Smart materials for subsea buoyancy control

Buoyancy control is needed in small autonomous underwater devices to enable greater flexibility in measurements in the ocean. This project has examined a number of ways in which buoyancy changes might be achieved. Firstly, an extensive review of the mechanisms by which various marine organisms control their buoyancy was undertaken. There is a tremendous diversity of natural buoyancy control mechanisms, but most of these mechanisms produce only slow (and small) changes in buoyancy.Studies were carried out on the behaviour of polymer gel systems that exhibit large volume changes under the influence of solvent composition and/or temperature. The effects of salinity were investigated, from 5 parts per thousand (ppt) to 35ppt, on hydrolysed polyacrylamide gels, over the temperature range of 5°C to 40°C. It was found that the gels decreased in volume in the solutions, this effect being most pronounced in the 35ppt solution. As temperature increased, the volume changes were observed to decrease. The cyclical volumetric strain behaviour of the polyacrylamide gels, by alternate exposure to saline solutions and distilled water, resulted in significant (~200%) volume changes induced over periods of 2 days. In a second study, the density change associated with the volumetric strain of polymeric materials was investigated in poly(N-isopropylacrylamide), NIPA, gels. The temperature-sensitive NIPA gels, immersed in distilled water or seawater solutions at temperatures ranging from 5°C to 50°C, exhibited volume changes of over 800%, and density changes of 30-40%. NIPA gels exhibit a faster response time than polyacrylamide gels, and their density and volume changes have potential application in buoyancy change.Experiments were also performed on NiTi shape memory alloys (SMA), which change in length and mechanical properties with temperature. A controllable parallel-plate device was constructed, linked by four helical SMA springs, which exerted significant axial forces with the application of temperature. The device is capable of producing substantial volume changes if contained in a suitable enclosure. It is currently on loan to the Science Museum, London, as part of a new exhibition of the Wellcome Wing

Functional Soft Robotic Actuators Based on Dielectric Elastomers

Dielectric elastomer actuators (DEAs) are a promising soft actuator technology for robotics. Adding robotic functionalities--folding, variable stiffness, and adhesion--into their actuator design is a novel method to create functionalized robots with simplified actuator configurations. We first propose a foldable actuator that has a simple antagonistic DEA configuration allowing bidirectional actuation and passive folding. To prove the concept, a foldable elevon actuator with outline size of 70 mm × 130 mm is developed with a performance specification matched to a 400 mm wingspan micro air vehicle (MAV) of mass 130 g. The developed actuator exhibits actuation angles up to ± 26 ° and a torque of 2720 mN·mm in good agreement with a prediction model. During a flight, two of these integrated elevon actuators well controlled the MAV, as proven by a strong correlation of 0.7 between the control signal and the MAV motion. We next propose a variable stiffness actuator consisting of a pre-stretched DEA bonded on a low-melting-point alloy (LMPA) embedded silicone substrate. The phase of the LMPA changes between liquid and solid enabling variable stiffness of the structure, between soft and rigid states, while the DEA generates a bending actuation. A proof-of-concept actuator with dimension 40 mm length × 10mm width × 1mm thickness and a mass of 1 g is fabricated and characterized. Actuation is observed up to 47.5 ° angle and yielding up to 2.4 mN of force in the soft state. The stiffness in the rigid state is ~90 × larger than an actuator without LMPA. We develop a two-finger gripper in which the actuators act as the fingers. The rigid state allows picking up an object mass of 11 g (108 mN), to be picked up even though the actuated grasping force is only 2.4 mN. We finally propose an electroadhesion actuator that has a DEA design simultaneously maximizing electroadhesion and electrostatic actuation, while allowing self-sensing by employing an interdigitated electrode geometry. The concept is validated through development of a two-finger soft gripper, and experimental samples are characterized to address an optimal design. We observe that the proposed DEA design generates 10 × larger electroadhesion force compared to a conventional DEA design, equating to a gripper with a high holding force (3.5 N shear force for 1 cm^2) yet a low grasping force (1 mN). These features make the developed simple gripper to handle a wide range of challenging objects such as highly-deformable water balloons (35.6 g), flat paper (0.8 g), and a raw chicken egg (60.9 g), with its lightweight (1.5 g) and fast movement (100 ms to close fingers). The results in this thesis address the creation of the functionalized robots and expanding the use of DEAs in robotics

Hydrogel-based logic circuits for planar microfluidics and lab-on-a-chip automation

