Development and Characterisation of a Multi-material 3D Printed Torsion Spring

Compliant actuation methods are popular in robotics applications where interaction with complex and unpredictable environments and objects is required. There are a number of ways of achieving this, but one common method is Series Elastic Actuation (SEA). In a recent version of their Unified Snake robot, Choset et al. incorporated a Series Elastic Element (SEE) in the form of a rubber torsional spring. This pa- per explores the possibility of using multi-material 3D printing to produce similar SEEs. This approach would facilitate the fabrication and testing of different spring variants and minimise the assembly required. This approach is evaluated by characterizing the behavior of two printed SEEs with different dimensions. The springs exhibit predictable viscoelastic behavior that is well described by a five element Wiechert model. We find that individual springs behave predictably and that multiple copies of the same spring design exhibit good consistency

The use of polymeric meshes for Pelvic Organ Prolapse: current concepts, challenges and future perspectives

Pelvic organ prolapse (POP) is one of the most common chronic disorders in women, impacting the quality of life of millions of them worldwide. More than 100 surgical procedures have been developed over the decades to treat POP. However, the failure of conservative strategies and the number of patients with recurrence risk have increased the need for further adjuvant treatments. Since their introduction, surgical synthetic meshes have dramatically transformed POP repair showing superior anatomic outcomes in comparison to traditional approaches. Although significant progress has been attained, among the meshes in clinical use, there is no single mesh appropriate for every surgery. Furthermore, due to the risk of complications including acute and chronic infection, mesh shrinkage, and erosion of the tissue, the benefits of the use of meshes have recently been questioned. The aim of this work is to review the evolution of POP surgery, analyzing the current challenges, and detailing the key factors pertinent to the design of new mesh systems. Starting with a description of the pelvic floor anatomy, the article then presents the traditional treatments used in pelvic organ disorders. Next, the development of synthetic meshes is described with an insight into how their function is dependent on both mesh design variables (i.e., material, structure, and functional treatment) and surgical applications. These are then linked to common mesh‐related complications, and an indication of current research aiming to address these issues

A low-cost, high-performance, soft tri-axis tactile sensor based on eddy-current effect

Tactile sensors are essential for robotic systems to interact safely and effectively with the external world. In particular, tri-axis tactile sensors are crucial for dexterous robotic manipulations by providing shear force for slip and contact angle detection. In this paper, we present a soft tri-axis tactile sensors using flexible coils and conductive films based on eddy-current effect. Prototypes were developed, calibrated and evaluated, which achieved a force measurement resolution of 0.3 mN in each axis, with a bandwidth up to 1 kHz. The presented sensor is low-cost, robust, durable, and easily customizable for a variety of robotic and healthcare applications

Thin soft layered actuator based on a novel fabrication technique

This paper presents a novel fabrication method for constructing thin soft layered actuators. The method is based on building up thin layers of elastomeric material with embedded strain-limiting and mask layers using a bespoke film applicator. This enables the fabrication of millimetre-scale soft actuators with complex integrated masks and/or strain-limiting layers, as demonstrated in a series of proof of concept prototypes. The prototype actuators can be cut into a desired shape via laser cutting the laminated sheet. This paper shows the feasibility of the fabrication method and the value of its use in creating thin soft layered actuators for application in soft robotics. The technique can be further developed to fabricate multi-material composite soft actuators which are thin, compact, flexible and stretchable

Engineering Incipient Slip Into Surgical Graspers to Enhance Grasp Performance

The surgical community has long reported the need for improved control of surgical graspers when handling delicate soft tissues, both to avoid the over application of force which leads to trauma, and to avoid tissue slip. The majority of research has sought to mitigate these issues through the integration of force feedback into the graspers. In this work we investigate an alternative strategy in which the grasper design is engineered to create preferential localised slip, also known as incipient slip, on the premise that this can be detected before the onset of macro slip, allowing graspers to use the minimum force required to maintain stable control. We demonstrate the ability to encourage incipient slip in a predictable and repeatable manner through the design of the grasper face profile and pattern. This provides an important foundation for development of sensing systems capable of detecting these slips during surgery to improve operative outcomes

The impact of visual cues on haptic compliance discrimination using a pseudo-haptic robotic system

