title: An on-chip micromagnet frictionometer based on magnetically driven colloids for nano-bio interfaces.
abstract: A novel method based on remotely controlled magnetic forces of bio-functionalized superparamagnetic colloids using micromagnet arrays was devised to measure frictional force at the sub-picoNewton (pN) scale for bio-nano-/micro-electromechanical system (bio-NEMS/MEMS) interfaces in liquid. The circumferential motion of the colloids with phase-locked angles around the periphery of the micromagnets under an in-plane rotating magnetic field was governed by a balance between tangential magnetic force and drag force, which consists of viscous and frictional forces. A model correlating the phase-locked angles of the steady colloid rotation was formulated and validated by measuring the angles under controlled magnetic forces. Hence, the frictional forces on the streptavidin/Teflon interface between the colloids and the micromagnet arrays were obtained using the magnetic forces at the phase-locked angles. The friction coefficient for the streptavidin/Teflon interface was estimated to be approximately 0.036 regardless of both vertical force in the range of a few hundred pN and velocity in the range of a few tenths of μm s(-1).
authors.affiliation: Department of Emerging Materials Science, DGIST, Daegu 42988, Republic of Korea. cgkim@digst.ac.kr.
authors.forename: Xinghao
authors.initials: X
authors.lastname: Hu
authors.forename: Sandhya Rani
authors.initials: SR
authors.lastname: Goudu
authors.forename: Sri Ramulu
authors.initials: SR
authors.lastname: Torati
authors.forename: Byeonghwa
authors.initials: B
authors.lastname: Lim
authors.forename: Kunwoo
authors.initials: K
authors.lastname: Kim
authors.forename: CheolGi
authors.initials: C
authors.lastname: Kim
mesh_terms: D003102:Colloids; D017276:Friction; D060526:Magnetic Fields; D055617:Micro-Electrical-Mechanical Systems; D055616:Microtechnology / Q000295:instrumentation*; D036103:Nanotechnology / Q000295:instrumentation*
chemical_list: D003102:Colloids