The transport of vital nutrient supply in fluids as well as the exchange of specific chemical signals from cell to cell has been optimized over billion years of natural evolution. This model from nature is a driving factor in the field of microfluidics, which investigates the manipulation of the smallest amounts of fluid with the aim of applying these effects in fluidic microsystems for technical solutions. Currently, microfluidic systems are receiving attention, especially in diagnostics, \textit{e.g.} as SARS-CoV-2 antigen tests, or in the field of high-throughput analysis, \textit{e.g.} for cancer research. Either simple-to-use or large-scale integrated microfluidic systems that perform biological and chemical laboratory investigations on a so called Lab-on-a-Chip (LoC) provide fast analysis, high functionality, outstanding reproducibility at low cost per sample, and small demand of reagents due to system miniaturization. Despite the great progress of different LoC technology platforms in the last 30 years, there is still a lack of standardized microfluidic components, as well as a high-performance, fully integrated on-chip automation. Quite promising for the microfluidic system design is the similarity of the Kirchhoff's laws from electronics to predict pressure and flow rate in microchannel structures. One specific LoC platform technology approach controls fluids by active polymers which respond to specific physical and chemical signals in the fluid. Analogue to (micro-)electronics, these active polymer materials can be realized by various photolithographic and micro patterning methods to generate functional elements at high scalability. The so called chemofluidic circuits have a high-functional potential and provide “real” on-chip automation, but are complex in system design. In this work, an advanced circuit concept for the planar microfluidic chip architecture, originating from the early era of the semiconductor-based resistor-transistor-logic (RTL) will be presented. Beginning with the state of the art of microfluidic technologies, materials, and methods of this work will be further described. Then the preferred fabrication technology is evaluated and various microfluidic components are discussed in function and design. The most important component to be characterized is the hydrogel-based chemical volume phase transition transistor (CVPT) which is the key to approach microfluidic logic gate operations. This circuit concept (CVPT-RTL) is robust and simple in design, feasible with common materials and manufacturing techniques. Finally, application scenarios for the CVPT-RTL concept are presented and further development recommendations are proposed.:1 The transistor: invention of the 20th century 2 Introduction to fluidic microsystems and the theoretical basics 2.1 Fluidic systems at the microscale 2.2 Overview of microfluidic chip fabrication 2.2.1 Common substrate materials for fluidic microsystems 2.2.2 Structuring polymer substrates for microfluidics 2.2.3 Polymer chip bonding technologies 2.3 Fundamentals and microfluidic transport processes 2.3.1 Fluid dynamics in miniaturized systems 2.3.2 Hagen-Poiseuille law: the fluidic resistance 2.3.3 Electronic and microfluidic circuit model analogy 2.3.4 Limits of the electro-fluidic analogy 2.4 Active components for microfluidic control 2.4.1 Fluid transport by integrated micropumps 2.4.2 Controlling fluids by on-chip microvalves 2.4.3 Hydrogel-based microvalve archetypes 2.5 LoC technologies: lost in translation? 2.6 Microfluidic platforms providing logic operations 2.6.1 Hybrids: MEMS-based logic concepts 2.6.2 Intrinsic logic operators for microfluidic circuits 2.7 Research objective: microfluidic hydrogel-based logic circuits 3 Stimuli-responsive polymers for microfluidics 3.1 Introduction to hydrogels 3.1.1 Application variety of hydrogels 3.1.2 Hydrogel microstructuring methods 3.2 Theory: stimuli-responsive hydrogels 3.3 PNIPAAm: a multi-responsive hydrogel 4 Design, production and characterization methods of hydrogel-based microfluidic systems 4.1 The semi-automated computer aided design approach for microfluidic systems 4.2 The applied design process 4.3 Fabrication of microfluidic chips 4.3.1 Photoresist master fabrication 4.3.2 Soft lithography for PDMS chip production 4.3.3 Assembling PDMS chips by plasma bonding 4.4 Integration of functional hydrogels in microfluidic chips 4.4.1 Preparation of a monomer solution for hydrogel synthesis 4.4.2 Integration methods 4.5 Effects on hydrogel photopolymerization and the role of integration method 4.5.1 Photopolymerization from monomer solutions: managing the diffusion of free radicals 4.5.2 Hydrogel adhesion and UV light intensity distribution in the polymerization chamber 4.5.3 Hydrogel shrinkage behavior of different adhesion types 4.6 Comparison of the integration methods 4.7 Characterization setups for hydrogel actuators and microfluidic measurements . 