Additive manufacturing (3D print) of air-coupled diaphragm ultrasonic transdrucers

Air-coupled ultrasound is a non-contact technology that has become increasingly common in Non Destructive Evaluation (NDE) and material evaluation. Normally, the bandwidth of a conventional transducer can be enhanced, but with a cost to its sensitivity. However, low sensitivity is very disadvantageous in air-coupled devices. This thesis proposes a methodology for improving the bandwidth of an air-coupled micro-machined ultrasonic transducer (MUT) without sensitivity loss by connecting a number of resonating pipes of various length to a cavity in the backplate. This design is inspired by the pipe organ musical instrument, where the resonant frequency (pitch) of each pipe is mainly determined by its length. The −6 dB bandwidth of the "pipe organ" inspired air-coupled transducer is 55.7% and 58.5% in transmitting and receiving modes, respectively, which is ∼5 times wider than a custom-built standard device. After validating the concept via a series of single element low-frequency prototypes, two improved designs: the multiple element and the high-frequency single element pipe organ transducers were simulated in order to tailor the pipe organ design to NDE applications.Although the simulated and experimental performance of the pipe organ inspired transducers are proved to be significantly better than the conventional designs, conventional micro-machined technologies are not able to satisfy their required 3D manufacturing resolution. In recent years, there has been increasing interest in using additive manufacturing (3D printing) technology to fabricate sensors and actuators due to rapid prototyping, low-cost manufacturing processes, customized features and the ability to create complex 3D geometries at micrometre scale. This work combines the ultrasonic diaphragm transducer design with a novel stereolithographic additive manufacturing technique. This includes developing a multi-material fabrication process using a commercial digital light processing printer and optimizing the formula of custom-built functional (conductive and piezoelectric) materials. A set of capacitive acoustic and ultrasonic transducers was fabricated using the additive manufacturing technology. The additive manufactured capacitive transducers have a receiving sensitivity of up to 0.4 mV/Pa at their resonant frequency.Air-coupled ultrasound is a non-contact technology that has become increasingly common in Non Destructive Evaluation (NDE) and material evaluation. Normally, the bandwidth of a conventional transducer can be enhanced, but with a cost to its sensitivity. However, low sensitivity is very disadvantageous in air-coupled devices. This thesis proposes a methodology for improving the bandwidth of an air-coupled micro-machined ultrasonic transducer (MUT) without sensitivity loss by connecting a number of resonating pipes of various length to a cavity in the backplate. This design is inspired by the pipe organ musical instrument, where the resonant frequency (pitch) of each pipe is mainly determined by its length. The −6 dB bandwidth of the "pipe organ" inspired air-coupled transducer is 55.7% and 58.5% in transmitting and receiving modes, respectively, which is ∼5 times wider than a custom-built standard device. After validating the concept via a series of single element low-frequency prototypes, two improved designs: the multiple element and the high-frequency single element pipe organ transducers were simulated in order to tailor the pipe organ design to NDE applications.Although the simulated and experimental performance of the pipe organ inspired transducers are proved to be significantly better than the conventional designs, conventional micro-machined technologies are not able to satisfy their required 3D manufacturing resolution. In recent years, there has been increasing interest in using additive manufacturing (3D printing) technology to fabricate sensors and actuators due to rapid prototyping, low-cost manufacturing processes, customized features and the ability to create complex 3D geometries at micrometre scale. This work combines the ultrasonic diaphragm transducer design with a novel stereolithographic additive manufacturing technique. This includes developing a multi-material fabrication process using a commercial digital light processing printer and optimizing the formula of custom-built functional (conductive and piezoelectric) materials. A set of capacitive acoustic and ultrasonic transducers was fabricated using the additive manufacturing technology. The additive manufactured capacitive transducers have a receiving sensitivity of up to 0.4 mV/Pa at their resonant frequency

