A reconfigurable tactile display based on polymer MEMS technology

This research focuses on the development of polymer microfabrication technologies for the realization of two major components of a pneumatic tactile display: a microactuator array and a complementary microvalve (control) array. The concept, fabrication, and characterization of a kinematically-stabilized polymeric microbubble actuator (¡°endoskeletal microbubble actuator¡±) were presented. A systematic design and modeling procedure was carried out to generate an optimized geometry of the corrugated diaphragm to satisfy membrane deflection, force, and stability requirements set forth by the tactile display goals. A refreshable Braille cell as a tactile display prototype has been developed based on a 2x3 endoskeletal microbubble array and an array of commercial valves. The prototype can provide both a static display (which meets the displacement and force requirement of a Braille display) and vibratory tactile sensations. Along with the above capabilities, the device was designed to meet the criteria of lightness and compactness to permit portable operation. The design is scalable with respect to the number of tactile actuators while still being simple to fabricate. In order to further reduce the size and cost of the tactile display, a microvalve array can be integrated into the tactile display system to control the pneumatic fluid that actuates the microbubble actuator. A piezoelectrically-driven and hydraulically-amplified polymer microvalve has been designed, fabricated, and tested. An incompressible elastomer was used as a solid hydraulic medium to convert the small axial displacement of a piezoelectric actuator into a large valve head stroke while maintaining a large blocking force. The function of the microvalve as an on-off switch for a pneumatic microbubble tactile actuator was demonstrated. To further reduce the cost of the microvalve, a laterally-stacked multilayer PZT actuator has been fabricated using diced PZT multilayer, high aspect ratio SU-8 photolithography, and molding of electrically conductive polymer composite electrodes.Ph.D.Committee Chair: Allen,Mark; Committee Member: Bucknall,David; Committee Member: Book,Wayne; Committee Member: Griffin,Anselm; Committee Member: Yao,Donggan

Hybrid energy harvesting based on cymbal and wagon wheel inspiration

The demand for self-sufficient electronic devices is increasing as well as the overall energy use, and such demands are pushing technology forward, especially in effective energy harvesting. A novel hybrid Energy Harvesting System (EHS) has been proposed and analysed in this paper. It has been demonstrated that the EHS is capable of converting enough energy to power a typical MEMS device. This has been achieved through unification of the nine Cymbal Energy Harvester (CEH) array, as an energy harvesting core, and Shape Memory Alloy (SMA) active elements, acting as a source of force stimulated by the environmental changes. A Finite Element Model (FEM) was developed for the CEH, which was verified and used for the analysis of CEH’s response to the change of the end-cap material. This was followed by the FEM for the EHS used for analysis of the location of SMA wires and force generated by each wire individually and then all together. As a further optimisation of the EHS a novel Wagon Wheel design was explored in terms of its energy harvesting capabilities. As expected, due to the increased displacement, an increase in the power output was achieved

Dynamics characterisation of cymbal transducers for power ultrasonics applications

A class V cymbal flextensional transducer is composed of a piezoceramic disc sandwiched between two cymbal-shaped shell end-caps. Depending on the type of piezoceramic, there exists a maximum voltage that can be reached without depolarisation, but also, at higher voltage levels, amplitude saturation can occur. In addition, there is a restriction imposed by the mechanical strength of the bonding agent. The effects of input voltage level on the vibration response of two cymbal transducers are studied. The first cymbal transducer has a standard configuration of end-caps bonded to a piezoceramic disc, whereas the second cymbal transducer is a modified design which includes a metal ring to improve the mechanical coupling with the end-caps, to enable the transducer to operate at higher voltages, thereby generating higher displacement amplitudes. This would allow the transducer to be suitable for power ultrasonics applications. Furthermore, the input voltages to each transducer are increased incrementally to determine the linearity in the dynamic responses. Through a combination of numerical modelling and experiments, it is shown how the improved mechanical coupling in the modified cymbal transducer allows higher vibration amplitudes to be reached

A smart 3D ultrasonic actuator for unmanned vehicle guidance industrial applications

A smart piezoelectric ultrasonic actuator with multidegree of freedom for unmanned vehicle guidance industrial applications is presented in this paper. The proposed actuator is aiming to increase the visual spotlight angle of digital visual data capture transducer. Furthermore research are still undertaken to integrate the actuator with an infrared sensor, visual data capture digital transducers and obtain the trajectory of motion control algorithm. The actuator consists of three main parts, the stator, rotor and housing unit. The stator is a piezoelectric ring made from S42 piezoelectric material, bonded to three electrodes made from a material that has a close Characteristics to the S42. The rotor is a ball made from steel material. The actuator working principles is based on creating micro elliptical motions of surface points, generated by superposition of longitudinal and bending vibration modes, of oscillating structures. Transferring this motion from flexible ring transducer through the three electrodes, to the attached rotor, create 3D motions. The actuator Design, structures, working principles and finite element analysis are discussed in this paper. A prototype of the actuator was fabricated and its characteristics measured. Experimental tests showed the ability of the developed prototype to provide multidegree of freedom with typical speed of movement equal to 35 rpm, a resolution of less than 5μm and maximum load of 3.5 Newton. These characteristics illustrated the potential of the developed smart actuator, to gear the spotlight angle of digital visual data capture transducers and possible improvement that such microactuator technology could bring to the unmanned vehicle guidance and machine vision industrial applications

