Hardware Reference
In-Depth Information
Chapter 6
Pin-Count Minimization
for Application-Independent Chips
In this chapter, we propose design methods for pin-limited general-purpose
microfluidic biochips. The number of control pins used to drive electrodes is a major
contributor to fabrication cost for disposable biochips in a highly cost-sensitive
market. Most prior work on pin-limited biochip design determines the mapping
of a small number of control pins to a larger number of electrodes according to
the specific schedule of fluid-handling operations and routing paths of droplets.
Such designs are therefore specific to the bioassay application, hence sacrificing
some of the flexibility associated with digital microfluidics. We propose a design
method to generate an application-independent pin-assignment configuration with
a minimum number of control pins. Layouts of commercial biochips and laboratory
prototypes are used as case studies to evaluate the proposed design method for
determining a suitable pin-assignment configuration. Compared with previous pin-
assignment algorithms, the proposed method can reduce the number of control pins
and facilitate the “general-purpose” use of digital microfluidic biochips for a wider
range of applications.
6.1
Motivation and Related Prior Work
In recent years, the complexity of digital microfluidic biochips continues to increase
as new applications are targeted by this platform [
1
,
2
]. For example, recently
announced commercial products contain up to 100,000 electrodes [
3
]. In order
to ensure complete reconfigurability and the ability to run any given bioassay
on the digital microfluidic platform (i.e., “general-purpose use”), it is desirable
that every electrode be controlled by an independent pin. However, a one-to-one
mapping between control pins and electrodes (referred to as direct-addressing pin-
assignment) is not practical for low-cost disposable biochips. A large number of
control pins leads to high fabrication cost, and interconnect routing problems [
4
].
