Force Sensing Surgical Scissor Blades using Fibre Bragg Grating Sensors

This thesis considers the development and analysis of unique sensorised surgical scissor blades for application in minimally invasive robotic surgery (MIRS). The lack of haptic (force and tactile) feedback to the user is currently an unresolved issue with modern MIRS systems. This thesis presents details on smart sensing scissor blades which enable the measurement of instrument-tissue interaction forces for the purpose of force reflection and tissue property identification. A review of current literature established that there exists a need for small compact, biocompatible, sterilisable and robust sensors which meet the demands of current MIRS instruments. Therefore, the sensorised blades exploit the strain sensing capabilities of a single fibre Bragg grating (FBG) sensor bonded to their surface. The nature and magnitude of the strain likely to be experienced by the blades, and consequently the FBG sensor, while cutting soft tissue samples were characterised through the use of an application specific test-bed. Using the sensorised blades to estimate fracture properties is proposed, hence two methods of extracting fracture toughness information from the test samples are assessed and compared. Investigations were carried out on the factors affecting the transfer of strain from the blade material to the core of the FBG sensor for surface mounted or partially embedded arrangements. Results show that adhesive bond length, thickness and stiffness need to be carefully specified when bonding FBG sensors to ensure effective strain transfer. Calibration and dynamic cutting experiments were carried out using the characterisation test-bed. The complex nature of the blade interaction forces were modelled, primarily for the purpose of decoupling the direct, lateral, friction and fracture strains experienced by the bonded FBG sensor during cutting. The modelled and experimental results show that the approach taken in sensorising the blade enables detailed cutting force data to be obtained and consequently leads to a unique method in estimating the kinetic friction coefficient for the blades. The forces measured using the FBG are validated against a commercial load cell used in the test-bed. This research work demonstrates that this unique approach of placing a single optical fibre onto the scissor blades can, in an unobtrusive manner, measure interblade friction forces and material fracture properties occurring at the blade-tissue interface

Desempenho mecânico e modelação numérica de ligações adesivas de materiais compósitos inovadores para aeronáutica

Dissertação de mestrado em European Master in Advanced Structural Analysis and Design using Composite MaterialsDevido ao impacto das viagens aéreas nas emissões de carbono, o setor da aviação busca materiais e tecnologias mais leves para reduzir emissões de CO2, NOx e ruído. Os materiais compósitos, substituindo estruturas tradicionais de alumínio em aeronaves, oferecem vantagens de peso, reduzindo o consumo de combustível e melhorando o desempenho. No entanto, a fixação de compósitos com elementos de fixação mecânicos, como parafusos e rebites, pode aumentar o peso estrutural. A ligação adesiva surge como uma solução potencial, proporcionando economia de peso sem comprometer a resistência. Existem desafios no desenho de ligações coladas adesivamente para compósitos, exigindo testes extensivos para determinar a resistência da ligação. A presente tese teve como objetivo investigar ligações adesivas entre materiais compósitos de carbono. O estudo envolveu a caracterização experimental do adesivo epóxi 3MTM Scotch-WeldTM (EC-9323) para obter propriedades mecânicas que possam ser usadas nas simulações numéricas de estruturas coladas. Com esse propósito, foram realizados quatro tipos de testes: i. testes de tracção, ii. testes de corte TAST (thick adherend shear test), iii. testes de corte DCB (double cantilever beam test) e iv. ensaios de flexão com entalhe no extremo (ENF). Adicionalmente, a resistência ao corte e ao descolamento de ligações adesivas compósito-compósito foram caracterizadas experimentalmente. Diferentes combinações de compósitos foram utilizando o adesivo epóxi 3MTM Scotch-WeldTM (EC-9323). Por fim, uma investigação numérica foi iniciada, que, de momento, está em estado embrionário e requer aprofundamento em estudos futuros. Os resultados dos testes caracterizaram eficazmente o adesivo, proporcionando uma compreensão abrangente da resistência de colagem e resistência ao descolamento em uniões compósito compósito. Em conclusão, os resultados obtidos neste estudo sobre uniões adesivas de compósitos de carbono sublinham a importância da seleção de materiais, processos de fabrico e tratamentos de superfície para alcançar as propriedades mecânicas e de fratura desejadas em uniões adesivas.The aviation sector is under growing pressure to enhance eco-efficiency due to air travel's impact on global carbon emissions. This has prompted a shift towards lighter materials and technologies to reduce CO2, NOx emissions, and noise. Composite materials are at the forefront of this movement, replacing traditional aluminium high-performance aircraft structures. Compared to metals, composites offer significant weight advantages, resulting in lower fuel consumption and improved aircraft performance. However, attaching composites with mechanical fasteners like bolts and rivets can increase structural weight. Adhesive bonding emerges as a potential solution, offering weight savings without compromising strength. Challenges persist in designing adhesively bonded joints for composites, requiring extensive testing to determine joint strength. The present thesis aimed to investigate adhesive joints between carbon composite materials. The study involved experimental characterisation of 3MTM Scotch-WeldTM (EC-9323) epoxy adhesive to obtain mechanical properties that can be further used for the numerical simulation of bonded structures. With this purpose, four tests were performed: i. bulk tensile test, ii. thick adherend shear test (TAST), iii. double cantilever beam test (DCB), and iv. end-notched flexure (ENF). Additionally, the single-lap shear bond and peel strengths of composite-to-composite adhesive joints were experimentally characterised. Various combinations of composites were bonded using 3MTM Scotch-WeldTM (EC-9323) epoxy adhesive. Finally, a numerical study has been initiated; however, it remains in its preliminary stages, necessitating more improvement through future research. The test results effectively characterised the adhesive, offering a comprehensive understanding of bond strength and peel resistance in composite-to-composite joints. In conclusion, the results obtained in this study of adhesive carbon composite joints highlight the importance of material selection, manufacturing processes, and surface treatments in achieving adhesive joints' desired mechanical and fracture properties