Two-Photon-Polymerization for Powder Processing of Ceramics

Diese Arbeit ist ein Proof-of-Concept. Aus vorangegangenen Experimenten und der Literatur war zu erahnen, dass ein klassisch gemahlener keramischer Schlicker nicht für die Verwendung mit der Zwei-Photonen-Polymerisation geeignet ist. Die keramischen Partikel können nicht klein genug aufgemahlen werden, um die Lichtstreuung auszuhebeln, welche essentiell für den Prozess ist. Keramische Partikel in geeigneter Größe finden sich in kommerziell erhältlichen Suspensionen. In dieser Studie wurden vor allem Aluminium- und Zirkonoxid-Partikel verwendet um daraus Aluminium-verstärktes Zirkonoxid (ATZ) herzustellen. Die Partikel sind in Wasser suspendiert und mussten erst noch in einen photo-vernetzbaren Schlicker überführt werden. Dies erfolgte mittels der wasserlöslichen Acrylamid (AM) und N,N'-Methylenbisacrylamid (MBAM) und eines geeigneten Photoinitiators. Der entstandene Schlicker wurde hinsichtlich seiner rheologischen und optischen Eigenschaften untersucht und stellte sich als für die Zwei-Photonen-Polymerisation geeignet heraus. Während und nach dem Drucken müssen verschiedene Aspekte beachtet werden damit die gewünschten Geometrien zerstörungsfrei in eine keramische Struktur überführt werden können. Die Prozesse konnten so weit optimiert werden, dass eine dreidimensionale SchwarzP Struktur gedruckt werden konnten, die nur noch leicht verzerrt ist durch den unterschiedlich starken Schrumpf zwischen Grundplatte und Volumen. Der keramische Charakter der Strukturen konnte mittels Energiedispersiver-Röntgenspektroskopie (EDX) nachgewiesen werden. Dabei konnte unter anderem festgestellt werden, dass die beiden keramischen Spezies Aluminium- und Zirkonoxid sich während des Sinterprozesses entmischen und große Kristallite bilden. Daraus ließ sich ableiten, dass der Sinterprozess noch weiter optimiert werden kann. Zusammengefasst ergeben die Ergebnisse einen positiven Proof-of-Concept: Es wurde ein heterogener Schlicker entwickelt, welcher zum einen flüssig, photo-vernetzbar und transparent ist und zum anderen genügend keramische Partikel enthält, um stabile Strukturen zu sintern. Damit wird der 3D-Druck hochpräziser keramischer Bauteile mit enormen Freiheitsgraden ermöglicht, was mit keiner anderen Technologie erreichbar ist. Die wichtigste Grundlage dafür sind stabilisierte Suspensionen von keramischen Nano-Partikeln.No industry stays untouched by additive manufacturing and its huge potential to revolutionize our manufacturing processes. 3D-printed ceramic parts are of rising interest, due to their unique chemical, mechanical and electrical properties. The Two-Photon-Polymerization as a stereolithography technology stands out with its high resolution in the small micrometer- down to nanometerrange and its operation freedom to print freely in the three-dimensional volume. Utilizing this process to produce high precision ceramic parts opens a new order of magnitude to ceramic manufacturing. Therefore, a completely new resin is needed, which meets the requirements of the Two-Photon-Polymerization and ceramic processing. In this study a resin was developed regarding the rheological, optical and photocuring requirements and printed into three-dimensional figures. That ought to be debinded and sintered to gain fully ceramic three dimensional structures of alumina toughened zirconia (ATZ), as an example of techn

3D microfabrication of biological machines

The burgeoning field of additive manufacturing, or “3D printing”, centers on the idea of creating three-dimensional objects from digital models. While conventional manufacturing approaches rely on modifying a base material via subtractive processes such as drilling or cutting, 3D printing creates three-dimensional objects through successive deposition of two- dimensional layers. By enabling rapid fabrication of complex objects, 3D printing is revolutionizing the fields of engineering design and manufacturing. This thesis details the development of a projection-based stereolithographic 3D printing apparatus capable of high- resolution patterning of living cells and cell signals dispersed in an absorbent hydrogel polymer matrix in vitro. This novel enabling technology can be used to create model cellular systems that lead to a quantitative understanding of the way cells sense, process, and respond to signals in their environment. The ability to pattern cells and instructive biomaterials into complex 3D patterns has many applications in the field of tissue engineering, or “reverse engineering” of cellular systems that replicate the structure and function of native tissue. While the goal of reverse engineering native tissue is promising for medical applications, this idea of building with biological components concurrently brings about a new discipline: “forward engineering” of biological machines and systems. In addition to rebuilding existing systems with cells, this technology enables the design and forward engineering of novel systems that harness the innate dynamic abilities of cells to self-organize, self-heal, and self-replicate in response to environmental cues. This thesis details the development of skeletal and cardiac muscle based bioactuators that can sense external electrical and optical signals and demonstrate controlled locomotive behavior in response to them. Such machines, which can sense, process, and respond to signals in a dynamic environment, have a myriad array of applications including toxin neutralization and high throughput drug testing in vitro and drug delivery and programmable tissue engineered implants in vivo. A synthesis of two fields, 3D printing and tissue engineering, has brought about a new discipline: using microfabrication technologies to forward engineer biological machines and systems capable of complex functional behavior. By introducing a new set of “building blocks” into the engineer’s toolbox, this new era of design and manufacturing promises to open up a field of research that will redefine our world

Shear Induced Fiber Alignment and Acoustic Nanoparticle Micropatterning during Stereolithography

