W. Richard Bowen and Nidal Hilal 4

4.3 CORREsPONdENCE bETwEEN sURFACE PORE dIMENsIONs FROM AFM ANd MwCO 113
F/R [mN/m]
–30
0 200 400 600 800
Piezo displacement [nm]
is more difficult than for colloid or modified colloid probes as the cell can
distort during the measurements. However, the data show that the XP117
development membrane has lower adhesion, and hence lower fouling
propensity, also for yeast cells.
4.3 CORRESPOnDEnCE bETWEEn SURFACE PORE
DIMEnSIOnS FROM AFM AnD MWCO
From a practical point of view, the choice of ultrafiltration membranes
for a particular process is usually defined in terms of MWCO, defined
such that solutes of such molecular weight would be 90% rejected by the
30
20
10
0
–10
–20
Modified membrane (2)
Conventional membrane (1)
FIgURE 4.6 SEM image of a BSA-coated silica sphere attached to a tipless AFM cantilever
and force versus piezo displacement plot (retraction) for two membranes in 10 �2 M
NaCl solution at pH 5.0 (conventional, ES404; modified, XP117).
Force [nN]
20
15
10
5
0
–5
C
B
Conventional membrane (1)
Modified membrane (2)
–10
0 100 200 300 400 500
Piezo displacement [nm]
FIgURE 4.7 SEM image of a yeast cell (Saccharomyces cerevisiae) attached to a tipless
AFM cantilever – a cell probe – and force versus piezo displacement plot (retraction) for
two membranes in 10 �2 M NaCl solution at pH 5.0 (conventional, ES404; modified, XP117).