<p>Microparticles
have been investigated not only as feedstock spherical or amorphous bulk
materials used for shape molding, but also as agents that can perform work in
the micron scale. The fabrication of microparticles with active properties of
self-propulsion, self-assembly, and mobility with enhanced mechanical, thermal,
and chemical properties is of particular interest for emerging technologies
such as drug delivery, micro-robotics, micro energy generation/harvesting, and
MEMS. Conventional fabrication methods can produce several complex particle
shapes in one fabrication session or hundreds of spheroid shaped particles per
second. Innovative techniques, as flow lithography, have demonstrated control
over particle form and composition for continuous fabrication cycles. In recent years predefined shape polymer microparticles have been
fabricated as well as ceramic microparticles through suspension processing with
these set of techniques. Even though ceramic materials have been fabricated,
there is still a strong need to increment the palette of available materials to
be processed via flow lithography. We have pioneered the production of shaped
ceramic microparticles by Stop-Flow Lithography (SFL) using
preceramic polymers, providing control of particle size and shape in the range
of 1 – 1000
μm. The principal arranged technique (SFL) combines aspects of
PDMS-based microfluidics and photolithography for the continuous cyclable fabrication
of microparticles with predefined shapes. The PDMS microchannel devices used
were fabricated with vinyl film molds in a laminar hood avoiding the need for a
cleanroom, procedure that reduced fabrication costs. After a fabrication
session, the preceramic polymer microparticles were collected, washed, and
dried before entering an inert atmosphere furnace for pyrolysis. Additionally, by treating the material initially as liquid polymer,
special properties can be added by converting it into an emulsion or a
suspension. Microparticles
were functionalized by introducing porosity and magnetic nanoparticles in the
preceramic polymer matrix. The porous characteristic of a particle leads to an
increase in surface area, allowing the particle to be infiltrated with a
catalyzer or act as a chemical/physical carrier, and the magnetic behavior of
the particles allows a controllable trajectory with defined external magnetic
fields. These two properties can be used to fabricate bifunctional
microparticles to serve as drug carriers through human arteries and veins for drug delivery purposes.
We
successfully fabricated solid and functional ceramic microparticles in the 10 – 50
μm range with predefined shapes as hexagons, gears, triangles, and ovals. This
system is an economical route to fabricate functional defined shape particles
that can serve as microrobots to perform tasks in liquid media.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12210278 |
| Date | 30 April 2020 |
| Creators | Alejandro Manuel Alcaraz Ramirez (7469432) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/FABRICATION_OF_SOLID_POROUS_AND_MAGNETIC_CERAMIC_MICROPARTICLES_VIA_STOP-FLOW_LITHOGRAPHY/12210278 |
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