Going beyond naturally occurring materials, Metamaterials exploit a design at the microscale resulting in macroscopic behaviour, to achieve different or even new properties that can have a wide range of applications. By incorporating sensors, actuators and control, Robotic Metamaterials can achieve even more extremely different behaviour such as odd elasticity. By using local control and non-reciprocal couplings between actuators, an asymmetric elastic response can be achieved. Due to the non-conservative nature of this coupling, the system has a tendency to cycle and give rise to complex behaviours such as locomotion. Through simple and localized control, complex material behaviour is achieved, where the body is performing the computation and no complex control or computations systems are required. In this work, a new unit cell for a metamaterial that achieves this odd elasticity is designed, manufactured, and finally tested. The unit cell consists of 3 hexagonal mechanisms with compliant joints and a linear actuator inside and is locally controlled. By using a novel Actuator design and engineering principles such as compliant mechanisms, a unit cell design is achieved that has 10 times smaller scale per area and 15 times higher strength-to-weight ratio compared to existing work. Finally, this unit cell was characterized and combined into a larger lattice showcasing the possibilities for future research into the behaviour of odd elastic metamaterials.

In up to 39% of reduced distal radius fractures, re-displacement of the fracture occurs in the cast. In most cases, the cast becomes too loose as soft tissue swelling decreases over time and the cast no longer provides sufficient support to keep the fracture reduced. This issue could be addressed by introducing a smart memory cast, a cast that would employ soft polymer foam to relieve stress concentration while providing the required support stiffness to maintain the reduction throughout the whole cast treatment period. Soft polymer foams are characterised by a plateau phase in which the pressure does not increase as the material is compressed. The concept is tested by placing a soft polyurethane foam between an artificial arm that mimics soft tissue swelling and a synthetic cast. The pressure in the smart memory cast is measured by thin film pressure sensors. The average pressure in the smart memory cast was 15.4 mmHg and was reduced by 47.8% compared to the average pressure measured, 29.5 mmHg, in a traditional cast. The pressure in the smart memory cast remained under 25.0 mmHg which was set as a threshold value that could lead to a compartment syndrome. In contrast with the traditional cast where the pressure kept increasing above the threshold value as the artificial arm kept swelling, in the smart memory cast the pressure plateaued. The results from this study show that by introducing a filler material with non-linear elastic properties in a synthetic cast, the pressure concentration is reduced compared to a traditional cast and the pressure plateaus as soft tissue swelling increases.

Vibrations and disturbances are becoming more of a concern as lightweight, flexible structures in high-tech systems are pushed towards faster speeds and higher precision. Active Vibration Control (AVC) methods have been effectively used to attenuate vibrations and increase the bandwidth of these systems. With the miniaturisation of electronics, an increasing amount of sensor and actuator pairs can be used for AVC applications. Not only does this allow for higher active damping, it also grants more flexibility in terms of control. This trend has led to the study of robotic metamaterials and meta-structures: large-scale engineered materials build out of a repeating pattern of unit cells, where each unit cell contains a sensor, actuator and sometimes even a computing unit. The optimal control architecture to use for these systems is a difficult dilemma, since decentralised and centralised control schemes both have fundamental trade-offs in terms of performance and scalability. In this paper we study distributed control, a promising middle-ground solution that is hardly used in AVC applications. We show with the use of LQR that a distributed control architecture can achieve optimal performance in the low-frequency range for robotic materials with relative measurements. Additionally, the actuators use lower maximum control forces and a distributed control architecture remains scalable for implementation in large-scale systems. In this paper the robotic cantilever beam is studied as a specific example as it represent many typical high-tech applications. Furthermore, implications on periodic robotic meta-structures are made using LQR in the Spatial Fourier Domain.

