55 research outputs found

    Analysis of a soft bio-Inspired active actuation model for the design of artificial vocal folds

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    Phonation results from the passively induced oscillation of the vocal folds in the larynx, creating sound waves that are then articulated by the mouth and nose. Patients undergoing laryngectomy have their vocal folds removed and thus must rely on alternative sources of achieving the desired vibration of artificial vocal folds. Existing solutions, such as voice prostheses and the Electrolarynx, are limited by producing sufficient voice quality, for instance. In this paper, we present a mathematical analysis of a physical model of an active vocal fold prosthesis. The inverse dynamical equation of the system will help to understand whether specific types of soft actuators can produce the required force to generate natural phonations. Hence, this is referred to as the active actuation model. We present the analysis to replicate the vowels /a/, /e/, /i/, and /u/ and voice qualities of vocal fry, modal, falsetto, breathy, pressed, and whispery. These characteristics would be required as a first step to design an artificial vocal folds system. Inverse dynamics is used to identify the required forces to change the glottis area and frequencies to achieve sufficient oscillation of artificial vocal folds. Two types of ionic polymer-metal composite (IPMC) actuators are used to assess their ability to produce these forces and the corresponding activation voltages required. The results of our proposed analysis will enable research into the effects of natural phonation and, further, provide the foundational work for the creation of advanced larynx prostheses

    Theoretical and Experimental Investigation on the Multiple Shape Memory Ionic Polymer-Metal Composite Actuator

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    Development of biomimetic actuators has been an essential motivation in the study of smart materials. However, few materials are capable of controlling complex twisting and bending deformations simultaneously or separately using a dynamic control system. The ionic polymer-metal composite (IPMC) is an emerging smart material in actuation and sensing applications, such as biomimetic robotics, advanced medical devices and human affinity applications. Here, we report a Multiple Shape Memory Ionic Polymer-Metal Composite (MSM-IPMC) actuator having multiple-shape memory effect, and is able to perform complex motion by two external inputs, electrical and thermal. Prior to the development of this type of actuator, this capability only could be realized with existing actuator technologies by using multiple actuators or another robotic system. Theoretical and experimental investigation on the MSM-IPMC actuator were performed. To date, the effect of the surface electrode properties change on the actuating of IPMC have not been well studied. To address this problem, we theoretically predict and experimentally investigate the dynamic electro-mechanical response of the IPMC thin-strip actuator. A model of the IPMC actuator is proposed based on the Poisson-Nernst-Planck equations for ion transport and charge dynamics in the polymer membrane, while a physical model for the change of surface resistance of the electrodes of the IPMC due to deformation is also incorporated. By incorporating these two models, a complete, dynamic, physics-based model for IPMC actuators is presented. To verify the model, IPMC samples were prepared and experiments were conducted. The results show that the theoretical model can accurately predict the actuating performance of IPMC actuators over a range of dynamic conditions. Additionally, the charge dynamics inside the polymer during the oscillation of the IPMC are presented. It is also shown that the charge at the boundary mainly affects the induced stress of the IPMC. This study is beneficial for the comprehensive understanding of the surface electrode effect on the performance of IPMC actuators. In our study, we introduce a soft MSM-IPMC actuator having multiple degrees-of-freedom that demonstrates high maneuverability when controlled by two external inputs, electrical and thermal. These multiple inputs allow for complex motions that are routine in nature, but that would be otherwise difficult to obtain with a single actuator. To the best of our knowledge, this MSM-IPMC actuator is the first solitary actuator capable of multiple-input control and the resulting deformability and maneuverability. The shape memory properties of MSM-IPMC were theoretically and experimentally studied. We presented the multiple shape memory properties of Nafion cylinder. A physics based model of the IPMC was proposed. The free energy density theory was utilized to analyze the shape properties of the IPMC. To verify the model, IPMC samples with the Nafion as the base membrane was prepared and experiments were conducted. Simulation of the model was performed and the results were compared with the experimental data. It was successfully demonstrated that the theoretical model can well explain the shape memory properties of the IPMC. The results showed that the reheat glass transition temperature of the IPMC is lower than the programming temperature. It was also found that the back-relaxation of the IPMC decreases as the programming temperature increases. This study may be useful for the better understanding of the shape memory effect of IPMC. Furthermore, we theoretically modeled and experimentally investigated the multiple shape memory effect of MSM-IPMC. We proposed a new physical principle to explain the shape memory behavior. A theoretical model of the multiple shape memory effect of MSM-IPMC was developed. Based on our previous study on the electro-mechanical actuation effect of IPMC, we proposed a comprehensive physics-based model of MSM-IPMC which couples the actuation effect and the multiple shape memory effect. It is the first model that includes these two actuation effects and multiple shape memory effect. Simulation of the model was performed using finite element method. To verify the model, an MSM-IPMC sample was prepared. Experimental tests of MSM-IPMC were conducted. By comparing the simulation results and the experimental results, both results have a good agreement. The multiple shape memory effect and reversibility of three different polymers, namely the Nafion, Aquivion and GEFC with three different ions, which are the hydrogen, lithium and sodium, were also quantitatively tested respectively. Based on the results, it is shown that all the polymers have good multiple shape memory effect and reversibility. The ions have an influence on the broad glass transition range of the polymers. The current study is beneficial for the better understanding of the underlying physics of MSM-IPMC. A biomimetic underwater robot, that was actuated by the MSM-IPMC, was developed. The design of the robot was inspired by the pectoral fish swimming modes, such as stingrays, knifefish and cuttefish. The robot was actuated by two soft fins which were consisted of multiple IPMC samples. Through actuating the IPMCs separately, traveling wave was generated on the soft fin. Experiments were performed for the test of the robot. The deformation and the blocking force of the IPMCs on the fin were measured. A force measurement system in a flow channel was implemented. The thrust force of the robot under different frequencies and traveling wave numbers were recorded. Multiple shape memory effect was performed on the robot. The robot was capable of changing its swimming modes from Gymnotiform to Mobuliform, which has high deformability, maneuverability and agility

