Fig. 4: Bioinspired swimming and navigation within ex vivo biomedical environment.
a, Undulatory motion of the microbubble-array fins (12 μm, 16 μm and 66 μm in diameter, 50 μm in depth) of the bioinspired stingraybot before release. b, Forward swimming of the stringraybot under sweeping-frequency excitation (30–90 kHz, 2 s, 60 VPP). Right: fin motion during swimming. Lower inset: schematic of the patterned microbubble arrays. In a and b, the pink dashed lines and arrows denote the fin shapes in last step and the fin’s moving direction, respectively. c, Edible hydroxypropyl methylcellulose capsule (27 mm × 12 mm) containing a pre-folded stingraybot. d, Set-up for release and navigation of the encapsulated artificial muscle in an excised porcine stomach, with an external transducer positioned approximately 3 cm from the stomach and internal endoscope for visualization. e, Locomotion of the stingraybot inside an excised porcine stomach. f, Locomotion of a pre-folded, wheel-shaped artificial muscle (30 mm × 5 mm × 80 μm) with variable-size microbubble arrays (12 μm, 16 μm and 66 μm in diameter, 50 μm in depth) inside a porcine stomach. The artificial muscle propels along the stomach surface under sweeping-frequency excitation (30–100 kHz, 2-s sweep period, 60 VPP). The blue arrows mark the direction of motion and the green dots indicate the centre position. Inset: pre-folded shape. g, Set-up for ex vivo manipulation of a pre-folded artificial muscle inside an excised porcine intestine, with external transducers and an internal endoscope. Inset: endoscopic view of the artificial muscle. h, Time-lapse images showing the artificial muscle rolling along the curved mucosal wall under ultrasound sweeping-frequency (30–100 kHz, 2-s sweep period, 60 VPP) delivered by a piezo transducer. i, Locomotion of the artificial muscle driven by a high-intensity focused ultrasound transducer (1–3 MHz, 1-s sweep period, 60 VPP). Red lines, trajectory; yellow dots, centre position over time. Scale bars, 1 cm (a–c,e,f,h,i), 2 cm (d,g).