In the field of vibration energy harvesting, vibration energy is tranduced to electrical energy to power small, low powered devices. Many energy harvesters are produced in the form of a resonator, where resonant amplification enables efficient operation of the energy harvester. At low frequencies below 10 hz, input motions quickly increase for a constant input acceleration and resonant amplification results in energy harvesters that are too large to implement them. A solution is sought in creating a nonresonant energy harvester. The stiffness of a strongly coupled piezoelectric beam is compensated by adding negative stiffness to bring it to a near statically balanced state. This negative stiffness is embodied by attracting magnets. To model the dynamics and voltage output of the harvester, a modal analysis based distributed parameter model is used and further developed by including negative stiffness and force-displacement measurements of the stiffness compensated piezo. To investigate the mechanical behaviour of a compensated piezo, force-displacement measurements are carried out at different deformation speeds and load resistances. From these measurements, it has been observed that the stiffness of the compensated piezo strongly depends on the connected load resistance and the deformation speed. Furthermore, memory effects in piezoelectric hysteresis found in actuators such as curve alignment and wipeout have also been confirmed in force-displacement measurements. The performance of the harvester has been evaluated by exciting it on a linear air bearing stage. It has been found that for excitations between 2 and 6 hz, the error in RMS power between simulation and measurement remains below 10%. For its range of excitation, this harvester has been observed to be the most efficient with respect to prior art from literature. Therefore, stiffness compensation of a piezoelectric energy harvester can be considered as a successful method to improve the efficiency at low frequency excitation.

Achieving appropriate soft tissue tension around the hip joint is an important factor for achieving hip stability after Total Hip Arthroplasty (THA). Hip instability leads to dislocations, pain, and is a common reason for early revision surgery. The current soft tissue tension assessments available during surgery rely on experience, and dislocations occur twice as often after THAs performed by inexperienced surgeons compared to more experienced surgeons. This paper presents a new mechanism which measures and displays hip force in Three Degrees Of Freedom (3-DOF) during THA. A prototype measured axial and normal force components up to 75 N with a sampling frequency of 14.6 Hz, an accuracy up to 11 N, and a Root Mean Square Error (RMSE) of 4.0 N (axial) and 3.0 N (normal). Additionally, it measured the normal force direction with an accuracy up to 7.1∙10^(-2) π rad and RMSE of 7.1∙10^(-2) π rad. Data needs to be collected to build a predictive model which estimates the required hip force range and distribution to achieve a stable joint. When combined with such a predictive model, the proposed design is a promising assistive surgical tool.

Future consumer products, medical devices and manufacturing processes can benefit from systems with a high number and a high density of individually controlled actuators that are flexible and use little energy, materials and space. These systems with a high count and high density of actuators can be addressed as distributed actuation systems. In nature these distributed actuation systems are already present in the form of organs, eukaryotic cells or body parts such as an elephant’s trunk. This kind of system could be useful for handling fragile materials, delivering drugs inside the human body or creating replacement organs. Creating distributed mechatronic systems using conventional components is difficult, as the rigid parts often lead to complex constructions. This thesis presents a new paradigm for distributed actuation systems: combining planar bending smart materials with the Japanese art of Kirigami. This is demonstrated with the creation of a novel actuator design and modelling approach.First a literature study is presented on methods that have been used to actuate Origami and Kirigami (O&K) structures. General information is provided on several smart materials that can be used for this purpose. The reported methods and materials are evaluated on their potential for distributed actuation. The literature shows that electro-mechanical smart materials can be used for the design of distributed actuator systems. It is shown that multiple, scalable actuators can be designed in one sheet and can be actuated locally. Literature reveals preliminary research on cutting soft electro-active polymer (EAP) Kirigami structures. These EAPs are suitable for the creation of multi-DOF, distributed actuators using O&K techniques. However, this far the investigation addresses only cm-sized structures that exhibit a bending behaviour and the potential of the O&K techniques on EAPs have not been studied. The second study investigates the concept of utilizing Kirigami techniques on ionic polymer metal composite (IPMC) materials to manufacture distributed actuators. Different cm-sized designs are described and realized that produce a large strain linear motion from the bending motion of IPMCs. The designs are experimentally validated. The results demonstrate that it is possible to etch and cut a multitude of actuation units into planar bending smart material transducers and that bending actuation can be used to realize translation.To facilitate design and optimization of these IPMC Kirigami structures, a model is needed that predicts the electro-mechanical behaviour and is easy to implement. Existing models are not suitable as they will result in complex and elaborate model constructions when more advanced structures have to be implemented. This thesis presents a practical electrical model in Comsol Multiphysics. The electrical parameters of an IPMC beam are identified. Identified properties include the surface conductivity, through material conductivity and permittivity. The electrical models are validated by comparing the simulations with a time-domain experiment with a sinusoidal input signal of 1V at 1Hz. The results show that the models can be used to describe the macroscopic electrical behavior and can be further used in analysing more complex structures ones the mechanical part of the Comsol model is also completed.

