A training system for virtual surgical incisions with haptic playback

The haptic playback system is important to the training of sensorimotor skills. With the intent for training medical students in surgery, a real-time incision training system with haptic playback is developed in this paper. This system has three modes. Mode I sets the standard cutting trajectory of the incision operation carried out by an expert. Mode II allows students to track the trajectory by haptic guidance to feel the expert's motion. Mode III lets students experience the force feeling of the expert by following the trajectory via the visual cue. To accomplish these tasks, an adjustment proportional-derivative (PD) controller and a cutting model with real-time haptic feedback are devised. The cutting model adopts the mesh adaption method for real-time simulations of progressive cutting operations. These devised methods have been configured with a haptic device PHANToM Desktop to validate the capability of the proposed training system.     

State-of-the-Art in Force and Tactile Sensing for Minimally Invasive Surgery

Haptic perception plays a very important role in surgery. It enables the surgeon to feel organic tissue hardness, measure tissue properties, evaluate anatomical structures, and allows him/her to commit appropriate force control actions for safe tissue manipulation. However, in minimally invasive surgery, the surgeon's ability of perceiving valuable haptic information through surgical instruments is severely impaired. Performing the surgery without such sensory information could lead to increase of tissue trauma and vital organic tissue damage. In order to restore the surgeon's perceptual capability, methods of force and tactile sensing have been applied with attempts to develop instruments that can be used to detect tissue contact forces and generate haptic feedback to the surgeon. This paper reviews the state-of-the-art in force and tactile sensing technologies applied in minimally invasive surgery. Several sensing strategies including displacement-based, current-based, pressure-based, resistive-based, capacitive-based, piezoelectric-based, vibration-based, and optical-based sensing are discussed.     

Analysis of Finger Motion Coordination during Packaging Interactions

Packaging accessibility is a significant problem for many older people. Whilst the majority of studies have focused on issues surrounding strength, work has shown that dexterity required to open a pack is also a major issue for many older people. Hence, the work undertaken here reports a quantitative study that aimed to analyse motion coordination patterns across digits 2–5 (index to little finger) during interactions with three of the most common types of packaging: plastic bottles, jars and crisps packets, and comparing those interactions with a common measure of dexterity, the Perdue Pegboard. Ten subjects (six male participants and four female participants) were examined whilst reaching forward to grasp and open a 300 ml plastic bottle and a 500 g jar. A 10‐camera optoelectronic motion capture system measured trajectories of 25 miniature reflective markers placed on the dorsal surface landmarks of the hand. Joint angular profiles for 12 involved flexion–extension movements were derived from the measured coordinates of surface markers. The results showed that finger correlations vary widely across the differing pack formats with the crisps having the lowest finger movement correlation and the jar having the highest. Speed and jerk metrics were also seen to vary across the various pack formats. However, finger correlations were seen to be more relevant to perceive dexterity of pack opening than finger speeds and jerk motions. Copyright © 2017 John Wiley & Sons, Ltd.     

Multimode Hydraulically Amplified Electrostatic Actuators for Wearable Haptics

The sense of touch is underused in today’s virtual reality systems due to lack of wearable, soft, mm-scale transducers to generate dynamic mechanical stimulus on the skin. Extremely thin actuators combining both high force and large displacement are a long-standing challenge in soft actuators. Sub-mm thick flexible hydraulically amplified electrostatic actuators are reported here, capable of both out-of-plane and in-plane motion, providing normal and shear forces to the user’s fingertip, hand, or arm. Each actuator consists of a fluid-filled cavity whose shell is made of a metalized polyester boundary and a central elastomer region. When a voltage is applied to the annular electrodes, the fluid is rapidly forced into the stretchable region, forming a raised bump. A 6 mm × 6 mm × 0.8 mm actuator weighs 90 mg, and generates forces of over 300 mN, out-of-plane displacements of 500 µm (over 60% strain), and lateral motion of 760 µm. Response time is below 5 ms, for a specific power of 100 W kg⁻¹. In user tests, human subjects distinguished normal and different 2-axis shear forces with over 80% accuracy. A flexible 5 × 5 array is demonstrated, integrated in a haptic sleeve.     

