The Problem
High throughput screening is a standard method used in drug
discovery for testing potential active ingredients and also for
conducting bio-assays. A major programme of research in
pharmaceutical companies is aimed at miniaturising the assay
systems so that they can operate on micron dimension samples to
reduce the amount of material required and so speed up the overall
drug discovery process. This work includes the development of
micron scale equipment for fluid handling and for detection. An
essential feature of these developments is the modelling of fluid
flow in such micron scale systems.
The Challenge
Conventional fluid dynamics codes are not applicable to
microfluidic modelling because, inter alia, the assumption of zero
velocity at the wall is invalid. Daresbury computational science
and engineering group turned their attentions to this generic
problem in 1999 when the 'Centre for Microfluidics and Microsystems
Modelling' (C3M) was established. The resulting modular code
(µTHOR) has been proved in numerous applications from bubble
transport to microchannel flow modelling in complex geometries. In
particular, the development of microassay systems depends
critically on the leading edge capability of µTHOR to simulate a
wide range of geometries and material properties and hence to
identify designs that operate effectively in ultra high throughput
processes.
The Solution
C3M has performed computational microfluidic dynamics
simulations on the proposed assay systems across a wide range of
design parameters, including flow rates, channel dimensions,
intersection geometries, fluid properties and reagent
concentrations. This has extended to areas such as mixers, pumps,
electro-kinetic and magneto-hydrodynamic transport, two-phase flow
and design optimisation. This has been critical in identifying
design preferences and thereby focusing the experimental
developments. The success of the approach has led to the design of
biosensing microtitre plates which permit up to 1536 screening
assays to be performed simultaneously, compared with just four
using current technology, and leading to massive acceleration of
the drug discovery process.
Electric field strength in x-direction
Stream function contours
The Benefits
- The ability of µTHOR to accommodate both geometric designs and
the physical properties of the fluid materials in combined
simulations allowed the modelling of complete devices in
operation
- The successful modelling of a wide range of device structures
and operating conditions significantly reduced the experimental
programme with attendant cost savings in the research project
- The ability to construct massively parallel bio-assay devices
will deliver both significant cost savings and reduced candidate
identification times in drug discovery programmes.