The stereolithograpy method, which consists of a light source to polymerize the liquid photocurable resin, can produce structures with complex shapes. Most of the produced structures are unreinforced neat pieces. The addition of reinforcement, such as fibers and particles are regularly utilized to improve mechanical properties and electrical conductivity of the printed parts. Added fibers might be chosen as short or continuous fibers and the properties of the reinforced composite materials can be significantly improved by aligning the fibers in preferred directions. The first aim of this dissertation is to enhance the tensile and flexural strengths of the 3d printed composites by using shear induced alignment of short fibers. The second aim is to print parts with conductive embedded microstructures by utilizing acoustic patterning of conductive particles. Both aims are utilized during the stereolithography process.A lateral oscillation mechanism, which is inspired by large amplitude oscillatory shear test, was designed to generate shear flow. The alignment method, which combines the lateral oscillation mechanism with 3d printed wall patterns, is developed to utilized shear flow to align the fibers in the patterned wall direction. Shear rate amplitude, fiber concentration, and patterned wall angle were considered as parameters during this study.The stereolithography device incorporated with oscillation mechanism was utilized to produce short fiber reinforced ceramic composites and short nanofiber reinforced polymer composites. Nickel coated short carbon fibers, alumina and silica short fibers were used to reinforce the ceramic matrix with different fiber contents. The printed walls were demonstrated to align the short fibers parallel to the wall which was different from the oscillation direction up to 45°. The flexural strength of the ceramic matrix was improved with the addition and alignment of the short fibers. The alumina nanofibers were used as reinforcement in the photocurable polymer resin. The alumina nanofibers were treated with a silane coupling agent to improve interfacial bond between alumina fibers and polymer resin matrix. The aligned specimen demonstrated improvement in tensile strength with increasing nanowire content and their alignment.A hexagon shaped acoustic tweezer was incorporated into the stereolithography device to pattern conductive micro- and nanoparticles. This new approach for particle microstructuring via acoustic aligning during the stereolithography was used to produce embedded conductive microstructures in 3d printed parts. The acoustic tweezer was used to pattern the conductive particles into horizontal, 60°, and 120° parallel striped lines. The influence of the particle percentage content onto the electrical resistivity and thickness of the patterned lines were also investigated for different materials such as copper, magnetite, and carbon fiber. The copper patterns show less resistance to electrical currents compare to magnetite and carbon nanofiber patterns. Additionally, the influence of the particle concentration to the height of the pattern was studied and the data was utilized to achieve conductivity along z-axis. Later, this approach was used to fabricate examples of embedded conductive complex 3D microstructures

Peluang kerjaya lepasan politeknik bidang elektronik dan elektrik di sektor perindustrian elektronik di Daerah Batu Pahat

Projek Sarjana ini bertajuk "Pe/uang keljaya /epasan politekni(bidang e/eklronik dan e/eklrik di seklorperinduslrian eleklronik di daerall Balu Pallal ". Secara keseluruhannya, objektifkajian ioi dijalankan untuk melihat pelllang-peluang kerjaya bagi gradllan lepasan politeknik bidang elektronik dan elektrik di sektor perindustrian elek1Tonik di daerah Batu Pahat. Projek Sarjana ini merupakan satu projek yang berbentuk kualitatif di mana responden terdiri daripada Pegawai Sumber Manusia kilang di sektor perindustrian elektTOnik di daerah Batu Pahat yang terpilih. Sepuluh buah kilang yang telah dipilih iaitu kilang SharpRoxy dan SMM di Batu 6, Batu Pahat, kilang Fujitsu di Parit Raja, Batu Pahat , kilang Mitsumi di Bukit Pasir, Batu Pahat, Asahi Electronics (M) Sdn. Bhd, Kawasan Perindustrian Mengkibol, Jalan Kluang, Akari Industries Sdn. Bhd, Jalan Ledang Tg. Laboh Batu Pahat, Alpha Electronics, Jalan Pegawai Batu Pahat, Action ElectTonics Trading Compo ny, Taman Banang Batu Pahat, Nexus Electonics Sdn. Bhd, Taman S. Sulong, Parit Sulong Batu Pahat, Nexquest Sdn. Bhd, Parit Kuari, Parit Raja, Batu Pahat dan Ishi Den Electronics (M) Sdn. Bhd, Kawasan Perindustrian Sri Gading. Data yang diperolehi adalah melalui temubual berstruktur. Dapatan kajian ini menunjukkan bahawa terdapat banyak peluang- peluang kerjaya lepasan politeknik bidang elektronik dan elektrik di sektor perindustrian elek1ronik di daerah Batu Pahat yang boleh diceburi oleh lepasan politeknik bidang elektronik dan elektrik apabila tamat pengajian kelak

Shallots skin peeler machine

Shallots have been a popular food for many centuries. Today, they are valued for their flavor, aroma and taste, being prepared domestically or forming raw materials for a variety of food processors. They are probably the most universally used vegetables in most countries. Shallots skin peeling is an essential step in producing many of the shallot products

A Glance at the Recent Additive Manufacturing Research and Development in China

This paper reviews some of the recent additive manufacturing research and development works in China. A considerable amount of AM research activities in China focuses on directed energy deposition processes, powder bed fusion processes and stereolithography, with much of the effect dedicated to system and application development. Although many of the recent results are not readily available from the literatures published in China, from the available information the areas of focus for research and development could be clearly seen. Despite some speculations, the AM research in China is vibrate and aggressive, with some areas at least several years ahead of the other countries.Mechanical Engineerin