A new radical design approach arose from the need to develop a bipolar electrosurgical instrument that is modular and cleanable, thus reusable and therefore suitable for low- and middle-income countries (LMICs). Advanced Bipolar Vessel Sealer (BVS) instruments that are currently on the market cannot be cleaned or maintained well and are therefore most often sold as disposables. Especially in LMICs it is a significant financial burden for hospitals. This possibly leads to the re-use of single-use intended instruments which in turn jeopardizes patient safety. Simultaneously, designing a reusable instrument fits well in the transition to a more circular and sustainable society. To perform advanced laparoscopic surgery with cleanable and affordable electrosurgical instruments, a new design approach is needed. A first phase was initiated by the creation of a cable less steering principle called Shaft Actuated Tip Articulation (SATA) mechanism [6]. Unfortunately, by adding electrically conductive wires to a SATA instrument it loses its modularity and thus cleanability, precisely for which the SATA technology offered a solution in the first place. In addition, there are no non-robotically controlled and reusable BVS instruments with two DOFs available on the market. By being steerable, the user of the instrument is able to deliver a higher quality seal as well as to seal more difficult-to-reach blood vessels and tissue. In this thesis project the goal is to redesign a SATA instrument which sustains bipolar vessel sealing and thus designing a BVS that is easy to clean, easily disinfected and sterilized and which is reusable for a vast amount of surgical procedures. Ideas have been gained by analysing the SATA mechanism and studying commonly used BVS devices. A systematic selection procedure based on the design requirements has resulted in a winning concept for the conduction of electricity through the SATA instrument. For the design of the tip, determining factors were elaborated on, including the construction of the open and close mechanism and the force transmission ratio between the required seal force on the blood vessel or tissue and the necessary tensile force in the core of the instrument. The most critical components of the final model have been identified and evaluated by means of FEM simulations and an experiment. The FEM simulations of the tip components show that the design is satisfactory and that a safety factor of ~1.5 has been achieved. This means that these components do not fail due to normal use and they have a long lifespan as well. In the experiment a flexible nitinol guidewire with Teflon coating was tested for wear by pulling the guidewire through an angled SATA hinge. After some necessary adjustments and additions to the design of the BVS, the results were improved but not optimal. The outcome of this project is a good basis for the BVS design where the steerability has been maintained as well as the modularity and cleanability. The reusability depending on the flexible coating around the core needs to be further investigated and improved.

This thesis is centred around the problem that heart failures become more common when other dis-eases could be treated better. Although surgery could fix the immediate effects of heart failures, therecovery after the surgery is hindered by the heart not being able to pump enough blood. There aresolutions available but they are not implemented due doing more harm then good to the heart. Thisthesis will look into a way to aid the recovering heart by applying a compressional force to the outsideof the heart. Previous attempts on fixing this problem could not follow the motion of the heart closeenough due to the lack of actuation resolution, i.e. the local differentiation of the actuation applied tothe heart. This caused damage to the heart muscle, which in the end causes death due to too littleblood flow.Due to lack of actuation resolution of the previous solutions, the focus of this thesis will be on the dis-tribution of the actuation and not the actuation to the heart itself. A baseline for the requirements wasneeded to make an informed decision about the different solutions to distribute the actuation. This wasdone using a MatLab script. This gave the actuation characteristics of a compression of 20 percent witha pressure of 20 [kPa] when a compression jacket of 5 [mm] thickness around the heart is used. Therelative high compression together with the pressure directed the solution for such an actuator towardsfluids.Common fluid actuators that would have a high local differentiation in actuation require lots of pumpsor lots of valves, both of these options have as a downside that they take up to much space. That iswhere smart fluids have an advantage by decreasing the size of a pump or a valve by including thefluid in the active volume. Two of these smart fluids that seem promising are; Ferrofluids and magnetorheological fluids. Ferrofluids are activated by a magnetic field and will cause a change in internalpressure similar to how gravity affects internal pressure in a fluid. The only difference is that it couldbe about four to five orders of magnitude stronger over small distances of about a tenth of a millimetre.The magneto rheological fluid changes its viscosity in the direction perpendicular to the magnetic fieldwith the change being related to the strength of the applied field.The thesis will discuss the use of Ferrofluids as an active fluid in a pump, and magneto rheologicalfluids, MRF, as the active fluid in a valve. Ferrofluids are not feasible to be used as individual unitsas they barely meet the requirements of 20 [kPa] of pressure with the flow rate needed to actuate thejacket, without taking the fluidic losses of such a jacket into account. Whereas the MRF based valvecould achieve a pressure difference of 20 [kPa] over the valve, without being of the limits of the op-erational value of the fluid. This is enough to have both a fully opened valve and a closed one usingthe pressure needed from the requirements. Therefor the thesis recommends the further research intoimplementing a full actuation system for a heart assist device using valves based on MRF.

