Fig. 3: Performance of Marangoni hydrogel rotors.
From: High-performance Marangoni hydrogel rotors with asymmetric porosity and drag reduction profile
a High-speed camera images of a characteristic rotor (r = 250 µm, h = 474 µm and n = 8) during its rotation. Small yellowish circles are used to mark the rotation position of the rotor. b The motion track of the hydrogel rotor within 60 ms. c–e The relationships between the maximum rotation speed Wmax, lifetime and geometric parameters of hydrogel rotor. The thickness h and teeth number n remain unchanged at 474 µm and 8 in (c), respectively. The radius r and teeth number n remain unchanged at 1000 µm and 8 in (d), respectively. The radius r and thickness h remain unchanged at 1000 µm and 551 µm in (e), respectively. Black circles are Wmax, red squares are lifetime. Error bars denote the standard deviation of the measurements. f The phase diagram revealing rotational stability of hydrogel rotor with different geometric parameters. The green dots represent that the rotors can rotate stably in situ. Pink cross symbols indicate that the rotors can rotate but not in situ. The red cross symbols indicate that the rotors cannot rotate. g Chemical Marangoni rotor benchmark. Significant metrics for comparing performance of Marangoni rotors are rotation output αmax (maximum rotation speed per unit volume) and fuel economy βmax (maximum lifetime per unit fuel). Bio-inspired hydrogel rotors in this work outperform other chemical Marangoni rotors from a diversity of materials and fuels. Yellow inverted triangles are “Gels”, green circles are “Droplets/particles”, purple triangles are “Camphor boats”, blue squares are “MOFs”. Hydrogel rotors in this work belong to the category of “Gels”. Detailed values are given in Supplementary Table 4. The scale bar is 250 µm in (a).
