanroom

2. Sign into Badger, enable the laser, and ensure that the machine is on, indicated by the “ready” light flashing. The laser can be turned on with the “On” button.

3. Open the WinLase program and draw a circle. Open the dimension menu by right clicking on the object, and change the diameter to 10 mm and the center to (0, 0).

4. Open the properties menu and change the parameters to: mark multiple 30 passes, frequency 30 kHz, speed 200 m/s.

5. With only a silicon wafer on the platform (this should already be taped to the platform), run the program and observe whether the beam can be seen on the surface of the wafer.

Caution: Staring at UV light can potentially cause damage to the eyes. While it is technically safe to look briefly at the beam from behind the shield as this is a class 1 hazard, users should not look at the beam any longer than necessary.

6. If the light was very faint or not present, adjust the platform height. Continue repeating these steps until a bright spot can be seen cutting the wafer surface. The circle object can be deleted once the platform height is satisfactory.

7. Plug the flash drive in and import the .dxf file in WinLase, making sure to use appropriate units (likely 1 unit = 1 mm) and a closing tolerance of 1.

8. There should be a trace of a circle present on the wafer. This marks the center of the cutting area. Place one silver-covered petri dish over the center of the cutting area.

9. Set the parameters for the drawing: 75 passes, 30 kHz, and 200 m/s. Run the laser again. ‘’Note that the platform may need to be lowered by about 0.5 units (two laps) in order to cut the film and avoid cutting into the petri dish.’’

10. Peel the silver film using tweezers to lift one corner. Be careful not to remove the channel area. The topmost silver layer can be peeled off in addition.

11. After all petri dishes have been cut and peeled, the laser can be disabled and the user can sign out and leave the cleanroom.