A heuristic to capture multi-directional lateral tactile perception

Multi-directional tactile perception adds significant complexity when interpreting haptic experimental data. In perceiving tactile stimulus direction, we often observe a lack of one-to-one stimulus-response compatibility, mostly due to confounding sensations that reinforce and/or distort a primary stimulus. This study presents the development of a metric to capture multi-directional lateral tactile perception on a finger pad. Sixty-two subjects rated the direction and magnitude of lateral motion from a single probe moving in one of the eight possible directions. A heuristic based on a vector matrix was developed to capture and integrate the relative contribution of each subject's rated directional perception in x–y coordinates. This article explains the theoretical underpinnings and the justifications for this heuristic and highlights the usefulness of this approach for future haptic system designs.     

Haptic modeling for a virtual coordinate measuring machine

Introducing a haptic device into coordinate measuring machine (CMM) inspection path planning leads to the proposal of a novel CMM off-line inspection path planning environment, a haptic virtual coordinate measuring machine (HVCMM), which makes use of the haptic modeling technique for CMM off-line programming. The HVCMM is an accurate model of a real CMM, which simulates a CMM's operation and its measurement process in a virtual environment with haptic perception. In this paper, a simple and effective mechanics model is implemented for the proposed HVCMM. The HVCMM enables CMM off-line programming to take place exactly as if an operator were in front of a real CMM and moving a real CMM probe. Even more, operators can feel the collision between the CMM and a part. Since there is a force feedback when the probe reaches the surface of the part, besides showing the contact in the HVCMM environment, it is much easier to generate a collision-free probe path than using other off-line inspection planning methods. The HVCMM not only facilitates inspection path planning, but also speeds it up because the operator does not need to slow the probe down when it is approaching an object. Combined visual and force feedback is the best indicator for selecting measurement points.     

Exploring the interatomic forces between tip and single molecules during STM manipulation

The interaction between a single molecule and the STM tip during intramolecular manipulation is investigated in detail. We show that the conformational change of complex organic molecules can be induced reversibly and very reliably by using exclusively attractive forces. By studying the dependence of this process on the bias voltage and the tip position, the driving forces are characterized. Different regimes of tip-molecule interactions are observed as a function of the distance.     

超支化预聚物的合成及对聚合物分散液晶膜电光性能的影响

聚合物基体对聚合物分散液晶(PDLC)膜电光性能影响很大。文中,用不同比例单乙烯基和二乙烯基单体通过可逆加成-断裂链转移自由基聚合(RAFT)得到了一系列超支化聚合物。这些超支化聚合物可作为"活性"预聚物用于聚合诱导相分离(PIPS)来制备超支化树脂基PDLC膜。结果表明,添加不同预聚物导致不同的表面形貌,进而影响到阈值电压大小。驱动电压对聚合物基体分子量有一定的依赖性,分子量高的基体驱动电压相对较高。此外,滞后和记忆效应随基体支化度提高而减小,这可能与超支化结构增强了聚合物与液晶间的相互作用力有关。     

Numerical integration of non-linear elastic multi-body systems

This paper is concerned with the modelling of nonlinear elastic multi-body systems discretized using the finite element method. The formulation uses Cartesian co-ordinates to represent the position of each elastic body with respect to a single inertial frame. The kinematic constraints among the various bodies of the system are enforced via the Lagrange multiplier technique. The resulting equations of motion are stiff, non-linear, differential-algebraic equations. The integration of these equations presents a real challenge as most available techniques are either numerically unstable, or present undesirable high frequency oscillations of a purely numerical origin. An approach is proposed in which the equations of motion are discretized so that they imply conservation of the total energy for the elastic components of the system, whereas the forces of constraint are discretized so that the work they perform vanishes exactly. The combination of these two features of the discretization guarantees the stability of the numerical integration process for non-linear elastic multi-body systems. Examples of the procedure are presented.     

