15 Polymer Patterning Flashcards
Photoligraphic
patterning
performed using a positive
photoresist or a negative photoresist.
Introduction of dopants
Dopants can be introduced into the substrate
after patterning
Properties of photoresists
- Ease of conversion between soluble and
insoluble modification or vice versa. - Partially transparent to UV-light.
- Must “resist” treatment during processing.
Negative photoresists.
Backbone or pendant
groups can undergo photoinduced crosslinking
(epoxy, vinyl, or aryl halides). Insoluble in
developing solutions upon crosslinkin
Positive photoresists
Soluble upon exposure to
UV-light.
EBL
E-beam lithography
An electron beam in an SEM is used to pattern a
substrate (negative or positive).
EBL does NOT
require a mask and produces smaller feature
sizes.
Process is slow and costly
Soft lithography
uses polymers and molds to
produce a patterned material. Sub-100 nm
patterns can be easily prepared at a much lower
cost than EBL
PDMS Stamps and soft lithography
A polydimethylsiloxane (PDMS) prepolymer is poured
on top of the master with a curing agent. Upon
heating, the PDMS hardens and can be used as a stamp
for further patterning.
Master can be
prepared by
photolithography,
EBL, or other
patterning
techniques
Microcontact printing (μCP)
Ink can be added to the PDMS stamp. The ink will coat
the surface of the stamp via weak intermolecular
interactions. Ink can then be pressed on a substrate to
pattern it with a thin layer of ink material.
Inks can be
fluorescent
biomolecules,
nanoparticles,
polymers, etc.
ideal for biomolecule patterning because
it can be done under neutral/almost neutral pH
and at room temperature.
elective deposition
– Slow reaction at the non-growth surface
(orange).
– Growth surface (blue) is a reactant.
– Reaction is facilitated by growth surface.
