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Technical References for PDMS Master Molds

3D-printed PDMS Master Molds Specs:

Typical achievable features:

  • Open channels: ~40-50µm in XY (geometry dependent)

  • Channel heights: ~50-200µm commonly used, 10µm minimum Z height

  • Micro-wells and reservoirs: down to ~50µm features

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Resolution is highest for open, accessible features.

 

Printable Geometries:

  • Straight and serpentine channels

  • Cross and T-junctions

  • Droplet generators

  • Gradient Generators

  • Herringbone mixers and Tesla valves

  • Microwells

FAQ

How does the workflow work when ordering PDMS master molds?

Typical workflow:

  1. Customer provides CAD or functional requirements

  2. Design reviewed for printability and mold durability

  3. Design adjustments suggested if required

  4. Master mold printed and post-processed

  5. Mold delivered ready for PDMS casting

Customers may cast PDMS in-house or request support.

 

What are typical turnaround times?

Standard PDMS master molds can be printed in 4-6 hours, thus, next day shipments are possible if requested.
Most projects, however, are ready for shipping within 3-5 business days.

 

How do 3D-printed master molds compare to SU-8 photolithography?

3D-printed master molds:

  • No cleanroom required

  • No photomasks

  • Faster iteration

  • True 3D geometries possible

SU-8 lithography:

  • Higher ultimate planar resolution

  • Higher setup overhead

 

Do the master molds require silanization or release agents?

No. PDMS can be cast directly onto properly post-processed 3D-printed master molds without surface treatment.

 

How durable are 3D-printed PDMS master molds?

With appropriate design and handling, master molds can withstand hundreds of PDMS casting cycles.

Durability depends on:

  • Feature height

  • Wall thickness

  • Demolding forces

  • PDMS curing conditions

 

What surface quality can be expected?

The process delivers a surface finish with an RA value of ~ 0.18µm.

Surface finish is generally not a limiting factor.

 

Can multilayer PDMS devices be fabricated?

Yes. 3D-printed master molds support:

  • Multi-height features

  • Alignment structures

  • Multi-layer PDMS assembly

 

What geometries are not possible with PDMS molding?

PDMS molding cannot reproduce:

  • Fully enclosed channels

  • Strong Undercuts (max. 45° recommended)

  • Re-entrant geometries

Such features require monolithic 3D printing or multi-part molds.

 

Is PDMS still preferable over direct 3D printing in some cases?

Yes. PDMS is preferred when:

  • Gas permeability is required

  • Elastic deformation is needed

  • Surface chemistry modification is critical

  • Established biological protocols depend on PDMS/Silicone

 

When should PDMS master molds NOT be used?

Avoid PDMS casting if the device requires:

  • Fully enclosed internal channels

  • High internal pressure stability

  • Rigid optical path geometry

  • Direct connectors such as Luerlocks

In these cases, 3D printed monolithic microfluidic devices are superior.

 

How should researchers decide between Monolithic 3D prints and PDMS?

Use Monolithic prints if:

  • Geometry is complex or fully enclosed

  • Pressure stability matters

  • Fast iteration without bonding is needed

  • Channel rigidity and solid connectors are necessary

Use PDMS if:

  • Elasticity or gas permeability is required

  • Surface chemistry tuning is critical

  • Chip design needs to be reproduced several times

  • Established PDMS workflows must be maintained

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