In considering the adhesion of functionalized particles to surfaces, the role of several features contributing to the interplay between hydrodynamics, surface forces and specific interactions can be sorted out through a hierarchy of interfacial and hydrodynamic flow experiments.

In this paper, we report on the direct measurements on a molecular system designed to allow targeted deposition and binding of particles to cellulose. This system involves a family of heterobifunctional fusion proteins that bind to both a red dye and to cellulose with various affinities. Amine-coated particles are labeled with a red dye, and the fusion protein is attached to these particles in various number densities. The strength of adhesion of a single particle to a cellulose fiber is measured by using micropipette aspiration as a function of adhesive affinity and specificity of the protein, its surface density and contact time. In addition, the dynamics of adhesion of the functionalized particles to cellulose-coated glass slide under controlled hydrodynamic flow is explored using flow chamber assays for two scenarios: detachment of bound particles, and attachment of particles in suspension, as a function of shear rate in addition to above mentioned parameters. Highly specific adhesion is observed in both studies, with a strong dependence on all of the operating variables. The force of adhesion was ~ 2 nN for the particles that were fully functionalized with bifunctional protein with the frequency of adhesion > 90% in micropipette aspiration experiments, while average force required to detach a bound particle was ~ 125 pN in flow chamber assays.