Fig. 4.
Analysis and force measurements in the rigid adhesion system for different 3D geometries. (A) A schematic of the rigid adhesion system being pulled off from a spherical substrate under a negative pressure differential. Blue arrows indicate the direction of reaction force (Fr). (B) Calculated reaction force (Fr) profiles on a flat glass surface versus retraction distance (zr) for various initial pressures (ΔPo). (C) Calculated pull-off force (Foff) as a function of diameter (db) of glass spheres for various thicknesses (h0) (I), and Young’s moduli (Em) (II). (D) Calculated pull-off force (Foff) as a function of diameter (db) of glass spheres for various works of adhesion (ωad) (I) and initial pressures (ΔPo) (II). In all of these plots, the default parameter values are h0 = 0.2 mm, Em = 2.1 MPa, ωad = 4.0 J·m−2, and ΔPo = 0 kPa. (E) Measured reaction force profiles on a flat glass surface with respect to retraction distance, depending on different initial pressures. (F) Measured pull-off forces on glass substrates with different curvatures depending on the initial pressures. Each point indicates an average of five measurements, and error bars are ±1 SD.