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Atomic Force Microscopy

Atomic Force Microscopy

Atomic force microscopy (AFM) is a type of scanning probe microscopy that can analyze topographic details of various specimens like ceramics, glass, polymers, and biological samples. AFM offers over 1000 times more resolution than the optical imaging system. Images generated from AFM are three-dimensional surface profiles, offering an advantage over the flat, two-dimensional images from other imaging techniques.
The AFM Probe
The probe is regarded as the heart of any AFM setup and comprises the...

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Updated: Jun 12, 2026

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

Published on: February 27, 2015

Water sorption induced transformations in crystalline solid surfaces: characterization by atomic force microscopy.

Dabing Chen¹, Greg Haugstad, Zheng Jane Li

¹Department of Pharmaceutics, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, USA.

Journal of Pharmaceutical Sciences

|June 25, 2010

Summary

This summary is machine-generated.

Water adsorption on anhydrous theophylline crystals forms a surface solution, increasing molecular mobility and mediating solid-state transformation to theophylline monohydrate. This study visualizes surface changes using atomic force microscopy.

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Last Updated: Jun 12, 2026

Investigating Single Molecule Adhesion by Atomic Force Spectroscopy

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Published on: February 27, 2015

Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy

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Published on: May 27, 2018

Area of Science:

Solid-state chemistry
Materials science
Physical chemistry

Background:

Understanding solid-state phase transformations is crucial for material stability and performance.
Water sorption significantly influences the properties and reactivity of crystalline solids.
Theophylline serves as a model compound for studying anhydrate-to-hydrate transitions.

Purpose of the Study:

To investigate the role of water sorption in the solid-state transformation of anhydrous theophylline to its hydrate.
To elucidate the mechanism of hydrate formation mediated by surface mobility.
To determine the critical water activity thresholds for transformation.

Main Methods:

Atomic Force Microscopy (AFM) in contact and dynamic (tapping) modes to visualize surface topography and dynamics.
Polarized Light Microscopy to observe phase propagation.
Determination of transition relative humidity (RH(T)) and deliquescence relative humidity (RH(0)).

Main Results:

The transition water activity (RH(T)) was determined to be 62%, and deliquescence relative humidity (RH(0)) was 99% at 25°C.
AFM revealed increased surface mobility and suggested solution formation above RH(T).
Direct visualization of surface step movement confirmed enhanced mobility below RH(0), and hydrate phase propagation was observed.

Conclusions:

Solid-state transformation of anhydrous theophylline to theophylline monohydrate is mediated by a surface solution formed upon water adsorption.
Atomic Force Microscopy provides direct evidence for water-mediated solid-state phase transitions.
Surface mobility enhancement by thin solution films plays a key role in hydrate formation.