A smart ultrasonic actuator with multidegree of freedom for autonomous vehicle guidance industrial applications

A piezoelectric ultrasonic actuator with multidegree of freedom for autonomous vehicle guidance industrial applications is presented in this paper. The actuator is aiming to increase the visual spotlight angle of digital visual data capture transducer. It consists of three main parts, the stator, rotor and housing unit. The stator is a piezoelectric ring made from S42 piezoelectric ceramics material, bonded to three electrodes made from a material that has a close Characteristics to the S42. The rotor is a ball made from stainless steel materials. The actuator working principles is based on creating micro elliptical motions of surface points, generated by superposition of longitudinal and bending vibration modes, of oscillating structures. Transferring this motion from flexible ring transducer through the three electrodes, to the attached rotor, create 3D motions. The actuator Design, structures, working principles and finite element analysis are discussed in this paper. A prototype of the actuator was fabricated and its characteristics measured. Experimental tests showed the ability of the developed prototype to provide multidegree of freedom with typical speed of movement equal to 35 rpm, a resolution of less than 5μm and maximum load of 3.5 Newton. These characteristics illustrated the potential of the developed smart actuator, to gear the spotlight angle of digital visual data capture transducers and possible improvement that such micro-actuator technology could bring to the autonomous vehicle guidance and machine vision industrial applications. Furthermore research are still undertaken to develop a universal control prototype, integrate the actuator with an infrared sensor, visual data capture digital transducers and obtain the trajectory of motion control algorithm

Miniature ultrasonic bone cutting device based on a cymbal transducer

Ultrasonic cutting devices have been successfully used in several industries, especially the food industry. This knowledge, developed for industrial procedures, has been exported to other areas where it is having great impact. In medicine, during the last 30 years, di↵erent ultrasonic devices have been designed for a wide variety of surgical procedures involving soft tissue, and even more recently for cutting of bone. The increasing numbers of surgeons adopting ultrasonic devices as the device of choice has in turn increased the demand for devices which are able to be used increasingly in new procedures with more dicult to access surgical sites. Currently, ultrasonic cutting devices consist of a Langevin piezoelectric transducer attached to a cutting blade both tuned to resonate in a longitudinal mode at a low ultrasonic frequency, usually in the 20-50 kHz range. The first commercial ultrasonic devices for bone cutting applications, designed by the Italian company Mectron and called Piezosurgeryr, were based on a Langevin piezoelectric transducer. Langevin transducers incorporate a piezoceramic stack capable of delivering a few microns of vibration amplitude, and therefore the transducer and the device as a whole must be resonant to achieve the required ultrasonic displacement amplitude at the cutting tip. Because the ultrasonic blade is a tuned component its length must be a half-wavelength or a multiple of the half-wavelength at the driving frequency. Also, because Langevin transducers can only deliver a few microns of vibration amplitude, the blade profile must be carefully designed to provide sucient vibration amplitude gain to meet the requirements of the material to be cut. Therefore the cutting blade itself incorporates high amplitude gain, which can lead to very high stresses, and the design of the blade geometry is somewhat restricted by the requirement for resonance. These two geometry requirements can be very restrictive in the design of devices; a half- wavelength at a low ultrasonic frequency leads to quite a large cutting device and profiling for high gain leads to very high stresses. This thesis investigates adapting the class V flextensional ‘cymbal’ transducer for power ultrasonic applications. The cymbal transducer consists of piezoelectric rings bonded to two end-caps with truncated conical shape. When the ring contracts radially under an AC voltage, the end-caps flex providing an amplified motion normal to the cap surfaces. This thesis introduces a new prototype of an ultrasonic cutting device for bone surgery based on a cymbal transducer, optimised for use in power ultrasonics applications, which removes many of the geometrical restrictions on the cutting tip. For the proposed application, a cutting blade is attached to one of the vibrating end-caps with little e↵ect on the operational frequency. Thus, the blade behaves nearly as a rigid body, without the need to be a tuned component of the device. The enormous benefit of this technology is that the cutting blade design can focus more closely on delivering the best interaction between the blade and bone to provide a highly accurate cut, and also the ultrasonic device can be miniaturised to allow the design of devices for delicate orthopaedic procedures involving minimal access surgery. The results show how the cymbal transducer can excite suciently high vibration displacement amplitude at lower driving voltages, by adapting the configuration of the cymbal to remove the problem of epoxy layer debonding and by optimising the cymbal end-caps and geometry through finite element modelling supported with experimental vibration characterisation. Preliminary trials of the resulting prototype ultrasonic bone cutting device, which operates near to 25 kHz, are presented to illustrate the success of this novel device design

Structural design and physical mechanism of axial and radial sandwich resonators with piezoelectric ceramics : a review

