1 Supporting information On-Chip Micromagnet Frictionometer Based on Magnetically Driven Colloids for Nano-Bio Interface Xinghao Hu , Sandhya Rani Goudu , Sri Ramulu Torati, Byeonghwa Lim, Kunwoo Kim, CheolGi Kim * Department of Emerging Materials Science, DGIST, Daegu 42988, Republic of Korea These authors contributed equally to this work. *Corresponding author: cgkim@dgist.ac.kr Electronic Supplementary Material (ESI) for Lab on a Chip. This journal is © The Royal Society of Chemistry 2016