A psychophysical magnitude estimation experiment was set up to determine the extent of the contribution of visual feedback during haptic compliance discrimination. Subjects remotely palpated physical compliant samples using a novel pseudo-haptic feedback system which allowed for independent manipulation of visual and haptic feedback. Subjects were asked to rate the compliance of a test sample based on that of a reference sample. While visual feedback was modified by switching the physical test samples shown to participants during indentation, haptic compliance of the test samples was always identical to that of the reference sample. Any variations in haptic sensation was a result of pseudo-haptic illusions. Ratings were collated and fitted to Steven's power law as well as Weber's law. A 0.18 power exponent suggests that the system was successful in generating viscoelastic properties through variations in visual information only. A 19.6% visual change from the reference compliance was necessary in order to perceive a change in haptic compliance using the pseudo-haptic system. These findings could prove beneficial in research and educationalfacilities where advanced force feedback devices are limited or inaccessible, where the concept of pseudo-haptics could be used to simulate various mechanical properties of virtual tissue for training purposes without the needfor complicated or costly force feedback

An inductive force sensor for in-shoe plantar normal and shear load measurement

Diabetic foot ulcers (DFUs) are a severe global public health issue. Plantar normal and shear load are believed to play an important role in the development of foot ulcers and could be a valuable indicator to improve assessment of DFUs. However, despite their promise, plantar load measurements currently have limited clinical application, primarily due to the lack of reliable measurement techniques particularly for shear load measurements. In this paper we report on the design and evaluation of a novel tri-axis force sensor to measure both normal and shear load on the foot’s plantar surface simultaneously. The sensor consists of a group of inductive sensing coils above which a conductive target is placed on a hyperelastic elastomer. Movement of the target under load affects the coil inductances which are measured and digitized by an embedded system. Using a computational finite element model, we investigated the influence of sensing coil form and configuration on sensor performance. A sensor configured with four-square coils and maximal turns provided the best performance for plantar load measurements. A prototype was fabricated and calibrated using a neural network to map the non-linear relationship between the sensor output and the applied tri-axis load. Experimental evaluation indicates that the tri-axis sensor can effectively detect shear load of �16 N and normal load up to 105 N (RMS errors: 1.05 N and 1.73 N respectively) with a high performance. Overall, this sensor provides a promising basis for plantar normal and shear load measurement which are crucial for improved assessment of DFU

RollerBall: a mobile robot for intraluminal locomotion

There are currently a number of major drawbacks to using a colonoscope that limit its efficacy. One solution to this may be to use a warm liquid to distend the colon during inspection. Another is to replace the colonoscope with a small mobile robot – a solution many believe is the future of gastrointestinal intervention. This paper presents RollerBall, an intraluminal robot that uses wheeled-locomotion to traverse the length of a fluid-filled colon. The device provides a central, stable platform within the lumen for the use of diagnostic and therapeutic tools. The concept is described in detail and the feasibility demonstrated in a series of tests in a synthetic colon

Design and Characterization of Tri-axis Soft Inductive Tactile Sensors

Tactile sensors are essential for robotic systems to safely and effectively interact with the environment and humans. In particular, tri-axis tactile sensors are crucial for dexterous robotic manipulations by providing shear force, slip or contact angle information. The Soft Inductive Tactile Sensor (SITS) is a new type of tactile sensor that measures inductance variations caused by eddy-current effect. In this paper, we present a soft tri-axis tactile sensor using the configuration of four planar coils and a single conductive film with hyperelastic material in between them. The working principle is explained and design methods are outlined. A 3D finite element model was developed to characterize the tri-axis SITS and to optimize the target design through parameter study. Prototypes were fabricated, characterized and calibrated, and a force measurement resolution of 0.3 mN is achieved in each axis. Demonstrations show that the sensor can clearly measure light touch (a few mN normal force) and shear force pulses (10 to 30 mN) produced by a serrated leaf when it is moved across the sensor surface. The presented sensor is low cost, high performance, robust, durable, and easily customizable for a variety of robotic and healthcare applications

Utilising Incipient Slip for Grasping Automation in Robot Assisted Surgery

Despite recent advances in modern surgical robotic systems, an ongoing challenge remains their limited ability to control grasp force. This can impair surgical performance as a result of either tissue slippage or trauma from excessive grasp force. In this work we investigate a force control strategy to address this challenge based on the detection of incipient slip. Our approach employs a grasper face whose shape is engineered to encourage preferential localised slips that can be sensed using embedded displacement sensors prior to gross slip occurring. This novel approach enables closed loop control of the grasping force to prevent gross slip whilst applying minimal force. In this paper we first demonstrate the efficacy of sensing incipient slip and then demonstrate how this can form a robust closed loop grasping system to maintain stable control of tissue. Results demonstrate that this approach can achieve equivalent grasping performance to a scheme employing a fixed maximal grasping force while reducing tissue loading, and thus risk of trauma. This provides the foundation for the development of automated surgical robots with adaptive grasp force control