Examination of the performance characteristics of velostat as an in-socket pressure sensor

Velostat is a low-cost, low-profile electrical bagging material with piezoresistive properties, making it an attractive option for in-socket pressure sensing. The focus of this research was to explore the suitability of a Velostat-based system for providing real-time socket pressure profiles. The prototype system performance was explored through a series of bench tests to determine properties including accuracy, repeatability and hysteresis responses, and through participant testing with a single subject. The fabricated sensors demonstrated mean accuracy errors of 110 kPa and significant cyclical and thermal drift effects of up to 0.00715 V/cycle and leading to up to a 67% difference in voltage range respectively. Despite these errors the system was able to capture data within a prosthetic socket, aligning to expected contact and loading patterns for the socket and amputation type. Distinct pressure maps were obtained for standing and walking tasks displaying loading patterns indicative of posture and gait phase. The system demonstrated utility for assessing contact and movement patterns within a prosthetic socket, potentially useful for improvement of socket fit, in a low cost, low profile and adaptable format. However, Velostat requires significant improvement in its electrical properties before proving suitable for accurate pressure measurement tools in lower limb prosthetics

Microrobots for wafer scale microfactory: design fabrication integration and control.

Future assembly technologies will involve higher automation levels, in order to satisfy increased micro scale or nano scale precision requirements. Traditionally, assembly using a top-down robotic approach has been well-studied and applied to micro-electronics and MEMS industries, but less so in nanotechnology. With the bloom of nanotechnology ever since the 1990s, newly designed products with new materials, coatings and nanoparticles are gradually entering everyone’s life, while the industry has grown into a billion-dollar volume worldwide. Traditionally, nanotechnology products are assembled using bottom-up methods, such as self-assembly, rather than with top-down robotic assembly. This is due to considerations of volume handling of large quantities of components, and the high cost associated to top-down manipulation with the required precision. However, the bottom-up manufacturing methods have certain limitations, such as components need to have pre-define shapes and surface coatings, and the number of assembly components is limited to very few. For example, in the case of self-assembly of nano-cubes with origami design, post-assembly manipulation of cubes in large quantities and cost-efficiency is still challenging. In this thesis, we envision a new paradigm for nano scale assembly, realized with the help of a wafer-scale microfactory containing large numbers of MEMS microrobots. These robots will work together to enhance the throughput of the factory, while their cost will be reduced when compared to conventional nano positioners. To fulfill the microfactory vision, numerous challenges related to design, power, control and nanoscale task completion by these microrobots must be overcome. In this work, we study three types of microrobots for the microfactory: a world’s first laser-driven micrometer-size locomotor called ChevBot，a stationary millimeter-size robotic arm, called Solid Articulated Four Axes Microrobot (sAFAM), and a light-powered centimeter-size crawler microrobot called SolarPede. The ChevBot can perform autonomous navigation and positioning on a dry surface with the guidance of a laser beam. The sAFAM has been designed to perform nano positioning in four degrees of freedom, and nanoscale tasks such as indentation, and manipulation. And the SolarPede serves as a mobile workspace or transporter in the microfactory environment

Capacitive Micromachined Ultrasound Transducers for Non-Destructive Testing Applications

The need for using ultrasound non-destructive testing (NDT) to characterize, test and detect flaws within metals, led us to utilize Capacitive Micromachined Ultrasound Transducers (CMUTs) in the ultrasound NDT field. This is due to CMUT's large bandwidths and high receive sensitivity, to be a suitable substitute for piezoelectric (PZT) transducers in NDT applications. The basic operational test of CMUTs, conducted in this research, was carried out based on a pulse-echo technique by propagating acoustic pulses into an object and analyzing the reflected signals. Thus, characterizing the tested material, measuring its dimension, and detecting flaws within it can be achieved. Throughout the course of this research, the fundamental parameters of CMUT including pull-in voltage and resonance frequency were initially calculated analytically and using Finite Element Analysis (FEA). Afterward, the CMUT was fabricated out of two mechanically bonded wafers. The device's movable membrane (top electrode) and stationary electrode (bottom electrode) were made out of Boron-doped Silicon. The two electrodes were electrically isolated by an insulation layer containing a sealed gap. The CMUT was then tested and characterized to analyze its performance for NDT applications. In-immersion characterization revealed that the 2.22 MHz CMUT obtained a -6 dB fractional bandwidth of 189%, and a receive sensitivity of 31.15 mV/kPa, compared to 45% and 4.83 mV/kPa of the PZT probe. A pulse-echo test, performed to examine an aluminum block with and without flaws, showed success in distinguishing the surfaces and the flaws of the tested sample

