  Controlled transport of surface functionalized magnetic beads in a liquid
medium is a central requirement for the handling of captured biomolecular
targets in microfluidic lab-on-chip biosensors. Here, the influence of the
physiological liquid medium on the transport characteristics of functionalized
magnetic particles and on the functionality of the coupled protein is studied.
These aspects are theoretically modeled and experimentally investigated for
prototype superparamagnetic beads, surface functionalized with green
fluorescent protein immersed in buffer solution with different concentrations
of a surfactant. The model reports on the tunability of the steady-state
particle substrate separation distance to prevent their surface sticking via
the choice of surfactant concentration. Experimental and theoretical average
velocities are discussed for a ratchet like particle motion induced by a
dynamic external field superposed on a static locally varying magnetic field
landscape. The developed model and experiment may serve as a basis for
quantitative forecasts on the functionality of magnetic particle transport
based lab-on-chip devices.
