Figure 3: Recognition between targets by using feedback-type optical actuation.
(a) Schematic drawing of the geometry of the flytrap gripper. (b) Change in gripping angle |dα| as a function of distance d at different output powers P (points and lines are experimental and calculated data, respectively). Inset: photograph of the closed gripper with a maximum value in |dα|. Error bars indicate the imaging system accuracy (4°) in every single measurement. (c) Measured bending ratio dα/dαmax as a function of input power P for targets with high (R=90%) and low (R=3%) reflectivity. Insets: photographs of the gripper at its closed and open stages when meeting high-reflectivity and low-reflectivity targets, respectively (power 67 mW in both cases). (d) Measured bending ratio dα/dαmax as a function of input power P for a glass micro-sphere (R=90%), a highly absorbing (R<1%) and highly scattering PDMS targets. Insets: photographs of the closed gripper meeting different targets with different threshold powers: 44 mW for the micro-sphere, 73 mW for the scattering and 69 mW for the absorbing target. The error bars in c and d indicate the imaging system accuracy (4°) plus the s.d. for n=3 measurements. All scale bars correspond to 5 mm. An optical filter is used to block wavelengths below 500 nm for all the photographs.
