Conforming Capacitive Load Cells for Conical Pick Cutters.

In underground coal mining, machine operators put themselves at risk when getting close to the machine or cutting face to observe the process. To improve the safety and efficiency of machine operators, a cutting force sensor is proposed. A linear cutting machine is used to cut two separate coal samples cast in concrete with conical pick cutters to simulate mining with a continuous miner. Linear and neural network regression models are fit using 100 random 70:30 test/train splits. The normal force exceeds 60 kN during the rock-cutting tests, and it is averaged using a low pass filter with a 10 Hertz cutoff frequency. The sensor uses measurements of the resonant frequency of capacitive cells in a steel case to determine cutting forces. When used in the rock-cutting experiments, the sensor conforms to the tooling and the stiffness and sensitivity are increased compared to the initial configuration. The sensor is able to track the normal force on the conical picks with a mean absolute error less than 6 kN and an R2 score greater than 0.60 using linear regression. A small neural network with a second-order polynomial expansion is able to improve this to a mean absolute error of less than 4 kN and an R2 score of around 0.80. Filtering measurements before regression fitting is explored. This type of sensor could allow operators to assess tool wear and material type using objective force measurements while maintaining a greater distance from the cutting interface.

Age-specific biomechanical challenges and engagement in dynamic balance training with robotic or virtual real-time visual feedback.

Challenging balance training that targets age-related neuromuscular and motor coordination deficits is needed for effective fall prevention therapy. Goal-directed training can provide intrinsically motivating balance activities but may not equally challenge balance for all age groups. Therefore, the purpose of this research was to quantify age-specific effects of dynamic balance training with real-time visual feedback. Kinematics, muscle activity, and user perceptions were collected for forty healthy adults (20 younger, 18-39 years; 20 older, 58-74 years), who performed a single balance training session with or without real-time visual feedback. Feedback involved controlling either a physical mobile robot or screen-based virtual ball through a course with standing tilt motions from an instrumented wobble board. Dynamic balance training was more challenging for older compared to younger adults, as measured by significantly higher dorsiflexor and knee extensor muscle activity and ankle co-contractions (50%-80%, p<0.05). Older participants also performed more motion while training without feedback compared to younger adults (22%-65%, p<0.05). Robotic and virtual real-time visual feedback elicited similar biomechanical adaptations in older adults, reducing motions to similar levels as younger adults and increasing ankle co-contractions (p<0.05). Despite higher muscular demand, perceived physical exertion and high enjoyment levels (Intrinsic Motivation Inventory >0.80) were consistent across groups. However, robotic visual feedback may be more challenging than virtual feedback based on more frequent balance corrections, lower perceived competence, and lower game scores for older compared to younger adults. These findings collectively support the feedback system's potential to provide engaging and challenging at-home balance training across the lifespan.

Coupling magnetic torque and force for colloidal microbot assembly and manipulation.

For targeted transport in the body, biomedical microbots (µbots) must move effectively in three-dimensional (3D) microenvironments. Swimming µbots translate via asymmetric or screw-like motions while rolling ones use friction with available surfaces to generate propulsive forces. We have previously shown that planar rotating magnetic fields assemble µm-scale superparamagnetic beads into circular µbots that roll along surfaces. In this, gravity is required to pull µbots near the surface; however, this is not necessarily practical in complex geometries. Here we show that rotating magnetic fields, in tandem with directional magnetic gradient forces, can be used to roll µbots on surfaces regardless of orientation. Simplifying implementation, we use a spinning permanent magnet to generate differing ratios of rotating and gradient fields, optimizing control for different environments. This use of a single magnetic actuator sidesteps the need for complex electromagnet or tandem field setups, removes requisite gravitational load forces, and enables µbot targeting in complex 3D biomimetic microenvironments.

Balance Therapy With Hands-Free Mobile Robotic Feedback for At-Home Training Across the Lifespan.

Providing aging adults with engaging, at-home balance therapy is essential to promote long-term adherence to unsupervised training and to foster independence. We developed a portable interactive balance training system that provides real-world visual cues on balance performance using wobble board tilt angles to control the speed of a robotic car platform in a three-dimensional environment. The goal of this study was to validate this mobile balance therapy system for home use across the lifespan. Twenty younger (18-39 years) and nineteen older (58-74 years) healthy adults performed balance training with and without visual feedback while standing on a wobble board instrumented with a consumer-grade inertial measurement unit (IMU) and optical motion tracking markers. Participants performed feedback trials based on either the robotic car's movements or a commercially-available virtual game. Wobble board tilt measurements were highly correlated between IMU and optical measurement systems ( [Formula: see text]), with high agreement in outcome metrics ( [Formula: see text]) and small bias ( [Formula: see text]). Both measurement systems identified similar aging, feedback, and stance type effects including (1) altered movement control when older adults performed tilting trials with either robotic or virtual feedback compared to without feedback, (2) two-fold greater wobble board oscillations in older vs. younger adults during steady standing, (3) no difference in board oscillations during steady standing in narrow vs. wide double support, and (4) greater wobble board oscillations for single compared to double support. These findings demonstrate the feasibility of implementing goal-directed robotic balance training with mobile tracking of balance performance in home environments.

