The effect of indentation force and displacement on visual perception of compliance

This paper investigates the effect of maximum indentation force and depth on people's ability to accurately discriminate compliance using indirect visual information only. Participants took part in two psychophysical experiments in which they were asked to choose the 'softest' sample out of a series of presented sample pairs. In the experiments, participants observed a computer-actuated tip indent the sample pairs to one of two conditions; maximum depth (10mm) or maximum force (4N). This indentation process simulates tool operated palpation in laparoscopic surgery. Results were used to plot psychometric functions as a measure of accuracy of compliance discriminability. A comparison indicated that participants performed best in the task where they judged samples being indented to a pre-set maximum force relying solely on visual cues, which demonstrates the effect of visual information on compliance discrimination. Results also show that indentation cues such as force and deformation depth have different effects on our ability to visually discriminate compliance. These findings will inform future work on designing a haptic feedback system capable of augmenting visual and haptic information independently for optimal compliance discrimination performance

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

Child-led, Creative Exploration of Paediatric Incontinence

This paper describes a novel collaboration between a health science initiative, a MedTech Co-operative and a university design research department alongside a group of children with incontinence, their parents and siblings. This collaboration hoped to inform the development of technological interventions specifically aimed at supporting paediatric incontinence. Together, we used a range of bespoke tools to creatively and collaboratively explore questions of ‘What are your main challenges? How do you currently address them? And how would you like to address them in the future?’ These tools aimed to place the children as the experts in the rooms, reflecting on their wider life (i.e. their hobbies, friends, family) and took an asset-based approach to highlight the skills and resources they already leverage to address their personal challenges. Later, ideation activities were used to empower the families as inventors to highlight and address any unmet health needs. Central to each of the activities was the aim to reframe a traditionally ‘taboo’ topic as something that is safe, and even fun, to explore through creative means. This study concludes that by using context-specific, sensitive and creative tools, children from a range of ages can (and should) be included in setting the agenda for future healthcare technology development, even in topics that are traditionally difficult to discuss

A soft multi-axial force sensor to assess tissue properties in RealTime

Objective: This work presents a method for the use of a soft multi-axis force sensor to determine tissue trauma in Minimally Invasive Surgery. Despite recent developments, there is a lack of effective haptic sensing technology employed in instruments for Minimally Invasive Surgery (MIS). There is thus a clear clinical need to increase the provision of haptic feedback and to perform real-time analysis of haptic data to inform the surgical operator. This paper establishes a methodology for the capture of real-time data through use of an inexpensive prototype grasper. Fabricated using soft silicone and 3D printing, the sensor is able to precisely detect compressive and shear forces applied to the grasper face. The sensor is based upon a magnetic soft tactile sensor, using variations in the local magnetic field to determine force. The performance of the sensing element is assessed and a linear response was observed, with a max hysteresis error of 4.1% of the maximum range of the sensor. To assess the potential of the sensor for surgical sensing, a simulated grasping study was conducted using ex vivo porcine tissue. Two previously established metrics for prediction of tissue trauma were obtained and compared from recorded data. The normalized stress rate (kPa.mm⁻¹) of compression and the normalized stress relaxation (ΔσR) were analyzed across repeated grasps. The sensor was able to obtain measures in agreement with previous research, demonstrating future potential for this approach. In summary this work demonstrates that inexpensive soft sensing systems can be used to instrument surgical tools and thus assess properties such as tissue health. This could help reduce surgical error and thus benefit patients

A novel multiple electrode direct current technique for characterisation of tissue resistance during surgery

Electrochemical and electrical characteristics have the potential to help differentiate between, and assess the health state of, different biological tissues. However, measurement and interpretation of these characteristics is non-trivial. We propose a new DC galvanostatic sensing method for application to laparoscopic cancer surgery. This presents a simple and cost-effective measurement coupled with straightforward data interpretation. This paper describes the electrochemical and electrical theory underpinning the technique. Additionally, we describe a measurement system employing this technique and present an investigation into the feasibility of using it for measuring the resistance of different tissue types. Measurements were performed on ex vivo porcine liver, colon and rectum tissues. Outputs were consistent with theory and showed a significant difference between the resistance of the different tissue types, (one-way ANOVA, F(2, 28) = 1369, p < 0.01). These findings indicate that this novel technique may be viable as a low cost method for the discrimination and health assessment of tissues in clinical scenarios

