Measurement of the complete interaction force curve at the nanoscale

TL;DR

The paper introduces the Force Feedback Microscope (FFM), a novel AFM technique that enables complete, high-sensitivity measurement of interaction force curves at the nanoscale, overcoming previous contact limitations.

Contribution

The FFM provides a simple yet effective control paradigm allowing continuous force curve measurement, including attractive interactions, with sub-piconewton sensitivity.

Findings

Successfully measured complete interaction force curves.

Demonstrated real-time detection of water bridge nucleation.

Achieved high sensitivity in force measurement.

Abstract

The force between two interacting particles as a function of distance is one of the most fundamental curves in science. In this regard, Atomic Force Microscopy (AFM) represents the most powerful tool in nanoscience but with severe limits when it is to probe attractive interactions with high sensitivity. The Force Feedback Microscope (FFM) described here, removes from AFM the well known jump to contact problem that precludes the complete exploration of the interaction curve and the study of associated energy exchanges. The FFM makes it possible to explore tip-surface interactions in the entire range of distances with a sensitivity better than 1 pN. FFM stands out as a radical change in AFM control paradigms. With a surprisingly simple arrangement it is possible to provide the AFM tip with the right counterforce to keep it fixed at any time. The counterforce is consequently equal to the tip-sample force. The force, force gradient and damping are simultaneously measured independently of the tip position. This permits the measurement of energy transfer in thermodynamic transformations. Here we show some FFM measurement examples of the complete interaction force curve and in particular that the FFM can follow the nucleation of a water bridge by measuring the capillary attractive force at all distances, without jump to contact despite the large attractive capillary force. Real time combination of the measured parameters will lead to new imaging modalities with chemical contrast in different environments.