    3D-printing technology applied to the development of bio-inspired functional acoustic systems

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    Examples of bio-inspired technology can be found almost everywhere in society: robots with specific capabilities, materials with unique physical and chemical properties, aerodynamic systems, and architectonic structures are a few examples of taking profit of evolution-driven processes to solve common engineering problems. One field of research taking advantage of bio-inspiration is that of acoustical engineering, aiming to find solutions to problems arising from the miniaturisation of microphones and loudspeakers. Studying the auditory organs of insects to seek inspiration for new design structures is one of the best ways to solve such an important problem. Another discipline of science that has experienced a research boom is that of materials science, as development of new materials has attracted the attention of researchers. In addition, three-dimensional (3D) printers have contributed to further development in materials science making the production process more efficient. The aim of this research is to bring these fields of science together to develop novel bioinspired, polymer-based sensors presenting functional specific acoustic properties after 3D-printing. While the study of complex biological hearing systems provides inspiration to develop sensors featuring specific properties, the use of polymer-based materials allows the customization of the manufacturing process, as the produced parts adapt to the desired needs. In this thesis one such insect auditory system that has been thoroughly studied is that of the desert locust Schistocerca gregaria as it presents a simple structure that allows for acoustic frequency selectivity and displays nonlinear acoustic phenomena. Prior to the development of a bio-inspired system, a mathematical description of the mechanical response of such a structure is presented. Furthermore, the physical behaviours measured on the locust tympanal membrane have been studied using finite element analysis. The 3D-printed functional sensors have been used to determine the degree of accuracy between experimental and theoretical results.Examples of bio-inspired technology can be found almost everywhere in society: robots with specific capabilities, materials with unique physical and chemical properties, aerodynamic systems, and architectonic structures are a few examples of taking profit of evolution-driven processes to solve common engineering problems. One field of research taking advantage of bio-inspiration is that of acoustical engineering, aiming to find solutions to problems arising from the miniaturisation of microphones and loudspeakers. Studying the auditory organs of insects to seek inspiration for new design structures is one of the best ways to solve such an important problem. Another discipline of science that has experienced a research boom is that of materials science, as development of new materials has attracted the attention of researchers. In addition, three-dimensional (3D) printers have contributed to further development in materials science making the production process more efficient. The aim of this research is to bring these fields of science together to develop novel bioinspired, polymer-based sensors presenting functional specific acoustic properties after 3D-printing. While the study of complex biological hearing systems provides inspiration to develop sensors featuring specific properties, the use of polymer-based materials allows the customization of the manufacturing process, as the produced parts adapt to the desired needs. In this thesis one such insect auditory system that has been thoroughly studied is that of the desert locust Schistocerca gregaria as it presents a simple structure that allows for acoustic frequency selectivity and displays nonlinear acoustic phenomena. Prior to the development of a bio-inspired system, a mathematical description of the mechanical response of such a structure is presented. Furthermore, the physical behaviours measured on the locust tympanal membrane have been studied using finite element analysis. The 3D-printed functional sensors have been used to determine the degree of accuracy between experimental and theoretical results

    3D printing assisted development of bioinspired structure and device for advanced engineering