A physical simulation to investigate the effect of anorectal angle on continence

This paper investigates the effect of the anorectal angle on continence using a physical model of the anatomical system. A method to fabricate, measure and control a physical model for the simulation of human faecal continence is presented. A model rectum and associated soft tissues, based on geometry from an anonymised CT dataset, was fabricated from silicone and showed behavioural realism to ex vivo tissue. Simulated stool matter with similar rheological properties to human faeces was developed. Instrumentation and control hardware are used to regulate injection of simulated stool into the system, define the anorectal angle and monitor stool flow rate, intra-rectal pressure and puborectalis force. A study was then conducted in which simulated stool was introduced to the system for anorectal angles between 80° and 100°. Results obtained from the study give insight into the effect of the anorectal angle on continence. Stool leakage was reduced as the angle became more acute. Conversely, intra-rectal pressure increased. These data demonstrate that the anorectal angle is fundamental in maintaining continence. This work is valuable in helping improve our understanding of the physical behaviour of the faecal system. It has particular relevance facilitating improved technologies to treat or manage severe faecal incontinence

The impact of electrode resistance on the biogalvanic characterisation technique

Measurement of a tissue-specific electrical resistance may offer a discriminatory metric for evaluation of tissue health during cancer surgery. With a move toward minimally invasive procedures, applicable contact sensing modalities must be scalable, fast and robust. A passive resistance characterisation method utilising a biogalvanic cell as an intrinsic power source has been proposed as a potentially suitable solution. Previous work has evaluated this system with results showing effective discrimination of tissue type and damage (through electroporation). However, aspects of the biogalvanic cell have been found to influence the characterisation performance, and are not currently accounted for within the system model. In particular, the electrode and salt-bridge resistance are not independently determined, leading to over predictions of tissue resistivity. This paper describes a more comprehensive model and characterisation scheme, with electrode parameters and salt-bridge resistivity being evaluated independently. In a generalised form, the presented model illustrates how the relative resistive contributions from the electrodes and medium relate to the existing characterisation method efficacy. We also describe experiments with physiologically relevant salt solutions (1.71, 17.1, 154 mM), used for validation and comparison. The presented model shows improved performance over the current biogalvanic measurement technique at the median conductivity. Both systems become unable to predict conductivity accurately at high conductivity due to the dominance of the electrode parameters. The characterisation techniques have also been applied to data collected on freshly excised human colon tissue (healthy and cancerous). The findings suggest that the resistance of the cell under the test conditions is electrode dominated, leading to erroneous tissue resistance determination. Measurement optimisation strategies and the surgical applicability of the biogalvanic technique are discussed in light of these findings

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

Hybrid Position and Orientation Tracking for a Passive Rehabilitation Table-Top Robot

This paper presents a real time hybrid 2D position and orientation tracking system developed for an upper limb rehabilitation robot. Designed to work on a table-top, the robot is to enable home-based upper-limb rehabilitative exercise for stroke patients. Estimates of the robot's position are computed by fusing data from two tracking systems, each utilizing a different sensor type: laser optical sensors and a webcam. Two laser optical sensors are mounted on the underside of the robot and track the relative motion of the robot with respect to the surface on which it is placed. The webcam is positioned directly above the workspace, mounted on a fixed stand, and tracks the robot's position with respect to a fixed coordinate system. The optical sensors sample the position data at a higher frequency than the webcam, and a position and orientation fusion scheme is proposed to fuse the data from the two tracking systems. The proposed fusion scheme is validated through an experimental set-up whereby the rehabilitation robot is moved by a humanoid robotic arm replicating previously recorded movements of a stroke patient. The results prove that the presented hybrid position tracking system can track the position and orientation with greater accuracy than the webcam or optical sensors alone. The results also confirm that the developed system is capable of tracking recovery trends during rehabilitation therapy

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