Fig. 3.

Mechanical characterization, in vivo deployment, and ex vivo evaluation of the flower-like prototype. (A) Schematic depicting transformable folded and expanded configurations and corresponding recoiling forces of the elastic elements (F_cr^Elastollan) and the nitinol springs (F_cr^nitinol). The dimensions of the prototype are shown in millimeters.Fnitinol cr for nitinol springs with a wire diameter φ = 0.5 mm reported for differing number of coils (n) and coil diameters (d) in (B). The dashed black line represents F_cr^Elastollan ¼ 0:4 N for a given dimension of the prototype. The blue area represents the experimentally observed valid design space. (C) In vivo endoscopic images of the prototype in pig’s esophagus in different configurations: (i) folded, (ii) deployed in direct and reverse directions, and (iii) folded after administration of 100 ml of 55°C water. (D) Radiograph and (E) histology results indicating penetration and dissolution of millineedles. (F) IVIS (in vivo imaging system) visualization of millineedle-administered dextran fluorescence in esophageal tissue. The control needle was devoid of dextran. The inset shows the optical image of the penetration sites highlighted with white circles. (G) Concentration of budesonide delivered to the esophageal tissue for n = 3 prototypes [each prototype is shown by a different color and consisted of one control needle (triangle) and three drug-loaded needles (circles)]. The inset shows a millineedle loaded with 0.1 mg of budesonide at the tip.