What is PDMS mold?

Polymethylsiloxane (PDMS) is material that is optically clear, and generally considered to be inert, non-toxic and non-flammable. This document describes how to mix, degas and cast PDMS onto a mold that has been made by your favorite technique (UV lithography, Ebeam lithography…)

What is SU-8 mold?

These are fabricated SU-8 molds on a silicon wafer. The molds are used to cast PDMS biochips used to study cancer cells. Equipment used: Laurell spinner to spin the SU-8 photoresist. Hotplate to soft-bake the SU-8 photoresist.

How do I remove PDMS from mold?

In order to facilitate the removal of cured PDMS from the silicon mould, the clean wafer was silanised by immersion in a 1% perfluorooctyltrichlorosilane solution in ethanol for 30 min, followed by copious rinsing with ethanol, blow-drying with nitrogen and baking in a 120°C oven for 30 min.

Why is SU-8 used among all photoresists?

SU-8 absorbs light in the UV region, allowing fabrication of relatively thick (hundreds of micrometers) structures with nearly vertical side walls. The fact that a single photon can trigger multiple polymerizations makes the SU-8 a chemically amplified resist which is polymerized by photoacid generation.

What is positive photoresist?

A positive photoresist is a type of photoresist in which the portion of the photoresist that is exposed to light becomes soluble to the photoresist developer. The unexposed portion of the photoresist remains insoluble to the photoresist developer.

How long does PDMS take to cure?

For microfluidic applications, PDMS is typically cured over a master in a plastic Petri dish at 80ºC for 2.5 hours. The curing temperature is limited by the maximum temperature a plastic Petri dish can withstand without warping.

Can you eat PDMS?

Generally, PDMS is vegan as the manufacturing process without the use of animal matter or products derived from animal origin. So it is considered vegan and vegetarians can eat the food with it.

How to remove PDMS from a SU-8 mold?

2.1.1Using wafer tweezers, place the SU-8 mold wafer along with 2-3 drops (use pipette) of the silanizing agent in a Petri dish and put in vacuum desiccator. 2.1.2Attach the desiccator to a vacuum hose on the hood vacuum port. Open the faucet-style vacuum valve. Leave the wafer under vacuum for at least 1 hour.

What kind of alcohol is used in the SU-8 mold?

At this step the design is revealed on the substrate. The SU-8 can be developed thanks to the SU-8 developer. It’s a product from Microchem mainly composed of PGMEA (Propylene glycol monomethyl ether acetate) but you can also develop the SU-8 thanks to Ethyl-lactate or Di-acetone alcohol.

Is the silicon from SU-8 mold hydrophobic?

The silicon from your SU-8 mold is normally quite hydrophilic and thus the PDMS will have a good affinity to it, strong enough to make the peeling impossible and you can only break your mold and go back from the beginning of your process so do not forget this step. It exists several ways to make the silicon hydrophobic.

How to develop a SU-8 mold lithography?

Put your wafer in a crystallizer with 50mL of developer solution. The time of the SU-8 development depends on the thickness of the layer between 1 min to more than 15min. During the development maintain a good agitation to have the best development as possible. Rinse your wafer with isopropanol.