71 4.7.1 Optical characterization method to describe swelling behavior 4.7.2 Setup of a microfluidic test stand 4.8 Conclusion: design, production and characterization methods 5 VLSI technology for hydrogel-based microfluidics 5.1 Overview of photolithography methods 5.2 Standard UV photolithography system for microfluidic structures 5.3 Self-made UV lithography system suitable for the mVLSI 5.3.1 Lithography setup for the DFR and SU-8 master exposure 5.3.2 Comparison of mask-based UV induced crosslinking for DFR and SU-8 5.4 Mask-based UV photopolymerization for mVLSI hydrogel patterning 5.4.1 Lithography setup for the photopolymerization of hydrogels 5.4.2 Hydrogel photopolymerization: experiments and results 5.4.3 Troubleshooting: photopolymerization of hydrogels 5.5 Conclusion: mVLSI technologies for hydrogel-based LoCs 6 Components for chemofluidic circuit design 6.1 Passive components in microfluidics 6.1.1 Microfluidic resistor 6.1.2 Planar-passive microfluidic signal mixer 6.1.3 Phase separation: laminar flow signal splitter 6.1.4 Hydrogel-based microfluidic one-directional valves 6.2 Hydrogel-based active components 6.2.1 Reversible hydrogel-based valves 6.2.2 Hydrogel-based variable resistors 6.2.3 CVPT: the microfluidic transistor 6.3 Conclusion: components for chemofluidic circuits 7 Hydrogel-based logic circuits in planar microfluidics 7.1 Development of a planar CVPT logic concept 7.1.1 Challenges of planar microfluidics 7.1.2 Preparatory work and conceptional basis 7.2 The microfluidic CVPT-RTL concept 7.3 The CVPT-RTL NAND gate 7.3.1 Circuit optimization stabilizing the NAND operating mode 7.3.2 Role of laminar flow for the CVPT-RTL concept 7.3.3 Hydrogel-based components for improved switching reliability 7.4 One design fits all: the NOR, AND and OR gate 7.5 Control measures for cascaded systems 7.6 Application scenarios for the CVPT-RTL concept 7.6.1 Use case: automated cell growth system 7.6.2 Use case: chemofluidic converter 7.7 Conclusion: Hydrogel-based logic circuits 8 Summary and outlook 8.1 Scientific achievements 8.2 Summarized recommendations from this work Supplementary information SI.1 Swelling degree of BIS-pNIPAAm gels SI.2 Simulated ray tracing of UV lithography setup by WinLens® SI.3 Determination of the resolution using the intercept theorem SI.4 Microfluidic master mold test structures SI.4.1 Polymer and glass mask comparison SI.4.2 Resolution Siemens star in DFR SI.4.3 Resolution Siemens star in SU-8 SI.4.4 Integration test array 300 μm for DFR and SU-8 SI.4.5 Integration test array 100 μm for SU-8 SI.4.6 Microfluidic structure for different technology parameters SI.5 Microfluidic test setups SI.6 Supplementary information: microfluidic components SI.6.1 Compensation methods for flow stabilization in microfluidic chips SI.6.2 Planar-passive microfluidic signal mixer SI.6.3 Laminar flow signal splitter SI.6.4 Variable fluidic resistors: flow rate characteristics SI.6.5 CVPT flow rate characteristics for high Rout Standard operation proceduresDer Transport von lebenswichtigen Nährstoffen in Flüssigkeiten sowie der Austausch spezifischer chemischer Signale von Zelle zu Zelle wurde in Milliarden Jahren natürlicher Evolution optimiert. Dieses Vorbild aus der Natur ist ein treibender Faktor im Fachgebiet der Mikrofluidik, welches die Manipulation kleinster Flüssigkeitsmengen erforscht um diese Effekte in fluidischen Mikrosystemen für technische Lösungen zu nutzen. Derzeit finden mikrofluidische Systeme vor allem in der Diagnostik, z.B. wie SARS-CoV-2-Antigentests, oder im Bereich der Hochdurchsatzanalyse, z.B. in der Krebsforschung, besondere Beachtung. Entweder einfach zu bedienende oder hochintegrierte mikrofluidische