Characterisation and modification of optoelectronic substrate surfaces for enhanced adhesive flow control

Optoelectronics manufacturers are under continuous pressure for miniaturisation of optoelectronic modules. One route to further miniaturisation is to reduce the spacing between the optical and optoelectronic components in the optical path adhesively mounted to ceramic carriers. Flow control of the adhesives over the ceramic surface is then imperative. Uncontrolled wetting can lead to an excessive adhesive footprint which interferes in the application of other adhesives for subsequent components. However, insufficient wetting can lead to low strength bonds vulnerable to thermal fatigue and shear failure. The goal of the work was to minimise the potential for uncontrolled wetting while maintaining unmodified bond properties. In addition positional stability of adhered parts on cure and in-service must not be detrimentally affected. [Continues.

Novel fine pitch interconnection methods using metallised polymer spheres

There is an ongoing demand for electronics devices with more functionality while reducing size and cost, for example smart phones and tablet personal computers. This requirement has led to significantly higher integrated circuit input/output densities and therefore the need for off-chip interconnection pitch reduction. Flip-chip processes utilising anisotropic conductive adhesives anisotropic conductive films (ACAs/ACFs) have been successfully applied in liquid crystal display (LCD) interconnection for more than two decades. However the conflict between the need for a high particle density, to ensure sufficient the conductivity, without increasing the probability of short circuits has remained an issue since the initial utilization of ACAs/ACFs for interconnection. But this issue has become even more severe with the challenge of ultra-fine pitch interconnection. This thesis advances a potential solution to this challenge where the conductive particles typically used in ACAs are selectively deposited onto the connections ensuring conductivity without bridging. The research presented in this thesis work has been undertaken to advance the fundamental understanding of the mechanical characteristics of micro-sized metal coated polymer particles (MCPs) and their application in fine or ultra-fine pitch interconnections. This included use of a new technique based on an in-situ nanomechanical system within SEM which was utilised to study MCP fracture and failure when undergoing deformation. Different loading conditions were applied to both uncoated polymer particles and MCPs, and the in-situ system enables their observation throughout compression. The results showed that both the polymer particles and MCP display viscoelastic characteristics with clear strain-rate hardening behaviour, and that the rate of compression therefore influences the initiation of cracks and their propagation direction. Selective particle deposition using electrophoretic deposition (EPD) and magnetic deposition (MD) of Ni/Au-MCPs have been evaluated and a fine or ultra-fine pitch deposition has been demonstrated, followed by a subsequent assembly process. The MCPs were successfully positively charged using metal cations and this charging mechanism was analysed. A new theory has been proposed to explain the assembly mechanism of EPD of Ni/Au coated particles using this metal cation based charging method. The magnetic deposition experiments showed that sufficient magnetostatic interaction force between the magnetized particles and pads enables a highly selective dense deposition of particles. Successful bonding to form conductive interconnections with pre-deposited particles have been demonstrated using a thermocompression flip-chip bonder, which illustrates the applicable capability of EPD of MCPs for fine or ultra-fine pitch interconnection