In this MSc thesis report, the process of developing a laser aiming solution for the purpose of bird repelling will be described. This process consists roughly of five phases: Setting up requirements, generating concepts, picking and developing a single concept, building and finally testing this concept. The current laser aiming solution is not satisfactory for many applications where safety is critical. The laser technology used by Bird Control Group to repel the birds can be dangerous to the human eye under certain circumstances. Therefore, a more accurate aiming solution is required. A concept where the source is stationary and the laser beam is reflected with a mirror is chosen over a moving source configuration, as the moving mass in that configuration is much lower (around 4% of the moving source configuration). This means the system can reach much higher speeds and react to higher frequency input signals due to the higher eigenfrequencies of the system. The completed prototype proved to be two orders of magnitude more accurate than the current solution, while also being much faster when required. Both of these factors and other factors contributed to the success of this project.

To achieve high motion accuracy and repeatability for a variable reluctance tunable magnet actuator that uses linear controllers, this article proposes a novel actuator design that has a linearized force-flux relation. Prior designed variable reluctance tunable magnet actuators use a C-shaped actuator that has a quadratic relation between the force and the flux. By using lumped parameter models, an Hybrid Tunable Magnet Actuator design based on biased fluxes is developed. The linear behaviour of this design is proven by a finite element analysis. The force-flux relation is piecewise linear for different positions depending on the direction of the flux. Within a position range of ± 500 µm and a force range of ± 20 N, the error of a linear fit is in the order of 0.08 N. With an experimental setup the linear relation is also proven with an error of 0.03 N. Comparing the designed tunable magnet actuator with an hybrid reluctance actuator shows that the tunable magnet actuator is more efficient for quasi-static forces that are constant for time periods longer than 1.4 s.

Malaria remains a major burden on global health, with roughly 200 million reported cases worldwide and more than 400,000 deaths per year. According to the World Health Organization, ninety-three percent of all deaths due to the disease occurred in developing countries in sub-Saharan Africa. This large percentage is directly correlated to the lack of diagnostic tools in those developing countries. Early and accurate diagnosis of malaria is a critical aspect of efforts to control the disease. Microscopic examination of a blood smear remains the clinical gold standard for malaria diagnosis. However, this examination is subjective and requires a highly experienced and skilled microscopist. Next to that, it is a labor-intensive procedure that is very time-consuming. Automated hematology analyzers that are currently available are of high cost and therefore only suitable for laboratories and not for a local doctor’s practice. The objective of this research was to provide the design of a compact and affordable compliant XY positioning stage that can be integrated into a microscope to be used for automated malaria diagnosis in developing countries without the involvement of a laboratory. The challenge imposed with this objective is that compliant stages can only reach small strokes due to the inherent imperfection of flexures. Achieving long-stroke results in high stresses and cross-axis coupling between the two motion axes which is undesired. This challenge is solved by implementing a constraint-based method that results in a design with parallel kinematics and modular structure that exhibits high geometric decoupling. A demonstrator of the precision stage is 3D-printed out of PLA and used for performance evaluation measurements. The demonstrator managed to achieve the set requirements for blood smear analysis. Therefore, it can be concluded that the stage was designed successfully and it can be implemented for automated malaria diagnosis to help Africa control the disease.

