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Microstructures
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Microstructures give unique properties. They can be created on surfaces by replication of structures from a master or in the bulk by multilayer coextrusion. We have several techniques to create microstructures at our disposal. Two examples are shown below to demonstrate our capabilities.

  
Example A: Injection-molded ¼-wave retarder element:

The optical properties of a material can be changed by introducing microstructures with features smaller than the wavelength of light (< λ/n ), based on the form birefringence effect.
< Ref.: R.Wimberger-Friedl, Proc.Ann.Techn.Conf. SPE, New York, 1999, 476 >


High volume application requires low-cost technology --> Replication by injection molding --> Mold insert (stamper) containing microstructure


Options for mold inserts:
A) Lithography (E-beam, DUV) + Anisotropic etching (RIE) in Si or SiO2
B) Lithography in deep resist (E-beam, DUV, SU-8) + Electroplating Ni

  
drawing insert manufacture
Steps in insert manufacture by lithography + RIE
Typical result of injection-molding polycarbonate with SiO2 mold insert:
  
photograph: structures of 250 nm
One can see a replication of structures of 250 nm with an aspect ratio of 4!
Example B: Coextruded multilayer ceramic capacitor

Instead of creating grating structures at the surface by replication there are also ways to create grating structures in the bulk of the material by alternating two materials in a multilayer stack. This can be achieved by a special coextrusion technique with layer multiplication in the channel by a special split-and-join element.

  
drawing multilayer

In this way the number of layers increases exponentially with the number of elements in the channel. It can be extended to more than two types of materials.
An example is a green ceramic multiplayer capacitor with alternating dielectric and conductive layers (3 different materials are coextruded in the sequence ABAC and multiplied). The resulting structure is shown in the cross-section after selective back etching of binder A and binder C.

  
photograph etched edge
Read more:

+ Polymer materials and microstructures

Microstructures

+ Photoreplication