= Solution
In <quantitative nanomechanical mapping>, the operational <adhesion> is the magnitude of the most attractive <force> immediately before detachment on a calibrated retraction curve:
$$
F_{\rm adh}=-\min F_{\rm retract},\qquad F=k_c\delta_c.
$$
Here $k_c$ is the <cantilever spring constant> and $\delta_c$ its deflection after baseline subtraction. The area between approach and retraction relates to dissipated work, whereas the minimum <force> is a <force>, not an <energy>. Chemical attraction, <Van der Waals forces> and ambient-water capillary bridges can all contribute. Match loading rate and peak load, calibrate deflection sensitivity and $k_c$, compare clean reference surfaces, and control humidity; otherwise different maps may reflect different tips or capillary conditions rather than different specimens.
\Image[/past-exam-of-the-mphil-in-micro-and-nanotechnology-enterprise-course-of-the-university-of-cambridge/2019/paper-1-afm-contact.png]
{title=Original illustrative force-cycle schematic distinguishing pull-off force from dissipated work}
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