MANUFACTURING
Soft Lithography Explained
Soft lithography is the casting technique that put microfluidics within reach of any lab. By moulding a soft polymer (PDMS) against a patterned master, researchers can make a sealed microfluidic chip in a day. Here is how it works.
What is soft lithography?
Soft lithography is a family of techniques that replicate micro-scale patterns by moulding a soft elastomer — almost always PDMS — against a rigid master. The most common form, replica moulding, is how the majority of research microfluidic chips are made.
The process, step by step
- Make a master — a patterned mould of the channel network, traditionally photoresist (e.g. SU-8) on a silicon wafer made by photolithography, or a CNC-machined metal mould.
- Mix and pour PDMS — combine base and curing agent, degas to remove bubbles, and pour over the master.
- Cure — bake until the PDMS sets into a solid, flexible slab.
- Peel and finish — release the PDMS, cut to size, and punch inlet and outlet ports.
- Bond — plasma-treat and seal the PDMS to glass or another PDMS layer to close the channels.
Why it transformed microfluidics
- Cheap and fast — no cleanroom needed once the master exists.
- One master makes many chips, enabling quick design iteration.
- Captures sub-micron features with high fidelity.
Limitations and scaling
Soft lithography is a prototyping method, not a production one — casting by hand does not scale to millions of identical parts, and PDMS has material drawbacks. For volume, the same design is transferred to thermoplastics via injection moulding. A practical route is to machine a durable master: we make reusable aluminium moulds for PDMS casting, and explain the full journey in prototype to scale.
Frequently asked questions
What is soft lithography?
A technique for making microfluidic devices by moulding a soft elastomer (PDMS) against a patterned master, then bonding it to a substrate to seal the channels.
What is the difference between soft lithography and photolithography?
Photolithography patterns a rigid master using light and photoresist; soft lithography then replicates that pattern by casting soft PDMS against the master.
Why use PDMS for soft lithography?
It is inexpensive, optically clear, flexible, faithfully replicates fine features, and bonds easily to glass by plasma treatment.
Can soft lithography be used for mass production?
No — it is a prototyping and low-volume method. High volumes use injection moulding of thermoplastics.
From master to production
Prototyping in PDMS?
We machine durable aluminium moulds for casting and take proven designs through to moulded production. Upload a design for a quote.
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