Multi­-material 3D inkjet printing has great potential for rapid prototyping and manufacturing of functional mesoscale structures when novel inks are combined into a fully integrated AM-process. This process can be faster and cheaper than conventional methods to produce functional structures. Research is conducted on a large range of potentially inkjet­-printable materials to extend current possibilities with 3D inkjet printing. Material incompatibility together with strict fluid properties limit the range of multifunctional inks available for an integrated print process. This raises challenges such as printing with three or more materials, and finding inkjet printable materials that can be cured simultaneously using the same curing method. The aim of this research is to print functional structures using at least three materials consisting of a structural, support, and conductive material, requiring only one curing technique involving UV light exposure. An experimental setup of PiXDRO LP50 inkjet printers and various printhead assemblies are used to conduct experiments. Suitable off the shelf available inks are selected after a state of the art literature review. Stratasys Vero­series and Stratasys SUP706B are industry standard, compatible materials and cure using UV induced photopolymerisation. They are chosen as structural and support material, respectively. Novacentrix Metalon JS­B25P and Mitsubishi NBSIJ­MU01 silver nanoparticle inks are chosen as conductive inks. First, multi­material printing is set up and extended to 3D printing using the structural and support material inks only. Afterwards, conductive inks are tested for resistivity and behaviour on different substrates before integrating with the structural and support material ink into a multi­material 3D print. Conductive nanoparticle inks show good conductivity on photopaper substrate, but not when printed on top of structural material. Several experiments are performed to document ink behaviour and optimise performance. A workflow is designed allowing the conversion of complex CAD models to inkjet ­printable files. Custom support material density for stronger supports can be generated using an in-­house developed conversion application. Proof­ of ­concept multi­-material functional structures are printed showcasing success of the proposed methodology.

Inkjet printing is a technology that has been widely studied and implemented. The liquids that are used for inkjet printing can vary. There is the traditional ink which can be found in almost every household printer. But it is also possible to use inkjet printing to deposit drugs, proteins and nanoparticles on substrates. Inkjet printing has the ability to precisely deposit picoliters of liquid onto the substrate. Thus, reducing cost and waste when the material being used is expensive and/or of limited quantity. This project works with a LP50 PIXDRO inkjet printer. Another interest that gained traction in the scientific community are the stimuli-responsive microgels. These microgels are able to change their dimensions depending on the external stimuli and if this stimuli is removed from the microgel, it changes back to its original shape, thus it is a reversible process. This project uses a suspension of the stimuli-responsive microgel; poly(N-isopropylacrylamide)-coacrylic acid (pNIPAm). This microgel is responsive to temperature and pH. To deposit the pNIPAm suspension on the substrate, inkjet technology will be used. The printability of the pNIPAm will be determined by characterizing the physical and rheological properties. Such as the density, surface tension, viscosity and particle size of the pNIPAm beads. These properties will be compared to the ideal liquid requirements given by the print cartridge that will be used, a Fuijifilm Dimatix. To influence the surface tension three surfactants will be tested. These surfactants are Triton X-114 (TRT), Sodium dodecyl sulphate (SDS) and Hexadecyltrimethylammonium bromide (CTAB). Based on the results the and comparison to the requirements the surfactant Triton X-114 is chosen because it lowers the surface tension the most. While it has minimal to no affect on the pNIPAm particles. The next phase of the project is testing the printability of the pNIPAm. This is done by adjusting the waveform on the LP50 PIXDRO inkjet printer. As a result it is indeed possible to deposit pNIPAm on a substrate with an inkjet printer. After this step a SEM is used to investigate if the printed pNIPAm particles will form a monolithic layer. This monolithic layer is important when it comes to having a functional etalon. The pNIPAm particles form indeed a monolithic layer on the substrate. The last step is to see if there is a peak shift in the wavelength when the temperature is increased. The microgel based etalons that used an inkjet printer to deposit the micrgol show a peak shift. Therefore, it can be concluded that it is possible to use an inkjet printer to deposit pNIPAm on a substrate and that the pNIPAm particles behave according to literature. All the results of this project show that using an inkjet printer is a viable alternative for fabricating microgel based etalons.

