Hand-over-hand Research Articles

Multimodal Sensorimotor Integration for Expert-in-the-Loop Telerobotic Surgical Training

This paper presents a novel multimodal training platform integrated with hand-over-hand (HOH) haptic guidance for dual-console surgical robotic systems such as the da Vinci Si system. The expert-in-the-loop (EIL) framework incorporates a fuzzy interface system in order to provide a trainee with adaptive authority over the procedure as well as hand-over-hand haptic guidance adjusted in real time based on the proficiency level of the trainee. The EIL expertise-oriented framework enables performance of a surgical procedure by an expert surgeon on a patient, while simultaneously providing a trainee at any stage of the motor-skills development with multimodal training without jeopardizing patient safety. Closed-loop stability of the system is investigated using the circle criterion and it is shown that the proposed architecture is unconditionally stable. Experimental evaluations are presented in support of the proposed platform through the implementation of a dual-console surgical setup consisting of the classic da Vinci surgical system (Intuitive Surgical, Inc., Sunnyvale, CA, USA) and the dV-Trainer master console (Mimic Technology, Inc., Seattle, WA, USA). To the best of our knowledge, the implemented setup is the first research platform for dual-console studies involving the classic da Vinci surgical system.

Inchworm bipedal nanowalker.

Nanowalkers take either inchworm (IW) or hand-over-hand (HOH) gait. The IW nanowalkers are advantageous over HOH ones in force generation, processivity and high-density integration, though both gaits occur in intracellular nanowalkers from biology. Artificial IW nanowalkers have been realized or proposed, but all rely on different 'head' and 'tail' to gain an adventitious direction. Here we report an inherently unidirectional IW nanowalker that is a biped with two identical legs (i.e., indistinguishable 'head' and 'tail'). This walker is made of DNA, and driven by a light-powered G-quadruplex engine. The directional inchworm motion is confirmed by operating the walker on a DNA duplex track that is designed to show a distinctive fluorescence pattern for IW walkers as compared to HOH ones. Interestingly, this walker exhibits stride-controlled IW-to-HOH gait switch and direction reversal when the track's periodic binding sites have wider and wider separation. The results altogether present an integrated mechanism for implementing nanowalkers of different gaits and directions on molecular tracks, optical potentials or even solid-state surfaces.

Biased Motion and Molecular Motor Properties of Molecular Spiders

Molecular spiders are synthetic molecular motors featuring multiple legs that each can interact with a substrate through binding and cleavage. Experimental studies suggest the motion of the spider in a matrix is biased towards uncleaved substrates, and that spider properties such as processivity can be altered by changing the binding strength of the legs to substrate [R. Pei et al., J. Amer. Chem. Soc.128, 12693 (2006)]. We investigate the origin of biased motion and molecular motor properties of bipedal spiders using Monte Carlo simulations. Our simulations combine a realistic chemical kinetic model, hand-over-hand (HOH) or inchworm (IW) modes of stepping, and the use of a 1D track. We find that substrate cleavage and spider detachment from the track are both contributing mechanisms to population bias but are not necessary for biased motion on an asymmetric track. We investigate the contributions of stepping mechanism to speed, randomness parameter, processivity, coupling and efficiency, and comment on how these molecular motor properties can be altered by changing experimentally tunable kinetic parameters. We then consider the more general case where steps can occur by any mechanism, subject to steric constraints. We compare these results with the above for bipedal spiders and then simulate quadrupedal spiders to investigate the effect of leg number on motor performance.