Numerical simulation of transport and placement of multi-sized proppants in a hydraulic fracture in vertical wells

The placement of proppant in hydraulic fractures, which is governed by slurry flow, proppant transport and settlement, can significantly affect the conductivity of the fracture, and this will subsequently affect the productivity of the hydraulically fractured wells. To investigate proppant transport mechanisms and placement profiles in a hydraulic fracture, computational fluid dynamics coupled with discrete element method is used to model slurry flow and micro-mechanical interactions of proppant particles in a fracture. The effect of the solid phase is introduced in terms of volumetric porosity and particle interaction forces, and a contact model is used to simulate the particle-to-particle and the particle-to-wall interactions. The particles are modelled as real spheres, and for a two-dimensional computational model, an out-of-plane length of the maximum particle diameter is assumed. The proppants are injected into the fracture through seven perforations to mimic the slurry flow in a fracture in vertical wells. When the proppants are injected into a fracture driven by thin fracturing fluids, they quickly settle out of the fluid and accumulate on the fracture bottom, forming a proppant dune. A three-layer flow pattern forms in the fracture consisting of: (1) a stationary proppant bed at the bottom, (2) a proppant-fluid mixture layer above it, and (3) a clean fluid layer at the top. During the early stages, the motion of the proppants is governed by suspension, settlement and fluidization, and the injected proppants mainly settle and accumulate near the wellbore. When the equilibrium height of the dune is reached, the dune changes to a proppant bank. Then the later injected proppants are transported to overshoot the bank and dragged deeper into the fracture. A new proppant transport mechanism, vortex, is observed, which governs the proppant motion after they leave the proppant bank.     

Intermolecular Chemistry in Solid Polymer Electrolytes for High‐Energy‐Density Lithium Batteries

Solid polymer electrolytes (SPEs) have aroused wide interest in lithium batteries because of their sufficient mechanical properties, superior safety performances, and excellent processability. However, ionic conductivity and high‐voltage compatibility of SPEs are still yet to meet the requirement of future energy‐storage systems, representing significant barriers to progress. In this regard, intermolecular interactions in SPEs have attracted attention, and they can significantly impact on the Li⁺ motion and frontier orbital energy level of SPEs. Recent advances in improving electrochemcial performance of SPEs are reviewed, and the underlying mechanism of these proposed strategies related to intermolecular interaction is discussed, including ion–dipole, hydrogen bonds, π–π stacking, and Lewis acid–base interactions. It is hoped that this review can inspire a deeper consideration on this critical issue, which can pave new pathway to improve ionic conductivity and high‐voltage performance of SPEs.     

Real-time template-assisted manipulation of nanoparticles in a multilayer nanofluidic chip

The ability to control dynamically the flow and placement of nanoscale particles and biomolecules in a biocompatible, aqueous environment will have profound impact in advancing the fields of nanoplasmonics, nanophotonics, and medicine. Here, an approach based on electrokinetic forces is demonstrated that enables dynamically controlled placement of nanoparticles into a predefined pattern. The technique uses an applied voltage to manipulate nanoparticles in a multilayer nanofluidic chip architecture. Simulations of the nanoparticles' motion in the nanofluidic chip validate the approach and are confirmed by experimental demonstration to produce uniform 200-nm-diameter spherical nanoparticle arrays. The results are important as they provide a new method that is capable of dynamically capturing and releasing nanoscale particles and biomolecules in an aqueous environment, which could lead to the creation of reconfigurable nanostructure patterns for nanoplasmonic, nanophotonic, biological sensing, and drug-delivery applications.     

Speed choice and driving performance in simulated foggy conditions

Driving in fog is a potentially dangerous activity that has been investigated in a number of different ways; however, most have focused on identifying the underlying perceptual changes that result in an inability to perceive speed of vehicle motion. Although the previous research has identified the perceptual changes associated with driving in fog and shows that people are highly likely to perceive their speed to be higher than it actually is, these research studies have not investigated driving behavior when drivers are allowed to maintain speed as they feel appropriate and make use of the vehicle's speedometer. In addition, much of the existing research focuses on speed perception and presents a limited view of other driving performance metrics in terms of lane keeping and event detection. The current study addresses these issues utilizing a driving simulator-based method where fog is simulated as a distance dependent contrast reduction while having participants drive at speeds they feel are appropriate. A number of different instructions and speed feedback mechanisms were tested in order to determine how drivers react when driving in varying levels of fog. Results also include lane keeping measures in order to assess whether drivers are willing to drive at speeds where their lane keeping performance is degraded due to the reduced visibility. Results indicate that, in general, drivers do not tend to slow down significantly until visibility distance is drastically reduced by fog; however, lane keeping ability is maintained throughout most of the range of visibility distances. Lane keeping ability was reduced only when fog results in visibility distances <30 m. Overall, the current study shows that drivers are willing and able to maintain vehicular control at high speed when driving in fog; however, it is important to note that drivers chose to drive at speeds where they would be incapable of stopping to avoid obstacles in the roadway even if they were to identify and react to the obstacle immediately at the border of visibility distance. This research suggests that safety benefits may be gained by convincing drivers to slow down more than they would on their own when driving in fog or enhancing a vehicle's ability to identify and react to hazards that are not visible to the driver. In order to further understand the effects of driving in fog, future naturalistic driving research should focus on identifying and mitigating risky behaviors associated with driving in foggy conditions.     