Inkjet printing is a technology that has been widely studied and implemented. The liquids that are used for inkjet printing can vary. There is the traditional ink which can be found in almost every household printer. But it is also possible to use inkjet printing to deposit drugs, proteins and nanoparticles on substrates. Inkjet printing has the ability to precisely deposit picoliters of liquid onto the substrate. Thus, reducing cost and waste when the material being used is expensive and/or of limited quantity. This project works with a LP50 PIXDRO inkjet printer. Another interest that gained traction in the scientific community are the stimuli-responsive microgels. These microgels are able to change their dimensions depending on the external stimuli and if this stimuli is removed from the microgel, it changes back to its original shape, thus it is a reversible process. This project uses a suspension of the stimuli-responsive microgel; poly(N-isopropylacrylamide)-coacrylic acid (pNIPAm). This microgel is responsive to temperature and pH. To deposit the pNIPAm suspension on the substrate, inkjet technology will be used. The printability of the pNIPAm will be determined by characterizing the physical and rheological properties. Such as the density, surface tension, viscosity and particle size of the pNIPAm beads. These properties will be compared to the ideal liquid requirements given by the print cartridge that will be used, a Fuijifilm Dimatix. To influence the surface tension three surfactants will be tested. These surfactants are Triton X-114 (TRT), Sodium dodecyl sulphate (SDS) and Hexadecyltrimethylammonium bromide (CTAB). Based on the results the and comparison to the requirements the surfactant Triton X-114 is chosen because it lowers the surface tension the most. While it has minimal to no affect on the pNIPAm particles. The next phase of the project is testing the printability of the pNIPAm. This is done by adjusting the waveform on the LP50 PIXDRO inkjet printer. As a result it is indeed possible to deposit pNIPAm on a substrate with an inkjet printer. After this step a SEM is used to investigate if the printed pNIPAm particles will form a monolithic layer. This monolithic layer is important when it comes to having a functional etalon. The pNIPAm particles form indeed a monolithic layer on the substrate. The last step is to see if there is a peak shift in the wavelength when the temperature is increased. The microgel based etalons that used an inkjet printer to deposit the micrgol show a peak shift. Therefore, it can be concluded that it is possible to use an inkjet printer to deposit pNIPAm on a substrate and that the pNIPAm particles behave according to literature. All the results of this project show that using an inkjet printer is a viable alternative for fabricating microgel based etalons.

Shape changing active metamaterial could form the structural backbone of an object as well as deliver the actuation. The integration of these two functions saves design space and allows for creative topologies. The literature study of this thesis investigated smart material actuator solutions that could be used to enable such active metamaterials, covering PVDF, dielectric elastomers, IPMC, conducting polymer, carbon nanotubes and piezoelectric ceramics. It is found that dielectric elastomers achieve high strains, low stress and need high driving voltages. Conducting polymers are able to deliver both high stress and high strain, but consume relatively much power. If power consumption is a priority, Electronic EAPs are preferred. PVDF does not excel on stress or strain, but is an overall good performer. The outlook of realizing active metamaterials via integration of actuation paves the way for non-rigid body deformations and broadens the view on potential applications. At the moment such a system cannot be realized due to the lack of appropriate designs and manufacturing methods. The objectives of this report are (1) the employment of smart materials to make metamaterials active, (2) proposing a method of how to realize this using production materials and (3) employing these methods to build a small metamaterial demonstrator that functions both as the actuator and the structure. In this work this was done by designing and constructing a tube shaped metamaterial demonstrator of a high precision positioning system. The 3D geometry of the metamaterial was built by layering planar pre-fabricated structures which use smart material for actuation. The design of the unit cells can be implemented in metamaterial of any shape and allows for miniaturization, which extends its applicability. The metamaterial was capable of vertical displacements. The constructed metamaterial tube was able to bend itself. Measured maximum amplitudes of a single layer, and the three layered stack were respectively 4.60 μm and 6.91 μm. Roll movement of the top layer of the stack was achieved with a lowest point of -0.13 μm and a highest point of 8.49 μm. The system showed that smart materials are a suitable choice to make metamaterial active, and that active metamaterial could be produced using production material. The planar approach for design and fabrication, provides a relatively simple and fast method for building metamaterial in general.