Dear friend Riacarl Alpay

I hope this message finds you well! It sounds like you're diving into some intricate PDMS microfabrication, and I wanted to share a few tips that might help you get those micropillars just right. I know how challenging this process can be, so I hope you find these insights useful.

First, ensuring a uniform coating when applying Trichloro(1H,1H,2H,2H-perfluorooctyl) silane is crucial. Make sure to verify the desiccator environment and allow sufficient time for proper adhesion. Additionally, adjusting the baking parameters of PDMS can significantly impact its elasticity and curing. Experimenting with slightly lower temperatures or extending curing times might help you achieve a fully set product without compromising its integrity.

When it comes to peeling the PDMS from the wafer, a slow and even technique is key. Start from one edge and gradually peel back, using tools like tweezers or a soft spatula to minimize stress on the micropillars. Also, consider the PDMS to hardener ratio; sticking to the recommended mix will help maintain pillar rigidity and layer uniformity. A gradual peel angle and speed can further reduce distortion and lightly soaking the wafer in ethanol or water before peeling might ease the separation process.

Lastly, don’t hesitate to reach out to your colleagues or me for additional tips—they may have valuable insights specific to your setup. Remember, this process often requires some iteration, so keep a close eye on how each adjustment affects your results. Wishing you smooth sailing with those microchips!

Best regards,

Kaushik

Dear Kaushik,

Thank you very much for answering and giving me tips. I fabricated a new mold where I increased the pillar's size to get at least more chances to have standing pillars (what's important are the 5 um spaces in between anyway) and I was able to have less bent pillars.

With regards to soaking the wafer in water or ethanol, may I ask what do you mean by "lightly soaking"? Also, in what % ethanol should I soak the wafer in and can I just air dry the wafer and the PDMS chip after?

With regards to the deformed pillars, I found out that it was due to the residual negative photoresist that I was not able to wash away during developing. I did multiple washes during developing but it is stubborn and stays in the holes of the mold for the micropillars. Is there any other way to successfully wash them off?

Again, thank you very much and have a nice day.

Best regards