Accurate Calibration and Uncertainty Estimation of the Normal Spring Constant of Various AFM Cantilevers

Abstract

Measurement of force on a micro- or nano-Newton scale is important when exploring the mechanical properties of materials in the biophysics and nanomechanical fields. The atomic force microscope (AFM) is widely used in microforce measurement. The cantilever probe works as an AFM force sensor, and the spring constant of the cantilever is of great significance to the accuracy of the measurement results. This paper presents a normal spring constant calibration method with the combined use of an electromagnetic balance and a homemade AFM head. When the cantilever presses the balance, its deflection is detected through an optical lever integrated in the AFM head. Meanwhile, the corresponding bending force is recorded by the balance. Then the spring constant can be simply calculated using Hooke’s law. During the calibration, a feedback loop is applied to control the deflection of the cantilever. Errors that may affect the stability of the cantilever could be compensated rapidly. Five types of commercial cantilevers with different shapes, stiffness, and operating modes were chosen to evaluate the performance of our system. Based on the uncertainty analysis, the expanded relative standard uncertainties of the normal spring constant of most measured cantilevers are believed to be better than 2%.

Influence of Cell Surface and Nanomechanical Properties on the Flocculation Ability of Industrial Saccharomyces cerevisiae Strains

“…The yeast samples were imaged in contact mode (CM) by using Si 3 N 4 (silicon nitride) triangular cantilevers (Veeco, Santa Barbara, CA, USA). The Si 3 N 4 cantilever's spring constant was calibrated systemically using the thermal tune method (Song, Wu, Xu & Fu, 2015) and was found to be in the range of 0.01 -0.02N/m. All the images (512×512 pixels) were captured at room temperature with a scanning speed of 0.5µm/sec and an applied force of 0.1nN.…”

Displacement Measurement Method Based on the Rotating Paraboloid Array

“…On the one hand, non-optical displacement measurement methods include capacitance measurement and inductance measurement [13,14]. On the other hand, laser triangulation [15], optical levers [16], grating displacement measurement [17], fiber displacement measurement [18], and laser interferometry [19] belong to the optical displacement measurement methods. The capacitance measurement method can achieve high measurement resolution, but its range is shorter, generally less than 1 mm [20].…”

Global sensitivity analysis of backside coating parameters on dynamic response of AM-AFM

“…Various coatings are used depending of applications [8,9,12,13]. Different methods of calibration have been proposed where the effect of backside coating is omitted [3,[14][15][16], however some attempts were done by assuming the coating as an inelastic body for calibration of AFM cantilever [7].…”