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Bacterial contamination of implant surfaces is one of the primary causes of their failure, and this threat has been further exacerbated due to the emergence of drug‐resistant bacteria. Nanostructured mechanobactericidal surfaces that neutralize bacteria via biophysical forces instead of traditional biochemical routes have emerged as a potential remedy against this issue. Here, we report on the bactericidal activity of titania nanotubes (TNTs) prepared by anodization, a well‐established and scalable method. We investigate the differences in bacterial behavior between three different topographies and demonstrate the applicability of this technique on complex three‐dimensional (3D) geometries. It was found that the metabolic activity of bacteria on such surfaces was lower, indicative of disturbed intracellular processes. The differences in deformations of the cell wall of Gram‐negative and positive bacteria were investigated from electron micrographs Finally, nanoindentation experiments show that the nanotubular topography was durable enough against forces typically experienced in daily life and had minimal deformation under forces exerted by bacteria. Our observations highlight the potential of the anodization technique for fabricating mechanobactericidal surfaces for implants, devices, surgical instruments, and other surfaces in a healthcare setting in a cheap, scalable way. [ABSTRACT FROM AUTHOR]

In this paper, we present the design and characterization of a novel ankle robot developed at the Massachusetts Institute of Technology (MIT). This robotic module is being tested with stroke patients at Baltimore Veterans Administration Medical Center. The purpose of the on-going study is to train stroke survivors to overcome common foot drop and balance problems in order to improve their ambulatory performance. Its design follows the same guidelines of our upper extremity designs, i.e., it is a low friction, backdriveable device with intrinsically low mechanical impedance. Here, we report on the design and mechanical characteristics of the robot. We also present data to demonstrate the potential of this device as an efficient clinical measurement tool to estimate intrinsic ankle properties. Given the importance of the ankle during locomotion, an accurate estimate of ankle stiffness would be a valuable asset for locomotor rehabilitation. Our initial ankle stiffness estimates compare favorably with previously published work, indicating that our method may serve as an accurate clinical measurement tool. Index Terms--Ankle robot, foot drop, neurorehabilitation, rehabilitation robots.

We consider a simplified characterization of the postural control system that embraces two broad components: one representing the musculoskeletal dynamics in the sagittal plane and the other representing proprioceptive feedback and the central nervous system (CNS). Specifically, a planar four-segment neuromusculoskeletal model consisting of the ankle, knee, and hip degrees-of-freedom (DOFs) is described in this paper. The model includes important physiological constructs such as Hill-type muscle model active and passive muscle stiffnesses, force feedback from the Golgi tendon organ, muscle length and rate feedback from the muscle spindle, and transmission latencies in the neural pathways. A proportional-integral-derivative (PID) controller for each individual DOF is assumed to represent the CNS analog in the modeling paradigm. Our main hypothesis states that all stabilizing PID controllers for such multisegment biomechanical models can be parametrized and analytically synthesized. Our analytical and simulation results show that the proposed representation adequately shapes a postural control that (a) possesses good disturbance rejection and trajectory tracking, (b) is robust against feedback latencies and torque perturbations, and (c) is flexible to embrace changes in the musculoskeletal parameters. We additionally present detailed sensitivity analysis to show that control under conditions of limited or no proprioceptive feedback results in (a) significant reduction in the stability margins, (b) substantial decrease in the available stabilizing parameter set, and (c) oscillatory movement trajectories. Overall, these results suggest that anatomical arrangement, active muscle stiffness, force feedback, and physiological latencies play a major role in shaping motor control processes in humans. [DOI: 10.1115/1.3002763] Keywords: movement biomechanics, musculoskeletal model, dynamic stability analysis, analytic trajectory generation, neural PID controller