The Effect of Jar Holding Posture on Finger Force and Torque during a Jar‐Opening Task for Young Females

Many young females have difficulty opening jars. Although previous studies have attempted to clarify the body posture effect during such a task, the experiments therein focused on a single digit or actions with unnatural finger positions and were further restricted to upper extremity postures. A further study is required to investigate the fingers’ coordination, as well as each subject's natural and self‐selected upper extremity posture and finger grasp location when opening a jar. This study focused on the forces and coordination of the right hand fingers during a jar opening movement under both vertical and free‐way opening postures. A jar simulator was set up to record the forces applied by finger groups (the thumb, the index–middle finger group, and the ring–little finger group) of the right hand. A self‐selected finger position and free‐arm posture of each subject were allowed. Results show that the force vectors of the finger groups were all in the counterclockwise direction for both postures. The total force and overall torque of the right hand decreased in the vertical opening posture. The thumb produced greater tangential and resultant forces in the vertical opening posture. Despite normal forces being 1.82–3.54 times the tangential forces for both postures, no difference was found for the normal force to tangential force ratio for each finger group between the two opening postures. The index–middle finger group had similar torque contributions for both postures. The torque contribution of the thumb increased (26% and 21% for vertical and free‐way posture, respectively), while the ring–little finger group torque contribution decreased (35% and 42% for vertical and free‐way posture, respectively) in the vertical opening posture. As such, the free‐way opening posture is the better strategy for young females to open a jar. Copyright © 2013 John Wiley & Sons, Ltd.     

Effective manipulation for a multi-DOF robot manipulator in laboratory environments

Robots are expected to enter human environments soon, and many challenging problems may then emerge when facing uncertain and varying environments. Among the challenges, one issue of great interest is how they can be effectively operated for task execution. If a robot is not to be controlled by detailed analysis and program coding, one appealing alternative is to provide a kind of manipulation system which enables the user to operate the robot naturally and efficiently. This idea has motivated us to develop an effective manipulation system for multi-degree of freedom (DOF) robot manipulators based on a 6-DOF haptic device. In this article, we focus on the laboratory environment, which is somewhat organized, but still demands sophisticated human manipulation. The proposed manipulation system, aimed for 3-D applications, provides two kinds of assistance. One is to enhance the linkage between the user and robot manipulator via the haptic clue. The other is to guide the movement of the user during task execution via a set of virtual tools, e.g., a ruler. We also propose a method for achieving smooth force rendering in manipulation, especially during the transition between two consecutive manipulations for guidance. For performance evaluation, this system is employed to conduct experiments in the chemical laboratory, which involve delicate and challenging maneuvers.     

基于多腔软体驱动器的柔性手指设计

针对现有软体柔性手指运动自由度少的问题，设计了一款基于气动多腔软体驱动器的柔性手指。基于软体动物的运动特征，对多腔软体驱动器的结构进行了设计；根据虚功原理，建立了软体驱动器的力学模型和柔性手指的位姿方程；利用Abaqus CAE有限元仿真软件对柔性手指进行了力学仿真，得到了柔性手指偏转角度与输入气压的关系曲线；以单向转动软体驱动器为研究对象，通过输入特定气压值来分析其偏转角度与输入气压的关系，并对比了偏转角度—输入气压关系曲线的理论计算、仿真分析和试验结果的差异。试验结果显示，在偏转角度为0°~80°时，单向转动软体驱动器理论计算、仿真分析与实际测得的偏转角度—输入气压曲线的变化趋势基本一致。研究表明，所建立的单向转动软体驱动器力学模型能够较为准确地描述驱动器偏转角度的变化，所建立的手指位姿方程能够根据各关节的偏转角度求得手指各个节点的空间坐标,为手指的运动控制提供了基础。     

Nonlinear and nonplanar dynamics of suspended nanotube and nanowire resonators

Previous works on suspended carbon nanotube and nanowire resonators assume a priori that they oscillate in a single plane. We explore the nonlinear dynamics of such resonators and demonstrate that they can suddenly transition from a planar motion to a whirling, "jump rope" like motion. We identify nondimensional gate voltage, resonator geometry, quality factor, and flexural and axial elastic stiffnesses for which such motions can arise. The deliberate use of nonlinear and nonplanar motions opens up a variety of new modalities for this class of nanoelectromechanical systems that are not accessible in the linear operating regime.     