Systeme, die biologische und chemische Laboruntersuchungen auf einem sogenannten Lab-on-a-Chip (LoC) durchführen, bieten schnelle Analysen, hohe Funktionalität, hervorragende Reproduzierbarkeit bei niedrigen Kosten pro Probe und einen geringen Bedarf an Reagenzien durch die Miniaturisierung des Systems. Trotz des großen Fortschritts verschiedener LoC-Technologieplattformen in den letzten 30 Jahren mangelt es noch an standardisierten mikrofluidischen Komponenten sowie an einer leistungsstarken, vollintegrierten On-Chip-Automatisierung. Vielversprechend für das Design mikrofluidischer Systeme ist die Ähnlichkeit der Kirchhoff'schen Gesetze aus der Elektronik zur Vorhersage von Druck und Flussrate in Mikrokanalstrukturen. Ein spezifischer Ansatz der LoC-Plattformtechnologie steuert Flüssigkeiten durch aktive Polymere, die auf spezifische physikalische und chemische Signale in der Flüssigkeit reagieren. Analog zur (Mikro-)Elektronik können diese aktiven Polymermaterialien durch verschiedene fotolithografische und mikrostrukturelle Methoden realisiert werden, um funktionelle Elemente mit hoher Skalierbarkeit zu erzeugen.\\ Die sogenannten chemofluidischen Schaltungen haben ein hohes funktionales Potenzial und ermöglichen eine 'wirkliche' on-chip Automatisierung, sind jedoch komplex im Systemdesign. In dieser Arbeit wird ein fortgeschrittenes Schaltungskonzept für eine planare mikrofluidische Chiparchitektur vorgestellt, das aus der frühen Ära der halbleiterbasierten Resistor-Transistor-Logik (RTL) hervorgeht. Beginnend mit dem Stand der Technik der mikrofluidischen Technologien, werden Materialien und Methoden dieser Arbeit näher beschrieben. Daraufhin wird die bevorzugte Herstellungstechnologie bewertet und verschiedene mikrofluidische Komponenten werden in Funktion und Design diskutiert. Die wichtigste Komponente, die es zu charakterisieren gilt, ist der auf Hydrogel basierende chemische Volumen-Phasenübergangstransistor (CVPT), der den Schlüssel zur Realisierung mikrofluidische Logikgatteroperationen darstellt. Dieses Schaltungskonzept (CVPT-RTL) ist robust und einfach im Design und kann mit gängigen Materialien und Fertigungstechniken realisiert werden. Zuletzt werden Anwendungsszenarien für das CVPT-RTL-Konzept vorgestellt und Empfehlungen für die fortlaufende Entwicklung angestellt.:1 The transistor: invention of the 20th century 2 Introduction to fluidic microsystems and the theoretical basics 2.1 Fluidic systems at the microscale 2.2 Overview of microfluidic chip fabrication 2.2.1 Common substrate materials for fluidic microsystems 2.2.2 Structuring polymer substrates for microfluidics 2.2.3 Polymer chip bonding technologies 2.3 Fundamentals and microfluidic transport processes 2.3.1 Fluid dynamics in miniaturized systems 2.3.2 Hagen-Poiseuille law: the fluidic resistance 2.3.3 Electronic and microfluidic circuit model analogy 2.3.4 Limits of the electro-fluidic analogy 2.4 Active components for microfluidic control 2.4.1 Fluid transport by integrated micropumps 2.4.2 Controlling fluids by on-chip microvalves 2.4.3 Hydrogel-based microvalve archetypes 2.5 LoC technologies: lost in translation? 2.6 Microfluidic platforms providing logic operations 2.6.1 Hybrids: MEMS-based logic concepts 2.6.2 Intrinsic logic operators for microfluidic circuits 2.7 Research objective: microfluidic hydrogel-based logic circuits 3 Stimuli-responsive polymers for microfluidics 3.1 Introduction to hydrogels 3.1.1 Application variety of hydrogels 3.1.2 Hydrogel microstructuring methods 3.2 Theory: stimuli-responsive hydrogels 3.3 PNIPAAm: a multi-responsive hydrogel 4 Design, production and characterization methods of hydrogel-based microfluidic systems 4.1 The semi-automated computer aided design approach for microfluidic systems 4.2 The applied design process 4.3 Fabrication of microfluidic chips 4.3.1 Photoresist master fabrication 4.3.2 Soft lithography for PDMS chip production 4.3.3 Assembling PDMS chips by plasma bonding 4.4 Integration of functional hydrogels in microfluidic chips 4.4.1 Preparation of a monomer solution for hydrogel synthesis 4.4.2 Integration methods 4.5 Effects on hydrogel photopolymerization and the role of integration method 4.5.1 Photopolymerization from monomer solutions: managing the diffusion of free radicals 4.5.2 Hydrogel adhesion and UV light intensity distribution in the polymerization chamber 4.5.3 Hydrogel shrinkage behavior of different adhesion types 4.6 Comparison of the integration methods 4.7 Characterization setups for hydrogel actuators and microfluidic measurements . 