In this paper we address the problem of PID stabilization of a single-link inverted pendulum-based biomechanical model with force feedback, two levels of position and velocity feedback, and with delays in all the feedback loops. The novelty of the proposed model lies in its physiological relevance, whereby both small and medium latency sensory feedbacks from muscle spindle (MS), and force feedback from Golgi tendon organ (GTO) are included in the formulation. The biomechanical model also includes active and passive viscoelastic feedback from Hill-type muscle model and a second-order low-pass function for muscle activation. The central nervous system (CNS) regulation of postural movement is represented by a proportional-integral-derivative (PID) controller. Pade approximation of delay terms is employed to arrive at an overall rational transfer function of the biomechanical model. The Hermite-Biehler theorem is then used to derive stability results, leading to the existence of stabilizing PID controllers. An algorithm for selection of stabilizing feedback gains is developed using the linear matrix inequality (LMI) approach. Keywords: Single-link Biomechanical Model, Delayed Feedbacks, PID Control, Hermite-Biehler Theorem, Linear Matrix Inequality

Radiofrequency (RF) shielding is a type of electromagnetic (EM) shielding that prevents RF EM radiation from entering a building. Electrostatic fields, radio waves, and medical equipment can be insulated by multifunctional composites consisting of unique core–shell heterostructures; such materials are in high demand, given the rapid improvements in medical electronics and their expanding clinical applications, which represent a serious challenge of EM pollution in clinical settings. In order to avoid malfunction, the electronics in critical care devices in hospitals must be shielded from radiation. In order to create a material that can block radio waves while still utilizing RF to disinfect the surface, we built core–shell nanostructures to encase critical medical electronics. In this work, we discuss a polymer composite that is customized to provide EM shielding while also safeguarding critical care bioelectronics. Its bactericidal function, on the other hand, prevents nosocomial dangerous microorganisms from spreading contamination. We developed a library of Fe3O4@Ag and Ag@Fe3O4 core–shell and binary heterostructures with configurable Ag or Fe3O4 shell thicknesses. These heterostructures were subsequently combined with ethylene–vinyl acetate (EVA), a thermoplastic polymer, to create flexible composites that may attenuate incident EM radiation. The protective viability (SE) of Fe3O4@Ag core–shell and Ag@Fe3O4 binary nanoparticles in EVA was −32.1 and −20 dB, respectively. Due to localized heating, the Fe3O4@Ag- and Ag@Fe3O4-based nanocomposites exhibited "self-cleaning" behavior, displaying antibacterial activity in the vicinity of a 2.4 GHz wireless fidelity source against Pseudomonas aeruginosa. Taken together, these multifunctional, adaptable composites can protect electronic gadgets from EM radiation and harness RF to render the surface antibacterial, an important attribute in clinical settings. [ABSTRACT FROM AUTHOR]

Abstract Background Hemiparesis after stroke often leads to impaired ankle motor control that impacts gait function. In recent studies, robotic devices have been developed to address this impairment. While capable of imparting forces to assist during training and gait, these devices add mass to the paretic leg which might encumber patients' gait pattern. The purpose of this study was to assess the effects of the added mass of one of these robots, the MIT's Anklebot, while unpowered, on gait of chronic stroke survivors during overground and treadmill walking. Methods Nine chronic stroke survivors walked overground and on a treadmill with and without the anklebot mounted on the paretic leg. Gait parameters, interlimb symmetry, and joint kinematics were collected for the four conditions. Repeated-measures analysis of variance (ANOVA) tests were conducted to examine for possible differences across four conditions for the paretic and nonparetic leg. Results The added inertia and friction of the unpowered anklebot had no statistically significant effect on spatio-temporal parameters of gait, including paretic and nonparetic step time and stance percentage, in both overground and treadmill conditions. Noteworthy, interlimb symmetry as characterized by relative stance duration was greater on the treadmill than overground regardless of loading conditions. The presence of the unpowered robot loading reduced the nonparetic knee peak flexion on the treadmill and paretic peak dorsiflexion overground (p < 0.05). Conclusions Our results suggest that for these subjects the added inertia and friction of this backdriveable robot did not significantly alter their gait pattern.