AG Jacobs

AFM, FastScan Bio by Bruker

Operating Modes:

ScanAsyst in Air/Fluid
Tapping Mode in Air/Fluid
Contact Mode in Air/Fluid
Lateral Force Microscopy
Nanomechanical Mapping (PeakForce QNM)
Force Volume
Electrical & Magnetic Lift Modes

Sample Specifications:

Max. diameter ca. 20 cm, thickness: max. 1.2 cm
Maximum scan range: 90 μm x 90 µm in air, 30 µm x 30 µm in liquid
Maximum scan height: ca. 3 µm

Applications:

We use highly compressed hydroxyapatite pellets as a first order model system for the mineral phase of tooth enamel. These pellets, when properly prepared, feature locally a very low surface roughness below 1 nm (rms). Upon etching (e.g., as a part of a cleaning procedure), domains become visible due to different etching rates of differently oriented crystallites.

AFM height scans of a polished and etched hydroxyapatite surface. The step like structures (domains) in the left panel become visible upon etching for a few seconds in an acidic buffer (pH 4.5). The rms roughness on a single domain is typically below 1 nm.

With the FastScan Bio, we are also able to map mechanical surface properties or adhesion forces. Adhesion force maps of hydroxyapatite surfaces reveal different forces on different grains. However, the origin of these differences is yet unknown and its exploration is part of our ongoing research.

Adhesion force map of a hydroxyapatite surface recorded with a diamond like carbon coated AFM tip in air.