71 4.7.1 Optical characterization method to describe swelling behavior 4.7.2 Setup of a microfluidic test stand 4.8 Conclusion: design, production and characterization methods 5 VLSI technology for hydrogel-based microfluidics 5.1 Overview of photolithography methods 5.2 Standard UV photolithography system for microfluidic structures 5.3 Self-made UV lithography system suitable for the mVLSI 5.3.1 Lithography setup for the DFR and SU-8 master exposure 5.3.2 Comparison of mask-based UV induced crosslinking for DFR and SU-8 5.4 Mask-based UV photopolymerization for mVLSI hydrogel patterning 5.4.1 Lithography setup for the photopolymerization of hydrogels 5.4.2 Hydrogel photopolymerization: experiments and results 5.4.3 Troubleshooting: photopolymerization of hydrogels 5.5 Conclusion: mVLSI technologies for hydrogel-based LoCs 6 Components for chemofluidic circuit design 6.1 Passive components in microfluidics 6.1.1 Microfluidic resistor 6.1.2 Planar-passive microfluidic signal mixer 6.1.3 Phase separation: laminar flow signal splitter 6.1.4 Hydrogel-based microfluidic one-directional valves 6.2 Hydrogel-based active components 6.2.1 Reversible hydrogel-based valves 6.2.2 Hydrogel-based variable resistors 6.2.3 CVPT: the microfluidic transistor 6.3 Conclusion: components for chemofluidic circuits 7 Hydrogel-based logic circuits in planar microfluidics 7.1 Development of a planar CVPT logic concept 7.1.1 Challenges of planar microfluidics 7.1.2 Preparatory work and conceptional basis 7.2 The microfluidic CVPT-RTL concept 7.3 The CVPT-RTL NAND gate 7.3.1 Circuit optimization stabilizing the NAND operating mode 7.3.2 Role of laminar flow for the CVPT-RTL concept 7.3.3 Hydrogel-based components for improved switching reliability 7.4 One design fits all: the NOR, AND and OR gate 7.5 Control measures for cascaded systems 7.6 Application scenarios for the CVPT-RTL concept 7.6.1 Use case: automated cell growth system 7.6.2 Use case: chemofluidic converter 7.7 Conclusion: Hydrogel-based logic circuits 8 Summary and outlook 8.1 Scientific achievements 8.2 Summarized recommendations from this work Supplementary information SI.1 Swelling degree of BIS-pNIPAAm gels SI.2 Simulated ray tracing of UV lithography setup by WinLens® SI.3 Determination of the resolution using the intercept theorem SI.4 Microfluidic master mold test structures SI.4.1 Polymer and glass mask comparison SI.4.2 Resolution Siemens star in DFR SI.4.3 Resolution Siemens star in SU-8 SI.4.4 Integration test array 300 μm for DFR and SU-8 SI.4.5 Integration test array 100 μm for SU-8 SI.4.6 Microfluidic structure for different technology parameters SI.5 Microfluidic test setups SI.6 Supplementary information: microfluidic components SI.6.1 Compensation methods for flow stabilization in microfluidic chips SI.6.2 Planar-passive microfluidic signal mixer SI.6.3 Laminar flow signal splitter SI.6.4 Variable fluidic resistors: flow rate characteristics SI.6.5 CVPT flow rate characteristics for high Rout Standard operation procedure

MS FT-2-2 7 Orthogonal polynomials and quadrature: Theory, computation, and applications

Quadrature rules find many applications in science and engineering. Their analysis is a classical area of applied mathematics and continues to attract considerable attention. This seminar brings together speakers with expertise in a large variety of quadrature rules. It is the aim of the seminar to provide an overview of recent developments in the analysis of quadrature rules. The computation of error estimates and novel applications also are described

Generalized averaged Gaussian quadrature and applications

A simple numerical method for constructing the optimal generalized averaged Gaussian quadrature formulas will be presented. These formulas exist in many cases in which real positive GaussKronrod formulas do not exist, and can be used as an adequate alternative in order to estimate the error of a Gaussian rule. We also investigate the conditions under which the optimal averaged Gaussian quadrature formulas and their truncated variants are internal