Tech Briefs Magazine - October 2023 - Comsol-12A

RESEARCH SPOTLIGHT
FIGURE 4 Left: A flow-optimized microchannel design. Right: A reaction-optimized
microchannel design, which features a mix of primary " arteries " and secondary
" capillaries " . The arteries sustain overall flow toward the outlet, while capillaries enable
broader reactant distribution toward the electrode. In both cases fluid flows from the inlet
at the upper left to the outlet at the lower right.
designs have followed a few familiar patterns. More complex
forms could improve performance, but increasing a design's
complexity adds to the time needed to define, fabricate, test,
and adjust that design.
Zhou and his colleagues recognized that before trying
to optimize their designs, they first had to optimize their
design process. To generate a higher-performing formal
solution to their problem, the team created their simulationdriven
inverse design methodology. Their methodology does
not define forms in advance of testing, but rather sets key
parameters and then directs algorithms to generate forms
that fulfill those parameters.
" We were seeking an efficient way of approximating what
a more complex simulation would show. We have sacrificed
some modeling complexity, which actually enables us to
explore more elaborate designs in less time, " Zhou says. " Some
people use topology optimization for problems like this, and
12a COMSOL NEWS
they come up with designs
that maybe have 10 channels.
This is because they are asking
their algorithm to determine
the exact placement of every
physical element of the
channels in advance, which
requires a lot of computing
power and time to achieve a
complex design, " he explains.
» FROM DESIRED
RESULTS TO NOVEL
FORMS, FASTER
So how could the TRINA
team use its methodology to
efficiently generate better
microchannel designs? First,
they simulated idealized
flow trajectories through
the effective anisotropic
porous material, then
they extracted values that
described the idealized fluid
behavior. Next, they input
those values into another
simulation, which generated
the microchannel forms that
would cause that behavior.
Essentially, they defined the
effect they wanted their
designs to produce before
designing anything.
Zhou explains, " Our
COMSOL model of the
porous material has only
two material values and
a very coarse mesh. We
implement a sensitivity-based
optimization process based on
Navier-Stokes and advection-
reaction-diffusion equations.
We assume steady-state,
incompressible, and laminar
fluid flow through the porous
media, and that the desired
chemical reactions will occur
proportionally to the reactant
concentration. We run these
simulations to arrive at an
optimal distribution of fluid
flow orientation through the
pores. This process gives us
valuable results with a huge
reduction in computational
complexity. "
Zhou describes this part of
the overall design process as
homogenization. Having now
established a pattern of ideal
trajectories of fluid through
the plate's pores, the next
step is dehomogenization.
This step involves the
equation-driven definition of
microchannel forms that will
force fluid to follow these
optimal paths.
» GENERATED DESIGNS
THAT MAXIMIZE FLOW,
REACTION, OR BOTH
The dehomogenization step
is needed, Zhou says, because
" we cannot fabricate an ideal
porous material with each

Tech Briefs Magazine - October 2023

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