Elastic Inflatable Actuators for Soft Robotic Applications

The 20th century’s robotic systems have been made out of stiff materials and much of the developments in the field have pursued ever more accurate and dynamic robots which thrive in industrial automation settings and will probably continue to do so for many decades to come. However, the 21st century’s robotic legacy may very well become that of soft robots. This emerging domain is characterized by continuous soft structures that simultaneously fulfil the role of robotic link and robotic actuator, where prime focus is on design and fabrication of the robotic hardware instead of software control to achieve a desired operation. These robots are anticipated to take a prominent role in delicate tasks where classic robots fail, such as in minimally invasive surgery, active prosthetics and automation tasks involving delicate irregular objects. Central to the development of these robots is the fabrication of soft actuators to generate movement. This paper reviews a particularly attractive type of soft actuators that are driven by pressurized fluids. These actuators have recently gained substantial traction on the one hand due to the technology push from better simulation tools and new manufacturing technologies including soft-lithography and additive manufacturing, and on the other hand by a market pull from the applications listed above. This paper provides an overview of the different advanced soft actuator configurations, their design, fabrication and applications.This research is supported by the Fund for Scientific Research-Flanders (FWO), and the European Research Council (ERC starting grant HIENA)

Where and how 3D printing is used in teaching and education

The emergence of additive manufacturing and 3D printing technologies is introducing industrial skills deficits and opportunities for new teaching practices in a range of subjects and educational settings. In response, research investigating these practices is emerging across a wide range of education disciplines, but often without reference to studies in other disciplines. Responding to this problem, this article synthesizes these dispersed bodies of research to provide a state‐of‐the‐art literature review of where and how 3D printing is being used in the education system. Through investigating the application of 3D printing in schools, universities, libraries and special education settings, six use categories are identified and described: (1) to teach students about 3D printing; (2) to teach educators about 3D printing; (3) as a support technology during teaching; (4) to produce artefacts that aid learning; (5) to create assistive technologies; and (6) to support outreach activities. Although evidence can be found of 3D printing‐based teaching practices in each of these six categories, implementation remains immature, and recommendations are made for future research and education policy.This work was supported by the Engineering and Physical Sciences Research Council [number EP/K039598/1]

Elastic Inflatable Actuators for Soft Robotic Applications

The 20th century’s robotic systems have been made out of stiff materials and much of the developments in the field have pursued ever more accurate and dynamic robots which thrive in industrial automation settings and will probably continue to do so for many decades to come. However, the 21st century’s robotic legacy may very well become that of soft robots. This emerging domain is characterized by continuous soft structures that simultaneously fulfil the role of robotic link and robotic actuator, where prime focus is on design and fabrication of the robotic hardware instead of software control to achieve a desired operation. These robots are anticipated to take a prominent role in delicate tasks where classic robots fail, such as in minimally invasive surgery, active prosthetics and automation tasks involving delicate irregular objects. Central to the development of these robots is the fabrication of soft actuators to generate movement. This paper reviews a particularly attractive type of soft actuators that are driven by pressurized fluids. These actuators have recently gained substantial traction on the one hand due to the technology push from better simulation tools and new manufacturing technologies including soft-lithography and additive manufacturing, and on the other hand by a market pull from the applications listed above. This paper provides an overview of the different advanced soft actuator configurations, their design, fabrication and applications.This research is supported by the Fund for Scientific Research-Flanders (FWO), and the European Research Council (ERC starting grant HIENA)

Hardware Implementation of Active Disturbance Rejection Control for Vibrating Beam Gyroscope

Obtaining the approximation of rotation rate form a Z-Axis MEMS gyroscope is a challenging problem. Currently, most commercially available MEMS gyroscopes are operating in an open-loop for purposes of simplicity and cost reduction. However, MEMS gyroscopes are still fairly expensive and are not robust during operation. The purpose of this research was to develop a high-performance and low-cost MEMS gyroscope using analog Active Disturbance Rejection Control (ADRC) system. By designing and implementing analog ADRC both above requirements were satisfied. Analog ADRC provides the fastest response time possible (because the circuit is analog), eliminates both internal and external disturbances, and increases the bandwidth of the gyroscope beyond its natural frequency. On the other hand, the overall design is extremely economical, given that the system is built using pure active and passive analog components. This work, besides achieving high-performance and providing low-cost solution, furnishes two novel designs concepts. First, Active Disturbance Rejection Controller can now be build using pure analog circuit, which has never been done before. Second, it is the first time that the advanced controller has been successfully implemented in hardware to control an inertial rate sensor like gyroscope. This work provides a novel solution to applications that require high-performance and low-cost inertial sensor

