Measurement of sub-nanonewton forces inside a scanning electron microscope

Area of Science:

• Physics
• Materials Science
• Surface Science

Background:

• Adhesion is governed by van der Waals, electrostatic, and capillary forces at micro- and nanoscales.
• Existing techniques lack experimental insight into these forces below 10 nN, especially when capillary forces dominate.
• Understanding these interactions is crucial for numerous applications and research fields.

Purpose of the Study:

• To develop a novel interferometric force spectroscopy setup with sub-nanonewton resolution.
• To investigate the interplay of van der Waals, electrostatic, and capillary forces at small force ranges.
• To enable systematic experimental validation of adhesion theories on the micro- and nanoscale.

Main Methods:

• Integration of a scanning probe technique into a scanning electron microscope's vacuum chamber.
• Development of an interferometric force spectroscopy setup achieving sub-nanonewton resolution.
• Measurement of adhesion energies between a silica colloidal probe and a silicon substrate.

Main Results:

• The setup reliably measures adhesive interactions in both vacuum and ambient environments.
• Demonstrated sub-nanonewton resolution for force spectroscopy.
• Successfully conducted initial measurements of adhesion energies, paving the way for further studies.

Conclusions:

• The developed setup overcomes limitations in measuring small adhesion forces.
• It allows for the investigation of separate contributions of capillary, van der Waals, and electrostatic forces.
• Provides a platform for validating adhesion theories at the micro- and nanoscale.