Hardware Reference
In-Depth Information
In addition to errors in fluid-handling operations, another possible cause for the
failure of a bioassay is the uncertainty in the completion time of fluid-handling
operations. Due to the inherent randomness of biochemical reactions, the time
required to complete each step of the bioassay can be viewed as a random variable.
To address this issue, a new “operation-interdependence-aware” synthesis algorithm
is proposed in this research work. The start and stop time of each operation are
determined by feedback from the on-chip sensor. Bioassays can therefore be carried
out in a self-adaptive fashion on cyberphysical microfluidic biochips. With such a
synthesis approach, the reliability and flexibility of the biochips are improved, and
the applications of biochips can be extended beyond well-calibrated bioassays to the
exploration of new biochemical protocols.
To reduce the cost of fabricating biochips while maintaining flexibility with
respect to potential applications, the concept of a general-purpose pin-limited
biochip is introduced in this topic. Using a graph model for pin-assignment, we have
constructed the theoretical basis and a heuristic algorithm to generate optimized
pin-assignment configurations. The associated scheduling algorithm for on-chip
biochemistry synthesis is also presented. A complete design flow for pin-limited
cyberphysical microfluidic biochips is presented on the basis of these results.
Another design problem addressed in this topic is a layout-design algorithm that
can minimize the interference between the devices on a biochip. A probabilistic
model for the polymerase chain reaction (PCR) process is considered; based on
the model, the control software can make on-line decisions regarding the number of
thermal cycles that must be performed in the PCR procedure. Therefore, the duration
of the PCR can be precisely controlled.
The rest of this chapter is organized as follows. Section
1.1
presents an overview
of digital microfluidics. Section
1.2
introduces the design automation aspects of
digital microfluidic biochips. Section
1.3
presents a chapter-by-chapter outline for
this topic.
1.1
Overview of Digital Microfluidics
In this section, we present an overview of digital microfluidics, including the theory
of electrowetting-on-dielectric, the hardware platform, sensing techniques, and fault
models for biochips.
1.1.1
Theory of Electrowetting-on-Dielectric
The electrowetting effect has been defined as “the change in solid-electrolyte
contact angle due to an applied potential difference between the solid and the
electrolyte” [
11
]. A detailed analysis of this phenomenon is presented in this section.