Lessons from experienced guideline implementers: attend to many factors and use multiple strategies

BACKGROUND: Studies of clinical guideline implementation have focused almost entirely on changing individual clinician behavior with single intervention strategies and without much attention to the situational context. The goal of this project was to learn from clinic leaders, seasoned in the guideline implementation process, what contextual variables they viewed as important and whether implementation success could be expected if only a single implementation strategy was used. METHODS: In 1998, 12 people with extensive experience in leading clinical guideline implementation were identified who were thought to have particularly keen insight into the process. They were interviewed to generate variables they considered important, as well as strategies they considered effective when used appropriately. A modified nominal group/Delphi process was then used for rating these variables and strategies, and the reactions of international experts were obtained to add perspective to this information. RESULTS: Eighty-seven variables and 25 strategies were identified, clustering in 6 categories (ranked in order of importance by the panel): organizational capabilities for change, infrastructure for implementation, implementation strategies, medical group characteristics, guideline characteristics, and external environment. All six categories were considered to be important, key, or essential by the experienced implementers, although variables within a medical group that directly affect its ability to undertake planned change were rated as much more important than either guideline characteristics or the external environment. DISCUSSION: Although the opinions of those experienced in the process of guideline implementation are primarily of value for generating hypotheses, panel members believe that implementation efforts focusing on the individual physician with a single strategy are unlikely to be successful. Rather, implementation efforts must use multiple strategies that take account of multiple characteristics of the guideline, practice organization, and external environment.     

Mesoscopic fabric models using a discrete mass-spring approach: Yarn-yarn interactions analysis

A meso/macro discrete model of fabric has been developed, accounting for yarn-yarn interactions occurring at the crossing points. The fabric yarns, described initially by a Fourier series development, are discretized into elastic straight bars represented by stretching springs and connected at frictionless hinges by rotational springs. The motion of each node is described by a lateral displacement and a rotation. The compressibility of both yarns is expressed as a kinematic relationship, considering frictionless motions of the yarns. The expression of the reaction force exerted by the transverse yarns at the contact points is then assessed, from which the work of the reaction forces is established. The equilibrium shape of the yarn is obtained as the minimum of its total potential energy, accounting for the work of the reaction forces due to the transverse yarns. Simulations of a traction curve of a single yarn are performed, that evidence the effect of the yarn interactions and the main deformation mechanisms.     

The influence of crystal habit on the prediction of dry powder inhalation formulation performance using the cohesive-adhesive force balance approach

The aim of this investigation was to study the influence of crystalline habit of active pharmaceutical ingredients on the cohesive-adhesive force balance within model dry powder inhaler (DPI) formulations and the corresponding affect on DPI formulation performance. The cohesive-adhesive balance (CAB) approach to colloid probe atomic force microscopy (AFM) was employed to determine the cohesive and adhesive interactions of micronized budesonide particles against the {102} and {002} faces of budesonide single crystals and crystalline substrates of different sugars (cyclodextrin, lactose, trehalose, raffinose, and xylitol), respectively. These data were used to measure the relative level of cohesion and adhesion via CAB and the possible influence on in vitro performance of a carrier-based DPI formulation. Varying the crystal habit of the drug had a significant effect on the cohesive measurement of micronized budesonide probes, with the cohesive values on the {102} faces being approximately twice that on the {002} crystal faces. However, although different CAB values were measured with the sugars with respect to the crystal faces chosen for the cohesive-based measurement, the overall influence on the rank order of the CAB values was not directly influenced. For these data sets, the CAB gradient indicated that a decrease in the dominance of the adhesive forces led to a concomitant increase in fine particle delivery, reaching a plateau as the cohesive forces became dominant. The study suggested that crystal habit of the primary drug crystals influences the cohesive interactions and the resulting force balance measurements of colloid probe CAB analysis.