Fig. 5

Mechanical properties of the asters. a A 7-μm silica sphere is attached to an AFM tip to probe the single asters; the indentation curves (black) can be fitted by the Hertz model, giving E (Young’s modulus) ~6 kPa. Small hysteresis of the retraction curves (gray) suggests a finite energy dissipation. Sometimes we observe negative forces during retraction (the right curve), reflecting adhesion of the tip sphere to the aster. The two curves are horizontally shifted for clarity. b E drops significantly when the probed location is moved from the center to periphery (from blue to red). c Dependence of E as a function of d/R. Points are experimental data and black curve is the fitting by the analytical function in the main text. The inset displays geometry of AFM measurements. d Schematic representation of ribbon deformation under force. e An aster sector is reversibly bent by an optical tweezer. The silica sphere is 10 μm in diameter. f Shear moduli (G′ and G″, black and gray points, respectively) of the aster precipitate phase (1 mg/ml) measured by a rheometer. g Variation of G′ as a function of surfactant concentration