Selective Resistive Sintering: A Novel Additive Manufacturing Process

Selective laser sintering (SLS) is one of the most popular 3D printing methods that uses a laser to pattern energy and selectively sinter powder particles to build 3D geometries. However, this printing method is plagued by slow printing speeds, high power consumption, difficulty to scale, and high overhead expense. In this research, a new 3D printing method is proposed to overcome these limitations of SLS. Instead of using a laser to pattern energy, this new method, termed selective resistive sintering (SRS), uses an array of microheaters to pattern heat for selectively sintering materials. Using microheaters offers significant power savings, significantly reduced overhead cost, and increased printing speed scalability. The objective of this thesis is to obtain a proof of concept of this new method. To achieve this objective, we first designed a microheater to operate at temperatures of 600⁰C, with a thermal response time of ~1 ms, and even heat distribution. A packaging device with electrical interconnects was also designed, fabricated, and assembled with necessary electrical components. Finally, a z-stage was designed to control the airgap between the printhead and the powder particles. The whole system was tested using two different scenarios. Simulations were also conducted to determine the feasibility of the printing method. We were able to successfully operate the fabricated microheater array at a power consumption of 1.1W providing significant power savings over lasers. Experimental proof of concept was unsuccessful due to the lack of precise control of the experimental conditions, but simulation results suggested that selectivity sintering nanoparticles with the microheater array was a viable process. Based on our current results that the microheater can be operated at ~1ms timescale to sinter powder particles, it is believed this new process can potentially be significantly quicker than selective laser sintering by increasing the number of microheater elements in the array. The low cost of a microheater array printhead will also make this new process affordable. This thesis presented a pioneering study on the feasibility of the proposed SRS process, which could potentially enable the development of a much more affordable and efficient alternative to SLS

Hardware Implementation of Active Disturbance Rejection Control for Vibrating Beam Gyroscope

Obtaining the approximation of rotation rate form a Z-Axis MEMS gyroscope is a challenging problem. Currently, most commercially available MEMS gyroscopes are operating in an open-loop for purposes of simplicity and cost reduction. However, MEMS gyroscopes are still fairly expensive and are not robust during operation. The purpose of this research was to develop a high-performance and low-cost MEMS gyroscope using analog Active Disturbance Rejection Control (ADRC) system. By designing and implementing analog ADRC both above requirements were satisfied. Analog ADRC provides the fastest response time possible (because the circuit is analog), eliminates both internal and external disturbances, and increases the bandwidth of the gyroscope beyond its natural frequency. On the other hand, the overall design is extremely economical, given that the system is built using pure active and passive analog components. This work, besides achieving high-performance and providing low-cost solution, furnishes two novel designs concepts. First, Active Disturbance Rejection Controller can now be build using pure analog circuit, which has never been done before. Second, it is the first time that the advanced controller has been successfully implemented in hardware to control an inertial rate sensor like gyroscope. This work provides a novel solution to applications that require high-performance and low-cost inertial sensor

Hardware Implementation of Active Disturbance Rejection Control for Vibrating Beam Gyroscope

Obtaining the approximation of rotation rate form a Z-Axis MEMS gyroscope is a challenging problem. Currently, most commercially available MEMS gyroscopes are operating in an open-loop for purposes of simplicity and cost reduction. However, MEMS gyroscopes are still fairly expensive and are not robust during operation. The purpose of this research was to develop a high-performance and low-cost MEMS gyroscope using analog Active Disturbance Rejection Control (ADRC) system. By designing and implementing analog ADRC both above requirements were satisfied. Analog ADRC provides the fastest response time possible (because the circuit is analog), eliminates both internal and external disturbances, and increases the bandwidth of the gyroscope beyond its natural frequency. On the other hand, the overall design is extremely economical, given that the system is built using pure active and passive analog components. This work, besides achieving high-performance and providing low-cost solution, furnishes two novel designs concepts. First, Active Disturbance Rejection Controller can now be build using pure analog circuit, which has never been done before. Second, it is the first time that the advanced controller has been successfully implemented in hardware to control an inertial rate sensor like gyroscope. This work provides a novel solution to applications that require high-performance and low-cost inertial sensor