two step Berkeley Lab process enables covalent attachment
of the monolith to the channel walls and dramatically
enhances the adhesion - a result no other method has been
able to achieve.
reacting, separating, and
compounds in systems involving:
and peptide mapping
of chemical and biological agents
solid phase extraction (SPE)
analysis and monitoring
Allows use of plastic chips mass produced via inexpensive
voids at the monolith/channel interface
undesirable adsorption of processed compounds at the channel
and accelerates functionalization via UV initiated grafting
consumption of precious or custom prepared monomers
monomers with almost any chemistry
increases the surface density of functionalities
spatial control of functionalization within the microchannels
Fréchet, Frantisek Svec, and Thomas Rohr have used
photoinitiated grafting to develop plastic microfluidic substrates,
place porous polymer monoliths within the channels, and modify
the pore surface of these monoliths to improve device performance.
The Berkeley Lab researchers have overcome the undesirable
absorption characteristics typical of the microchannel surfaces
in thermoplastic chips by using simple UV triggered functionalization,
eliminating the major obstacle to commercial development of
these chips. Polymeric microfluidic substrates are advantageous
because they can be fabricated using inexpensive techniques
such as injection molding or hot embossing instead of the
expensive multistep wet fabrication that is required to produce
chips from inorganic substrates.
A technology developed earlier by Fréchet, Svec, and
colleagues entails the fabrication of porous polymer monoliths
within microfluidic channels using photoinitiated polymerization.
This process uses a photolithographic technique - irradiation
through a mask - to prepare the monolithic polymer only in
desired areas of the microchannels. The present invention
expands the use of UV radiation and masking to graft functionalities
to both the channel walls and the polymer monolith. Although
photografting has been used for two dimensional flat surfaces
before, the Berkeley Lab group is the first to demonstrate
its use for three dimensional highly crosslinked porous polymers,
which were assumed to be too opaque or diffractive for the
Photoinitiated grafting allows tailoring of surface chemistry
in specific locations of the porous monolith. This spatial
control of functionality is very difficult to achieve with
non-grafting techniques currently in use such as direct copolymerization,
classical chemical modification, or with grafting initiated
by means other than UV light.
Modifying and functionalizing the surface of the microchip
via photoinitiated grafting (i) makes the wall non-adhesive
for the processed compounds and (ii) prevents formation of
voids at the monolith/channel interface, thus improving the
overall performance of the device. The two step process enables
covalent attachment of the monolith to the channel walls and
dramatically enhances the adhesion - a result no other method
has been able to achieve. In addition, grafting chains of
functional polymers to the active sites at the surface of
pores within the monolith allows multiple functionalities
to emanate from each site and leads to a significant increase
in the number of functionalities.
The Berkeley Lab UV initiated grafting technique is mediated
by hydrogen abstracting photoinitiators and can be used with
all materials that have sufficient UV transparency. The process
also enables the consecutive grafting of monomers onto the
monoliths pore surfaces to create layered chemistries.
- Issued Patent # 7,431,888. Available for licensing or collaborative research.
T., Ogletree, F.D., Svec, F., Fréchet, J.M., Photografting
and the Control of Surface Chemistry in Three-Dimensional
Porous Polymer Monoliths, Macromolecules 2003,
T.B., Rohr, T., Hilder, E.F., Peterson, D.S., Yi, M., Svec,
F., Fréchet, J.M., "Fabrication of Porous Polymer
Monoliths Covalently Attached to the Walls of Channels in
Plastic Microdevices, Electrophoresis 2003, 24,
Rohr, T., Svec, F., Fréchet, J.M., Dual-Function
Microanalytical Device by In Situ Photolithographic Grafting
of Porous Polymer Monolith: Integrating Solid- Phase Extraction
and Enzymatic Digestion for Peptide Mass Mapping, Anal.
Chem. 2003, 75, 5328-35.
Rohr, T., Ogletree, F.D., Svec, F., Fréchet, J.M.,
Surface Functionalization of Thermoplastic Polymers
for the Fabrication of Microfluidic Devices by Photoinitiated
Grafting, Adv. Funct. Mater. 2003, 13, 264-70.
THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD: