W. Richard Bowen and Nidal Hilal 4

Force (nN m –1 )
Loading force
(mN m –1 )
52
55
61
5.3 MODIFICATION OF MEMBRANEs 151
Separation (nm)
fIgurE 5.6 Representative approach (grey) and retraction (black) force curves of
BSA-modified colloid probe to grafted membrane with qDMAEMA at different loading
forces (pH 7).
5.3.3 (bio)Adhesion forces between a bSA-functionalised
Colloid Probe and Membrane Surface
Adhesion force measurements were performed using the colloid probe
technique. Colloid probes were prepared by immobilising modified
microsphere with BSA to a tipless ultralever silicon cantilever.
Examples of retraction curves measured at three different loading
forces for a BSA-modified microsphere interacting with a PES membrane
grafted with qDMAEMA, shown in Figure 5.6, demonstrate that the adhesion
force (pull-off force) increases with the force applied via the colloid
[20]. Similar findings have been observed in previous studies [7, 14]. The
increase in the adhesion force is most likely to result from an increase in
the number of chemical bonds formed between the biopolymers when the