Carbon Black/PDMS Based Flexible Capacitive Tactile Sensor for Multi-Directional Force Sensing

Flexible sensing tends to be widely exploited in the process of human–computer interactions of intelligent robots for its contact compliance and environmental adaptability. A novel flexible capacitive tactile sensor was proposed for multi-directional force sensing, which is based on carbon black/polydimethylsiloxane (PDMS) composite dielectric layer and upper and lower electrodes of carbon nanotubes/polydimethylsiloxane (CNTs/PDMS) composite layer. By changing the ratio of carbon black, the dielectric constant of carbon black/PDMS composite layer increases at 4 wt%, and then decreases, which was explained according to the percolation theory of the conductive particles in the polymer matrix. Mathematical model of force and capacitance variance was established, which can be used to predict the value of the applied force. Then, the prototype with carbon black/PDMS composite dielectric layer was fabricated and characterized. SEM observation was conducted and a ratio was introduced in the composites material design. It was concluded that the dielectric constant of carbon sensor can reach 0.1 N within 50 N in normal direction and 0.2 N in 0–10 N in tangential direction with good stability. Finally, the multi-directional force results were obtained. Compared with the individual directional force results, the output capacitance value of multi-directional force was lower, which indicated the amplitude decrease in capacity change in the normal and tangential direction. This might be caused by the deformation distribution in the normal and tangential direction under multi-directional force.

Tactile Sensing for Minimally Invasive Surgery: Conventional Methods and Potential Emerging Tactile Technologies

As opposed to open surgery procedures, minimally invasive surgery (MIS) utilizes small skin incisions to insert a camera and surgical instruments. MIS has numerous advantages such as reduced postoperative pain, shorter hospital stay, faster recovery time, and reduced learning curve for surgical trainees. MIS comprises surgical approaches, including laparoscopic surgery, endoscopic surgery, and robotic-assisted surgery. Despite the advantages that MIS provides to patients and surgeons, it remains limited by the lost sense of touch due to the indirect contact with tissues under operation, especially in robotic-assisted surgery. Surgeons, without haptic feedback, could unintentionally apply excessive forces that may cause tissue damage. Therefore, incorporating tactile sensation into MIS tools has become an interesting research topic. Designing, fabricating, and integrating force sensors onto different locations on the surgical tools are currently under development by several companies and research groups. In this context, electrical force sensing modality, including piezoelectric, resistive, and capacitive sensors, is the most conventionally considered approach to measure the grasping force, manipulation force, torque, and tissue compliance. For instance, piezoelectric sensors exhibit high sensitivity and accuracy, but the drawbacks of thermal sensitivity and the inability to detect static loads constrain their adoption in MIS tools. Optical-based tactile sensing is another conventional approach that facilitates electrically passive force sensing compatible with magnetic resonance imaging. Estimations of applied loadings are calculated from the induced changes in the intensity, wavelength, or phase of light transmitted through optical fibers. Nonetheless, new emerging technologies are also evoking a high potential of contributions to the field of smart surgical tools. The recent development of flexible, highly sensitive tactile microfluidic-based sensors has become an emerging field in tactile sensing, which contributed to wearable electronics and smart-skin applications. Another emerging technology is imaging-based tactile sensing that achieved superior multi-axial force measurements by implementing image sensors with high pixel densities and frame rates to track visual changes on a sensing surface. This article aims to review the literature on MIS tactile sensing technologies in terms of working principles, design requirements, and specifications. Moreover, this work highlights and discusses the promising potential of a few emerging technologies towards establishing low-cost, high-performance MIS force sensing.

Improving HRI with Force Sensing

In the future, in a society where robots and humans live together, HRI is an important field of research. While most human–robot-interaction (HRI) studies focus on appearance and dialogue, touch-communication has not been the focus of many studies despite the importance of its role in human–human communication. This paper investigates how and where humans touch an inorganic non-zoomorphic robot arm. Based on these results, we install touch sensors on the robot arm and conduct experiments to collect data of users’ impressions towards the robot when touching it. Our results suggest two main things. First, the touch gestures were collected with two sensors, and the collected data can be analyzed using machine learning to classify the gestures. Second, communication between humans and robots using touch can improve the user’s impression of the robots.

