FABRICATION

Metal lift-off

1. Photolithography Futurrex photoresist on lithium niobate, using a light-field mask

2. Metal deposition Chromium and gold (Cr/Au) deposited over the whole surface

3. Lift-off Photoresist and excess metal removed, leaving only the IDT pattern

This is the same lift-off idea you've already seen for metal layers in earlier units — deposit everywhere, then remove what you don't want.

PUTTING IT TOGETHER

Bonding the chip

Once the IDT electrodes are patterned onto the lithium niobate substrate, the PDMS microfluidic channel is bonded on top, aligned with the SSAW region between the two IDT sets.

🔩 + 🧪

Two separately fabricated pieces — an electrical device and a fluidic one — become a single working chip.

WORKED EXAMPLE

From design to a working chip

1. Design by rule Set IDT and channel dimensions from known design rules

2. Design by analysis Simulate the wave and confirm frequency and displacement

3. Fabricate Pattern the IDT electrodes with metal lift-off

4. Bond Attach the PDMS microchannel over the SSAW region

5. Test Verify particle focusing and particle separation

Every step exists to control one thing precisely: where the standing wave's pressure nodes fall inside the channel.

UNIT 28 STUDY COMPLETE

💧

Ready for the Fab Challenges?

You've covered Building the Chip.