Light, as a special form of energy, has been recently intensively explored to power robots. However, most existing light-driven robots have limited locomotion modalities, with constrained locomotion capabilities. In this article, a bioinspired design of a light-powered soft robot is demonstrated, which can crawl on ground, squeeze its way through a small channel and jump over a barrier. The soft robot with an arch shape is made up of liquid crystal elastomer-carbon nanotube composite. When a light source with the power intensity around 1.57 Wcm -2 is scanned over the surface of the robot, it deforms and crawls forward. With the increase of the light scanning speed, the soft robot can deform to enable itself to pass through a channel, which is 25% percent lower than its body height. Subjected to light irradiation, the soft robot can also deform to a closed loop, gradually store elastic energy and suddenly release it to jump over a wall or onto a step at fast speed with the jumping distance around eight times of its body length and jumping height around five times of its body height. This article also presents mathematical models for quantitatively understanding the multimodal locomotion of the light-powered soft robot.
PurposeLaparoscopic gastrectomy is a widely accepted surgical technique. Recently, robotic gastrectomy has been developed, as an alternative minimally invasive surgical technique. This study aimed to evaluate the question of whether robotic gastrectomy is feasible and safe for the treatment of gastric cancer, due to its learning curve.Materials and MethodsWe retrospectively reviewed the prospectively collected data of 100 consecutive robotic gastrectomy patients, from November 2008 to March 2011, and compared them to 282 conventional laparoscopy patients during the same period. The robotic gastrectomy patients were divided into 20 initial cases; and all subsequent cases; and we compared the clinicopathological features, operating times, and surgical outcomes between the three groups.ResultsThe initial 20 robotic gastrectomy cases were defined as the initial group, due to the learning curve. The initial group had a longer average operating time (242.25±74.54 minutes vs. 192.56±39.56 minutes, P>0.001), and hospital stay (14.40±24.93 days vs. 8.66±5.39 days, P=0.001) than the experienced group. The length of hospital stay was no different between the experienced group, and the laproscopic gastrectomy group (8.66±5.39 days vs. 8.11±4.10 days, P=0.001). The average blood loss was significantly less for the robotic gastrectomy groups, than for the laparoscopic gastrectomy group (93.25±84.59 ml vs. 173.45±145.19 ml, P<0.001), but the complication rates were no different.ConclusionsOur study shows that robotic gastrectomy is a safe and feasible procedure, especially after the 20 initial cases, and provides a satisfactory postoperative outcome.
Specially arranged external stimuli or carefully designed geometry are often essential for realizing continuous autonomous motion of active structures without self-carried power. As a consequence, it is usually very challenging to further integrate those structures as active building blocks into a system with a complex form and multiple functions. In this letter, we report an autonomous motion of a surprisingly simple setup: a cylindrical elastomer rod on a flat hot surface or under homogeneous illumination of visible light. We further show that the rod can roll continuously without any sign of a pause after 6 h, if an obstacle is put in front of it. We demonstrate that such nonintuitive autonomous rolling results from a combination of large thermal actuation of the elastomer and heat transfer between the rod and its surroundings. Quantitative predictions of the rolling speed from the developed thermomechanics model agree reasonably well with experimental measurements. Using the autonomous rolling rods as main building blocks, we further design and fabricate a light-powered vehicle and a thermally powered conveyor for mass transport in both air and water environments.
The topological derivative-based non-iterative imaging algorithm has demonstrated its applicability in limited-aperture inverse scattering problems. However, this has been confirmed through many experimental simulation results, and the reason behind this applicability has not been satisfactorily explained. In this paper, we identify the mathematical structure and certain properties of topological derivatives for the imaging of two-dimensional crack-like thin penetrable electromagnetic inhomogeneities that are completely embedded in a homogeneous material. To this end, we establish a relationship with an infinite series of Bessel functions of integer order of the first kind. Based on the derived structure, we discover a necessary condition for applying topological derivatives in limited-aperture inverse scattering problems, and thus confirm why topological derivatives can be applied. Furthermore, we analyze the structure of multi-frequency topological derivative, and identify why this improves the single-frequency topological derivative in limited-aperture inverse scattering problems. Various numerical simulations are conducted with noisy data, and the results support the derived structure and exhibit certain properties of single- and multi-frequency topological derivatives.
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