Comparison of the biomechanical parameters during drop jump on compliant and noncompliant surfaces: A new methodological approach

Objective: Bilateral plyometric training of the lower extremities has been shown to provide improvement in vertical force production. However, designing a proper plyometric training program and choosing the appropriate surface is critical, otherwise the risk of injury and lower extremity joint pathologies increases. The aim of this study was to compare biomechanical parameters between mini-trampoline and noncompliant surface during drop jumping. Materials and Methods: Thirty-four male adults participated in the study. Active markers were placed on the left knee, ankle and hip joints of the participants. Also, a force sensing resistor was placed under the participants’ left shoes. During drop jumping, the knee joint angles were recorded by the camera while a data set of reaction forces and loading rates were collected using a force sensing resistor. Data were compared with paired samples T-test. The level of significance was set at p ≤ 0.05. Results: The mean values of maximum reaction forces and loading rates were greater on the noncompliant surface (p < 0.001). Mean knee joint angles for frame at which the knee angle is minimum and the frames one before and one after the frame at which the minimum value is obtained were similar between surfaces, however, were found to be smaller on noncompliant surface for the remaining eight frames (p < 0.05). Conclusion: This study indicates that the range of bending values in the knee joint is greater on noncompliant surface compared to mini-trampoline during drop jump. Since the mini-trampoline resulted in lower reaction forces and loading rates, it can be used as an exercise equipment to minimize the injury risk of plyometric training.

Flexible mechanical metamaterials enabling soft tactile sensors with multiple sensitivities at multiple force sensing ranges

The majority of existing tactile sensors are designed to measure a particular range of force with a fixed sensitivity. However, some applications require tactile sensors with multiple task-relevant sensitivities at multiple ranges of force sensing. Inspired by the human tactile sensing capability, this paper proposes a novel soft tactile sensor based on mechanical metamaterials which exhibits multiple sensitivity regimes due to the step-by-step locking behaviour of its heterogenous multi-layered structure. By tuning the geometrical design parameters of the collapsible layers, each layer experiences locking behaviour under different ranges of force which provides different sensitivity of the sensor at different force magnitude. The integration of a magnetic-based transduction method with the proposed structure results in high design degrees of freedom for realising the desired contact force sensitivities and corresponding force sensing ranges. A systematic design procedure is proposed to select appropriate design parameters to produce the desired characteristics. Two example designs of the sensor structure were fabricated using widely available benchtop 3D printers and tested for their performance. The results showed the capability of the sensor in providing the desired characteristics in terms of sensitivity and force range and being realised in different shapes, sizes and number of layers in a single structure. The proposed multi-sensitivity soft tactile sensor has a great potential to be used in a wide variety of applications where different sensitivities of force measurement is required at different ranges of force magnitudes, from robotic manipulation and human–machine interaction to biomedical engineering and health-monitoring.

High-power short-duration versus standard-power standard-duration settings for repeat atrial fibrillation ablation

Introduction High-power short-duration (HPSD) ablation is a novel strategy using contact force-sensing catheters optimized for radiofrequency ablation for atrial fibrillation (AF). No study has directly compared HPSD versus standard-power standard-duration (SPSD) contact force-sensing settings in patients presenting for repeat ablation with AF recurrence after initial ablation. Methods We studied consecutive cases of patients with AF undergoing repeat ablation with SPSD or HPSD settings after their initial pulmonary vein isolation (PVI) with temperature controlled non-contact force, SPSD or HPSD settings between 6/23/14 and 3/4/20. Procedural data collected included radiofrequency ablation delivery time (RADT). Clinical data collected include sinus rhythm maintenance post-procedure. Results A total of 61 patients underwent repeat ablation (36 SPSD, 25 HPSD). A total of 51 patients (83.6%) were found to have pulmonary vein reconnections necessitating repeat isolation, 10 patients (16.4%) had durable PVI and ablation targeted non-PV sources. RADT was shorter when comparing repeat ablation using HPSD compared to SPSD (22 vs 35 min; p = 0.01). There was no difference in sinus rhythm maintenance by Kaplan–Meier survival analysis (log rank test p = 0.87), after 3 or 12-months between groups overall, and when stratified by AF type, left atrial volume index, CHA2DS2-VASc score, or left ventricular ejection fraction. Conclusion We demonstrated that repeat AF ablation with HPSD reduced procedure times with similar sinus rhythm maintenance compared to SPSD in those presenting for repeat ablation.