Recently, digital microfluidic biochips (DMFBs) have revolutionized many biochemical laboratory procedures and received much attention due to their advantages such as high throughput, automatic control, and low cost. To meet the challenges of increasing design complexity, computer-aided-design (CAD) tools have been involved to build DMFBs efficiently, where a two-stage design flow of fluidic-level synthesis followed by chip-level design are generally applied. Regarding fluidic-level synthesis, many related studies and CAD tools have been well-developed to synthesize the fluidic behaviors efficiently and effectively. However, research findings being highly-concerned with the chip-level design are still critically lacking. In this paper, we shall focus on chiplevel design and discuss related background and two major optimization problems posed by electrode addressing and control pin routing. We show how CAD tools are involved to automate and optimize the two design problems. With this assistance, users can concentrate on the development and abstraction of nanoscale bioassays while leaving chip optimization and implementation details to CAD tools.