PDMS in Microfluidics: Properties, Pros and Cons

What is PDMS?

PDMS is a silicone elastomer supplied as a two-part kit — a base and a curing agent — that is mixed, poured over a patterned mould and cured into a soft, rubbery, optically clear solid. Channels are formed by casting against a master, then the moulded slab is bonded to glass or another PDMS layer. This process is called soft lithography.

Why PDMS is so popular

• Fast and cheap to prototype — cast and cure a chip in hours, with no industrial tooling.
• Optically clear — transparent into the visible and near-UV, good for microscopy.
• Gas-permeable — lets oxygen and CO₂ reach cells, valuable for cell culture and organ-on-a-chip.
• Flexible — enables integrated valves and pumps via multilayer soft lithography.
• Easy plasma bonding — forms strong, irreversible seals to glass and itself.

The limitations of PDMS

• Absorbs small hydrophobic molecules — can soak up drugs and dyes, skewing assays.
• Not mass-manufacturable — casting does not scale to millions of identical parts.
• Evaporation and deformation — water vapour permeates, and the soft material can sag in fine features.
• Surface recovers hydrophobicity — plasma-treated PDMS gradually reverts, as covered in our surface treatment guide.

When to move beyond PDMS

PDMS is ideal for proving a concept, but products that need scale, tight chemical compatibility or regulatory manufacture usually transition to thermoplastics such as COC, COP or PMMA made by injection moulding. The trick is to plan that transition early — see prototype to scale. PDMS can also be injection moulded for elastomer parts at volume.

Casting PDMS well

Good PDMS chips start with a good mould. We machine reusable aluminium moulds for PDMS drop casting — a durable alternative to fragile silicon masters.

Frequently asked questions