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. 2019 Feb 20;5(2):eaat9934. doi: 10.1126/sciadv.aat9934

Fig. 2. Methodology validation by determining the spring constant of AFM tipless microcantilevers with known value.

Fig. 2

(A) Phase-contrast image showing the AFM cantilever with a 10-μm sphere (white dashed circle) and a tipless AFM cantilever with known stiffness. Scale bar, 45 μm. (B) Phase-frequency curves depicting frequency shifts acquired by keeping a constant π/2 phase (dotted line) when the acoustically vibrating cantilever with microsphere is moved from 1 μm to 50 nm from the tipless cantilever. (C) Determined AFM tipless cantilever spring constant using standard thermal fluctuations and novel noncontact FM-AFM methods. Data are presented as means ± SEM; NS indicates nonsignificant differences in comparison with controls, P = 0.14 (by unpaired two-tailed Student’s t test with Welch’s correction); numbers of measurements pooled were five tune curves for the thermal method and eight phase-frequency curves for the noncontact FM-AFM.