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    Smart materials with bio-inspired structure and stimuli responsive features can sense the external and internal condition changes, such as temperature, light intensity, pH or ion concentration. Those unique functions have been widely utilized in cutting edge engineering applications, such as flexible sensors, soft robotics and tissue engineering. Meanwhile, conventional manufacturing methods such as moulding, and lithography-based microfabrication still represent the mainstream force in scale up manufacturing. Considerable limitations for these technologies, such as on demand rapid prototyping, the high cost and low-volume production, remain to be overcome. In this PhD project, I explored the advanced manufacturing in facilitating the complex structure, with higher controllability, lower prototyping cost and extended applications (flexible sensors, soft robots, biomedical devices, etc.). The key practice is to utilize the high resolution 3D printing technology to create dedicated bio inspired structures based on functional materials. Combined with advanced micro/nano engineering, we have achieved a variety of techniques/prototypes for future applications, such as optical control, micro-fluidic and bio-medical systems, etc

    Hiding the squid:patterns in artificial cephalopod skin

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    Cephalopods employ their chromomorphic skins for rapid and versatile active camouflage and signalling effects. This is achieved using dense networks of pigmented, muscle-driven chromatophore cells which are neurally stimulated to actuate and affect local skin colouring. This allows cephalopods to adopt numerous dynamic and complex skin patterns, most commonly used to blend into the environment or to communicate with other animals. Our ultimate goal is to create an artificial skin that can mimic such pattern generation techniques, and that could produce a host of novel and compliant devices such as cloaking suits and dynamic illuminated clothing. This paper presents the design, mathematical modelling and analysis of a dynamic biomimetic pattern generation system using bioinspired artificial chromatophores. The artificial skin is made from electroactive dielectric elastomer: a soft, planar-actuating smart material that we show can be effective at mimicking the actuation of biological chromatophores. The proposed system achieves dynamic pattern generation by imposing simple local rules into the artificial chromatophore cells so that they can sense their surroundings in order to manipulate their actuation. By modelling sets of artificial chromatophores in linear arrays of cells, we explore the capability of the system to generate a variety of dynamic pattern types. We show that it is possible to mimic patterning seen in cephalopods, such as the passing cloud display, and other complex dynamic patterning

    Thermo-Mechanical Modeling and the Application of Coiled Polymer Actuators in Soft Robotics and Biomimetics

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    Coiled polymer actuators (CPA) are a recently discovered smart material. Due to their large tensile stoke and power densities they are often used as actuators or artificial muscles. CPA’s are fabricated from a polymer fiber, typically nylon, mechanically twisted into a coil or coiled around a mandrel and annealed. When heated over the glass transition temperature they can contract, expand or exhibit torsional actuation, depending on the fabrication method and end conditions. The fabrication and application of CPA is well documented and has made many innovations in the fields of smart materials, soft robotics and the likes. However, there is a lack of knowledge in the modeling of CPA, this is partly due to the novelty of the actuator. To address this problem, a theoretical and experimental investigation of thermo-mechanical response is proposed. An energy and variational methods and continuum mechanics approach is utilized with numerical methods to describe the actuation response. To verify the model, the numerical simulation displacement response is compared to CPA samples that are fabricated and experimentally tested in lab using a dynamic machine analyzer (DMA). The results indicate the proposed model accurately predict the actuation response of the CPA under thermal loading. The numerical simulation and experimental comparison is in good agreement and helps to further understand the underlining cause of the actuation behavior of the coiled polymer actuator. Furthermore, the model can be used in application purposes where the results of the model can be used in designing and optimizing soft robotics using CPA as an artificial muscle. In addition to the numerical and experimental investigation of the CPA’s thermomechanical response, an application in biomimetics is being studied. Biomimetics is an interdisciplinary field in engineering and sciences used to overcoming complex human challenges by designing and fabricating materials and systems modeled after nature. Applications of biomimicry can be seen in many technological advancements such as catheters, hearing devices, and artificial appendages such as arms, legs and fingers. The inspiration for this study is the hydrofoil like structured pectoral fin of the Harbor Porpoise whale. Studies will be focused on understanding the fluid forces acting on the pectoral fin. First and foremost, a highly accurate pectoral fin is fabricated from CT scans of a Harbor Porpoise whale fin. 3D models are obtained using Simpleware ScanIP and post-processed in Autodesk for 3D printing components, which were used to assemble to artificial whale fin. An array of thermally driven Coiled Polymer Actuators (CPA) fabricated from Nylon and heated with Nichrome are used as artificial muscles for actuating the pectoral fin. CPA’s were used for their similarity to biological muscles and are of great interest due to its high specific power and large actuation stroke. A simple control circuit for supplying power to the Nichrome heating wires is developed using an Arduino and motor drivers. The displacement over time of the fin is tested and captured using a laser distant sensor. The fin shows a great displacement response, largely deflecting in both direction relative to its size. The artificial fin was then be further utilized in our studies. The fluid forces imposed on the fin while in motion was measured in a laboratorycontrolled setting. A low-velocity belt driven tow tank was used to displace the artificial fin through water. The tow velocity was varied, and the drag force measurements were taken with and without fin actuation using a cantilever beam load cell. A theoretical derived drag force was compared to the experimental drag data and showed good comparison for the non-actuated fin. Increased drag was exhibited with actuation in both directions when towed through water. This demonstrates the ability of the fin to manipulate is geometry to change the drag force on itself serving as a controllable hydrofoil. We hope to elaborate on this ability and apply it to mechanical designs such as under and above water vehicles