2D photonic crystals to enhance up-conversion emission for silicon photovoltaics

This thesis investigates the application of 2D photonic crystals to enhance the emission of up-conversion layers to improve the efficiency of silicon photovoltaics. Two up-conversion material compositions are of particular interest in this work: erbium doped titanium dioxide (TiO2:Er) and erbium doped yttrium fluoride (YF3:Er). The 2D photonic crystals under investigation are composed of TiO2:Er and air; and YF3:Er and silicon. These nano-structures are investigated using both simulation and experimental methods. Further work in this thesis analyses the properties of the highly conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) for use as a transparent electrode and thin film electrically conductive adhesive for the application of silicon photovoltaics. The design and geometrical parameters for the 2D photonic crystals were optimised through simulations (plane wave expansion and finite-difference time-domain), before the structures were experimentally fabricated and optically characterised. The novel analysis of the refractive index of the prepared up-conversion materials using ellipsometry was a key step in the design of the photonic crystal structures. A maximum photoluminescence enhancement of 3.79 times was observed for the 980 nm emission profile, however this could not be successfully attributed to a photonic crystal effect. The optical, mechanical and electronic properties of PEDOT:PSS were characterised for thin film samples, using novel ellipsometry analysis

Soft Sensors in digital healthcare monitoring

Stretchable sensors are a class of materials with applications across research fields from healthcare to structural engineering. Despite the extensive research aiming to improve the performance of individual materials or components, stretchable sensor devices are difficult to implement because conventional electronic components, mainly used for processing, which are rigid, have to make contact with soft components reliable enough to withstand real-world usage. This thesis introduces a method for creating electrical contacts that can be robustly attached onto soft, stretchable conductive polymer composites on one side and soldered to metal wires on the other side. Mechanically robust electrical contacts were developed to interface (soft) silicone-based strain sensors with conventional (hard) solid-state electronics using a nanoporous silicon-copper contact. Contacts are mounted on custom-made and commercial soft strain sensitive silicone sensors. The contacts are shown to be reliable under large deformations, then compared with a commonly used alternative under real-world strain conditions. The layered structure of the device creates a complex electronic component deriving from the silicon-copper Schottky junction. This thesis tests the versatility of the technology through a series of real-world applications. The silicon-copper contacts were used to produce a series of proof-of-concept devices, including a wearable respiration monitor, leg band for exercise monitoring, and squeezable ball to monitor rehabilitation of patients with hand injuries or neurological disorders. The sensor is shown to operate and detect multiple modes of motion regardless of placement on the body. Next, a proof-of-concept device was employed to measure hand grip strength. The optimized sensor can detect grip strength with high sensitivity. The hardness of the device was shown to increase sensitivity when healthy humans performed manual exercises and completed digital tasks. Providing patients with these devices can help monitor their rehabilitation following hand injuries or neurological disorders. This can be done through self-led at-home therapy which has been shown to improve treatment, engagement, long-term lifestyle adherence, while avoiding repeated visits to clinics which plays an important role in frequency of therapy, effectiveness, and accessibility.Open Acces

Characterization and improvement of copper / glass adhesion

The development of glass substrates for use as an alternative to printed circuit boards (PCBs) attracts significant industrial attention, because of the potential for low cost but high performance interconnects and optical connection. Electroless plating is currently used to deposit conductive tracks on glass substrates and the quality of copper / glass adhesion is a key functional issue. Without adequate adhesive strength the copper plating will prematurely fail. Existing studies have covered the relationship between surface roughness and adhesion performance, but few of them have considered the detail of surface topography in any depth. This research is specifically considering the mechanical contribution of the glass surface texture to the copper / glass adhesive bond, and attempting to isolate new ISO 25178 areal surface texture parameters that can describe these surfaces. Excimer laser machining has been developed and used to create a range of micro pattern structured surfaces on CMG glass substrates. Excimer mask dimensions and laser operation parameters have been varied and optimized according to surface topography and adhesion performance of the samples. Non-contact surface measurement equipment (Zygo NewView 5000 coherence scanning interferometry) has been utilized to measure and parameterize (ISO 25178) the surface texture of the glass substrates before electroless copper metallization. Copper adhesion quality has been tested using quantitative scratch testing techniques, providing an identification of the critical load of failure for different plated substrates. This research is establishing the statistical quality of correlation between the critical load values and the associated areal parameters. In this thesis, the optimal laser processing parameter settings for CMG glass substrate machining and the topographic images of structured surfaces for achieving strong copper / glass plating adhesion are identified. The experimental relationships between critical load and areal surface parameters, as well as the discussions of a theoretical approach are presented. It is more significant to consider Sq, Sdq, Sdr, Sxp, Vv, Vmc and Vvc to describe glass substrate surface topography and the recommended data value ranges for each parameter have been identified to predict copper / plating adhesion performance