The advent of atomic force microscopy(AFM)provides a novel powerful tool for addressing biological issues in their native states.AFM uses a sharp tip mounted at the end of a micro-fabricated cantilever to probe the specimens immobilized on the support.Compared with other high-resolution imaging and mea-surement techniques(e.g.super-resolution optical microscopy,scan-ning electron microscopy,transmission electron microscopy,and magnetic/optical tweezers),the unique merit of AFM is that it is able to simultaneously acquire the structures and properties of living biological samples under aqueous conditions with unprece-dented spatiotemporal resolution(nanometer spatial resolution and millisecond temporal resolution)[1],making AFM an invalu-able platform for revealing the underlying mechanisms guiding life activities.The wide applications of AFM in molecular and cell biology provide considerable novel insights into the physi-ological/pathological processes[2].Particularly,in recent years,a new AFM imaging mode,which is called peak force tapping(PFT)mode[3],emerges as a promising way for correlating the topography of the specimens with the mechanics of specimens.In PFT mode,the vibrating AFM tip indents the sample at each sam-pling point to record force curves,and the peak force of the force curve is used as the feedback[4].By analyzing the force curves,several types of mechanical properties of the specimens can be real-timely visualized,and thus PFT mode is also called multiparametric imaging AFM[5],offering novel possibilities for resolving the fine structures and properties of fragile biological specimens.
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