Magnetic Control of a Flexible Needle in Neurosurgery.

Minimally invasive neurosurgery does not require large incisions and openings in the skull to access the desired brain region, which often results in a faster recovery with fewer complications than traditional open neurosurgery. For disorders treated by the implantation of neurostimulators and thermocoagulation probes, current procedures incorporate a straight rigid needle, which restricts surgical trajectories and limits the number of possible targets and degrees of freedom at the respective target. A steerable needle with a flexible body could overcome these limitations. In this paper, we present a flexible needle steering system with magnetic and fluoroscopic guidance for neurosurgical procedures. A permanent magnet at the proximal end of a flexible needle is steered by an external magnetic field, and the resultant tip-deflection angle bends the flexible body like a bevel-tip needle. We implemented a kinematic model for the magnetic needle derived from a nonholonomic bicycle model and a closed-loop control strategy with feed-forward and feed-back components using a chained-form transformation. The proposed needle steering method was investigated through in vitro and ex vivo experiments.

iRebot: An Interactive Rehabilitation Robot with Gesture Control.

Physical therapy efficacy relies on patient compliance and motivation. However, the monotony, intensity, and expense of most therapy routines do not promote engagement. Technology-based rehabilitation has the potential to provide engaging and cost-effective treatment, leading to better compliance and mobility outcomes. We present an interactive rehabilitation robot (iRebot) as an affordable, gesture-controlled vehicle that can provide a form of entertainment while conducting physical therapy. Healthy participants (n=11) executed a test maze with the iRebot for six repeated trials, three with each hand. Survey scores and quantitative metrics were evaluated to assess system usability and baseline motor performance, respectively. Wrist mobility across participants was evaluated, with an active range of motion of 39.7± 13° and 72.8± 18° for pitch and roll, respectively. In the course of conducting a single trial (time duration=87.2±67 sec), the participants performed on average 30 full wris t motion repetitions (e.g., flexion/extension). Participants rated the system's usability as excellent (survey score: 85 ± 13), and all participants indicated they would prefer iRebot over standard therapy. The iRebot demonstrated potential as an evidence-based rehabilitation tool based on excellent user ratings and the ability to monitor at- home compliance and motor performance.

A Gesture-Controlled Rehabilitation Robot to Improve Engagement and Quantify Movement Performance.

Rehabilitation requires repetitive and coordinated movements for effective treatment, which are contingent on patient compliance and motivation. However, the monotony, intensity, and expense of most therapy routines do not promote engagement. Gesture-controlled rehabilitation has the potential to quantify performance and provide engaging, cost-effective treatment, leading to better compliance and mobility. We present the design and testing of a gesture-controlled rehabilitation robot (GC-Rebot) to assess its potential for monitoring user performance and providing entertainment while conducting physical therapy. Healthy participants (n = 11) completed a maze with GC-Rebot for six trials. User performance was evaluated through quantitative metrics of movement quality and quantity, and participants rated the system usability with a validated survey. For participants with self-reported video-game experience (n = 10), wrist active range of motion across trials (mean ± standard deviation) was 41.6 ± 13° and 76.8 ± 16° for pitch and roll, respectively. In the course of conducting a single trial with a time duration of 68.3 ± 19 s, these participants performed 27 ± 8 full wrist motion repetitions (i.e., flexion/extension), with a dose-rate of 24.2 ± 5 reps/min. These participants also rated system usability as excellent (score: 86.3 ± 12). Gesture-controlled therapy using the GC-Rebot demonstrated the potential to be an evidence-based rehabilitation tool based on excellent user ratings and the ability to monitor at-home compliance and performance.

Magnetically Steered Robotic Insertion of Cochlear-Implant Electrode Arrays: System Integration and First-In-Cadaver Results.

