Minimizing the number of external control pins is one of the most important optimization objectives in digital microfluidic biochip (DMFB) designs especially as the chip size gets even bigger. So far, only few works focus on this issue for general-purpose DMFBs. In this paper, we present a pin count minimization algorithm based on sophisticated electrode chaining on regular or irregular electrode arrays. The key idea of the proposed method is that actuation information can be implied from previous neighborhood electrodes to later ones throughout a chain. Experimental results show that the pin count reduction can be near 50% in large DMFBs.