Interfacial Force Microscope
Qunyang Li
Carpick Group
Interfacial Force Microscope (IFM)
Capable of measuring normal and lateral forces between a probe and
sample. Functions much like an AFM or a nano-indenter.
A few features make it different:
The force sensor has zero compliance (i.e. infinitely stiff), therefore
loading is through a displacement-controlled process
o The probe can (or has to) be made by users and mounted to the
force sensor
o The typical force sensor has a measuring range of 10 nN ~ 50 µN
(resolution better than 1nN), lying between conventional AFM and
nano-indenter; displacement resolution better than 1 Å
o Measurement environment (e.g. humidity) is potentially controllable
IFM System
Controller
Computer
Head & sample stage
IFM Probes and Sensors
sample
probe
Probe mounted ona sensor
Force sensor:
A novel electrostatically-driven & self-
balancing sensor, which ALWAYS
maintains at the same position Sample
Probe TipTorsion Bars
C2 C1
ZERO instrument compliance
Unique Feature
Because of zero machine compliance, there is no “snap-in” or “snap-out” of contact when we perform force-distance measurements.
Without feedback Without feedback
Joyce, S. A. and J. E. Houston (1991). Review ofScientific Instruments 62(3): 710-715
Typical Measurement of IFM
0 100 200 300 400 500 600 700-30
-20
-10
0
10
Fo
rce
( µN
)
Displacement (nm)
approaching retracting
Probe: Spherical silica tip (a few hundred microns in radius) made bypulling borosilicate glass capillary tube under H2 flame;
Substrate: Silica flat made by thermally oxidizing a silicon wafer.
Not accessibleby AFM
N2 environment with 20% relative humidity
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