    A Hyperelastic Porous Media Framework for Ionic Polymer-Metal Composites and Characterization of Transduction Phenomena via Dimensional Analysis and Nonlinear Regression

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    Ionic polymer-metal composites (IPMC) are smart materials that exhibit large deformation in response to small applied voltages, and conversely generate detectable electrical signals in response to mechanical deformations. The study of IPMC materials is a rich field of research, and an interesting intersection of material science, electrochemistry, continuum mechanics, and thermodynamics. Due to their electromechanical and mechanoelectrical transduction capabilities, IPMCs find many applications in robotics, soft robotics, artificial muscles, and biomimetics. This study aims to investigate the dominating physical phenomena that underly the actuation and sensing behavior of IPMC materials. This analysis is made possible by developing a new, hyperelastic porous media modeling framework for IPMCs. Using the principles of continuum thermodynamics and multiphasic materials, a finite-strain porous media formulation of IPMC materials is developed. The intricate polymer-electrode interface coupling is extended to such a finite-strain model by accounting for charge conservation at deforming material interfaces. Using this new modeling framework, the effects of kinematic nonlinearity are explored, and a partially linearized kinematic model is proposed for capturing rotational deformation in an otherwise linear model. The most comprehensive dimensional analysis of IPMC transduction phenomena is presented, characterizing the IPMC actuator, short-circuit current, and open-circuit voltage response under static and dynamic loading. The information obtained in this analysis is used to construct nonlinear regression models for the transduction response as univariant and multivariant functions. Automatic differentiation techniques are leveraged to linearize the nonlinear regression models in the vicinity of a representative IPMC description and derive the sensitivity of the transduction response with respect to the driving independent variables. Further, the multiphysics model is validated using experimental data collected for the dynamic IPMC actuator and voltage sensor. With data collected from physical samples of IPMC materials in-lab, the regression models developed under the new computational framework are verified. Using these regression models to interpret the experimental data allowed for further material property characterization to occur, demonstrating the capability of using hybrid computational / experimental regression models to extract information regarding material properties that would otherwise be unknown within the data collected. Key values for the mobile concentration and electric potential fields are approximated using order-of-magnitude arguments and the sharpness of the gradients that occur at the polymer-electrode interfaces of IPMC materials. These values allow for approximate reconstruction of the fields themselves, which in turn are leveraged to formulate the internal bending moments and steady-state curvature of the IPMC. Using both an Euler-Bernoulli beam and a constant curvature arc model for the IPMC, the deformation and rotation of the of the order of magnitude model demonstrated impressive performance for being based on rough approximations. The curled shape of IPMCs under large applied potentials with nonlinear deformation are recovered using this simplified model, and the ability to extend the model for dynamic actuation is outlined

    Centrifugal assembly of bijel ropes via helical microfluidics

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    Bicontinuous interfacially jammed emulsion gels (bijels) are soft materials that retain a liquid bicontinuous network stabilized by an interfacially jammed layer of nanoparticles. In this thesis, we investigated a microfluidic twisting method to fabricate micro-ropes of nano-structured bijel fibers. This method shows how weak microfibers with tensile strengths of a few kPa can be reinforced by 4 orders of magnitude by means of microfluidic twisting. Microfluidic twisting allows to produce continuous bijel fiber ropes of controllable architecture. Modelling the fluid flow field reveals the rope geometry dependence on a subtle force balance composed of rotational and translational shear stresses. However, the direction of the centrifugal force determines whether microropes undergo undulation during microfluidic twisting. The undulation of ropes can be avoided by decreasing the density of the fiber casting mixture, or upon increasing the density of the co-flowing liquid, enabling a controlled and continuous collection of uniform microropes. We envision microfluidic twisting to enable the fabrication of new composite materials with applications in flexible electronics, micro robotics, actuators, and tissue engineering. Furthermore, the knowledge gained from this thesis will facilitate future studies of microfiber twisting, as well as the assembly of particles, emulsion droplets or biological cells via microfluidic twisting
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