Cochlear-implant electrode arrays (EAs) must be inserted accurately and precisely to avoid damaging the delicate anatomical structures of the inner ear. It has previously been shown on the benchtop that using magnetic fields to steer magnet-tipped EAs during insertion reduces insertion forces, which correlate with insertion errors and damage to internal cochlear structures. This paper presents several advancements toward the goal of deploying magnetic steering of cochlear-implant EAs in the operating room. In particular, we integrate image guidance with patient-specific insertion vectors, we incorporate a new nonmagnetic insertion tool, and we use an electromagnetic source, which provides programmable control over the generated field. The electromagnet is safer than prior permanent-magnet approaches in two ways: it eliminates motion of the field source relative to the patient's head and creates a field-free source in the power-off state. Using this system, we demonstrate system feasibility by magnetically steering EAs into a cadaver cochlea for the first time. We show that magnetic steering decreases average insertion forces, in comparison to manual insertions and to image-guided robotic insertions alone.

Catalytic Locomotion of Core-Shell Nanowire Motors.

We report Au/Ru core-shell nanowire motors. These nanowires are fabricated using our previously developed electrodeposition-based technique, and their catalytic locomotion in the presence of H2O2 is investigated. Unlike conventional bimetallic nanowires that are self-electroosmotically propelled, our open-ended Au/Ru core-shell nanowires show both a noticeable decrease in rotational diffusivity and increase in motor speed with increasing nanowire length. Numerical modeling based on self-electroosmosis attributes decreases in rotational diffusivity to the formation of toroidal vortices at the nanowire tail, but fails to explain the speed increase with length. To reconcile this inconsistency, we propose a combined mechanism of self-diffusiophoresis and electroosmosis based on the oxygen gradient produced by catalytic shells. This mechanism successfully explains not only the speed increase of Au/Ru core-shell nanomotors with increasing length, but also the large variation in speed among Au/Ru, Au/Rh, and Rh/Au core-shell nanomotors. The possible contribution of diffusiophoresis to an otherwise well-established electroosmotic mechanism sheds light on future designs of nanomotors, at the same time highlighting the complex nature of nanoscale propulsion.

Soft micromachines with programmable motility and morphology.

Nature provides a wide range of inspiration for building mobile micromachines that can navigate through confined heterogenous environments and perform minimally invasive environmental and biomedical operations. For example, microstructures fabricated in the form of bacterial or eukaryotic flagella can act as artificial microswimmers. Due to limitations in their design and material properties, these simple micromachines lack multifunctionality, effective addressability and manoeuvrability in complex environments. Here we develop an origami-inspired rapid prototyping process for building self-folding, magnetically powered micromachines with complex body plans, reconfigurable shape and controllable motility. Selective reprogramming of the mechanical design and magnetic anisotropy of body parts dynamically modulates the swimming characteristics of the micromachines. We find that tail and body morphologies together determine swimming efficiency and, unlike for rigid swimmers, the choice of magnetic field can subtly change the motility of soft microswimmers.

Perforation forces of the intact porcine anterior lens capsule.

During the first step of cataract surgery, the lens capsule is perforated and a circular hole is created with a sharp instrument, a procedure called capsulorhexis. To develop automated systems that can assist ophthalmologists during capsulorhexis, the forces required must be quantified. This study investigates perforation forces of the central anterior lens capsule in porcine eyes, which are used as a conservative model for the human eye. A micro-mechanical characterisation method is presented that measures capsular bag perforation forces with a high precision positioning and high-resolution force sensing system. The force during perforation of the anterior lens capsule was measured with various sized needles and indentation speeds and is found to be 15-35mN. A bio-mechanical model is identified that describes an exponential correlation between indentation force and depth, indicating strain hardening behaviour of the porcine anterior lens capsule.

Self-folding hydrogel bilayer for enhanced drug loading, encapsulation, and transport.

Hydrogel-based robotic microdevices are currently investigated for minimally invasive medical procedures. Hydrogels are especially suited to targeted drug delivery applications as they are able to carry several times more drug solution than its dry weight. A major drawback of these system is that drug release takes place before reaching the targeted area in the body. We introduce a strategy based on a self-folding bilayer to prevent release during transportation without hindering the drug loading efficiency of the hydrogel. The drug is loaded into the hydrogel matrix at room temperature. When the temperature is increased to body temperature, the hydrogel-matrix collapses and the self-folded bilayer refolds into another tube. In this configuration, we observed a significant reduction in drug leakage with less than 5% drug loss during encapsulation. Finally, we demonstrate that the tube can be manipulated magnetically, which shows its potential use in targeted drug delivery applications.

3D Printed Microtransporters: Compound Micromachines for Spatiotemporally Controlled Delivery of Therapeutic Agents.

Functional compound micromachines are fabricated by a design methodology using 3D direct laser writing and selective physical vapor deposition of magnetic materials. Microtransporters with a wirelessly controlled Archimedes screw pumping mechanism are engineered. Spatiotemporally controlled collection, transport, and delivery of micro particles, as well as magnetic nanohelices inside microfluidic channels are demonstrated.