Piezoelectric ceramics are inexpensive functional materials which are widely used in sonar detection, home appliances, meteorological detection, telemetry and environmental protection and other applications. Sensors fabricated from these materials are compact and have fast response characteristics. Their underlying functional methodology is based on the direct piezoelectric effect whereby very small mechanical vibration signals are converted into electrical signals. Piezoelectric resonators are based on the reverse piezoelectric effect and they are widely used for the control of precision instruments and precision machinery, microelectronic components, bioengineering devices and other in applications requiring components to provide precision control of the relevant functional mechanism. In this paper, the structural evolution and design mechanism of sandwich resonators based on piezoelectric materials are reviewed, and the advantages and disadvantages of different structures are compared and analyzed. The goal is to provide a comprehensive reference for the selection, application and promotion of piezoelectric resonators and for future structural innovation and mechanism research relevant to sandwich resonators

Creative design and modelling of large-range translation compliant parallel manipulators

Compliant parallel mechanisms/manipulators (CPMs) are parallel manipulators that transmit motion/load by deformation of their compliant members. Due to their merits such as the eliminated backlash and friction, no need for lubrication, reduced wear and noise, and monolithic configuration, they have been used in many emerging applications as scanning tables, bio-cell injectors, nano-positioners, and etc. How to design large-range CPMs is still a challenging issue. To meet the needs for large-range translational CPMs for high-precision motion stages, this thesis focuses on the systematic conceptual design and modelling of large-range translational CPMs with distributed-compliance. Firstly, several compliant parallel modules with distributed-compliance, such as spatial multi-beam modules, are identified as building blocks of translational CPMs. A normalized, nonlinear and analytical model is then derived for the spatial multi-beam modules to address the non-linearity of load-equilibrium equations. Secondly, a new design methodology for translational CPMs is presented. The main characteristic of the proposed design approach is not only to replace kinematic joints as in the literature, but also to replace kinematic chains with appropriate multiple degrees-of-freedom (DOF) compliant parallel modules. Thirdly, novel large-range translational CPMs are constructed using the proposed design methodology and identified compliant parallel modules. The proposed novel CPMs include, for example, a 1-DOF compliant parallel gripper with auto-adaptive grasping function, a stiffness-enhanced XY CPM with a spatial compliant leg, and an improved modular XYZ CPM using identical spatial double four-beam modules. Especially, the proposed XY CPM and XYZ CPM can achieve a 10mm’s motion range along each axis in the case studies. Finally, kinematostatic modelling of the proposed translational CPMs is presented to enable rapid performance characteristic analysis. The proposed analytical models are also compared with finite element analysis

Integrated Actuation And Energy Harvesting In Prestressed Piezoelectric Synthetic Jets

With the looming energy crisis compounded by the global economic downturn there is an urgent need to increase energy efficiency and to discover new energy sources. An approach to solve this problem is to improve the efficiency of aerodynamic vehicles by using active flow control tools such as synthetic jet actuators. These devices are able to reduce fuel consumption and streamlined vehicle design by reducing drag and weight, and increasing maneuverability. Hence, the main goal of this dissertation is to study factors that affect the efficiency of synthetic jets by incorporating energy harvesting into actuator design using prestressed piezoelectric composites. Four state-of-the-art piezoelectric composites were chosen as active diaphragms in synthetic jet actuators. These composites not only overcome the inherent brittle and fragile nature of piezoelectric materials but also enhance domain movement which in turn enhances intrinsic contributions. With these varying characteristics among different types of composites, the intricacies of the synthetic jet design and its implementation increases. In addition the electrical power requirements of piezoelectric materials make the new SJA system a coupled multiphysics problem involving electro–mechanical and structural–fluid interactions. Due to the nature of this system, a design of experiments approach, a method of combining experiments and statistics, is utilized. Geometric and electro-mechanical factors are investigated using a fractional factorial design with peak synthetic jet velocity as a response variable. Furthermore, energy generated by the system oscillations is harvested with a prestressed composite and a piezo-polymer. Using response surface methodology the process is optimized under different temperatures and pressures to simulate harsh environmental conditions. Results of the fractional factorial experimental design showed that cavity dimensions and type of signal used to drive the synthetic jet actuator were statistically significant factors when studying peak jet velocity. The Bimorph (~50m/s) and the prestressed metal composite (~45m/s) generated similar peak jet velocities but the later is the most robust of all tested actuators. In addition, an alternate input signal to the composite, a sawtooth waveform, leads to jets formed with larger peak velocities at frequencies above 15Hz. The optimized factor levels for the energy harvesting process were identified as 237.6kPa, 3.7Hz, 1MΩ and 12°C and the power density measured at these conditions was 24.27µW/mm3. Finally, the SJA is integrated with an energy harvesting system and the power generated is stored into a large capacitor and a rechargeable battery. After approximately six hours of operation 5V of generated voltage is stored in a 330µF capacitor with the prestressed metal composite as the harvester. It is then demonstrated that energy harvested from the inherent vibrations of a SJA can be stored for later use. Then, the system proposed in this dissertation not only improves on the efficiency of aerodynamic bodies, but also harvests energy that is otherwise wasted