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

Magnetically Driven Micro and Nanorobots

Manipulation and navigation of micro and nanoswimmers in different fluid environments can be achieved by chemicals, external fields, or even motile cells. Many researchers have selected magnetic fields as the active external actuation source based on the advantageous features of this actuation strategy such as remote and spatiotemporal control, fuel-free, high degree of reconfigurability, programmability, recyclability, and versatility. This review introduces fundamental concepts and advantages of magnetic micro/nanorobots (termed here as "MagRobots") as well as basic knowledge of magnetic fields and magnetic materials, setups for magnetic manipulation, magnetic field configurations, and symmetry-breaking strategies for effective movement. These concepts are discussed to describe the interactions between micro/nanorobots and magnetic fields. Actuation mechanisms of flagella-inspired MagRobots (i.e., corkscrew-like motion and traveling-wave locomotion/ciliary stroke motion) and surface walkers (i.e., surface-assisted motion), applications of magnetic fields in other propulsion approaches, and magnetic stimulation of micro/nanorobots beyond motion are provided followed by fabrication techniques for (quasi)spherical, helical, flexible, wire-like, and biohybrid MagRobots. Applications of MagRobots in targeted drug/gene delivery, cell manipulation, minimally invasive surgery, biopsy, biofilm disruption/eradication, imaging-guided delivery/therapy/surgery, pollution removal for environmental remediation, and (bio)sensing are also reviewed. Finally, current challenges and future perspectives for the development of magnetically powered miniaturized motors are discussed

OPTIMAL CONTROL OF OBJECTS ON THE MICRO- AND NANO-SCALE BY ELECTROKINETIC AND ELECTROMAGNETIC MANIPULATION: FOR BIO-SAMPLE PREPARATION, QUANTUM INFORMATION DEVICES AND MAGNETIC DRUG DELIVERY

In this thesis I show achievements for precision feedback control of objects inside micro-fluidic systems and for magnetically guided ferrofluids. Essentially, this is about doing flow control, but flow control on the microscale, and further even to nanoscale accuracy, to precisely and robustly manipulate micro and nano-objects (i.e. cells and quantum dots). Target applications include methods to miniaturize the operations of a biological laboratory (lab-on-a-chip), i.e. presenting pathogens to on-chip sensing cells or extracting cells from messy bio-samples such as saliva, urine, or blood; as well as non-biological applications such as deterministically placing quantum dots on photonic crystals to make multi-dot quantum information systems. The particles are steered by creating an electrokinetic fluid flow that carries all the particles from where they are to where they should be at each time step. The control loop comprises sensing, computation, and actuation to steer particles along trajectories. Particle locations are identified in real-time by an optical system and transferred to a control algorithm that then determines the electrode voltages necessary to create a flow field to carry all the particles to their next desired locations. The process repeats at the next time instant. I address following aspects of this technology. First I explain control and vision algorithms for steering single and multiple particles, and show extensions of these algorithms for steering in three dimensional (3D) spaces. Then I show algorithms for calculating power minimum paths for steering multiple particles in actuation constrained environments. With this microfluidic system I steer biological cells and nano particles (quantum dots) to nano meter precision. In the last part of the thesis I develop and experimentally demonstrate two dimensional (2D) manipulation of a single droplet of ferrofluid by feedback control of 4 external electromagnets, with a view towards enabling feedback control of magnetic drug delivery to reach deeper tumors in the long term. To this end, I developed and experimentally demonstrated an optimal control algorithm to effectively manipulate a single ferrofluid droplet by magnetic feedback control. This algorithm was explicitly designed to address the nonlinear and cross-coupled nature of dynamic magnetic actuation and to best exploit available electromagnetic forces for the applications of magnetic drug delivery

A Numerical Study to Investigate the Hydrodynamic Properties of Nanowire Motion in Liquid

Manipulating micro(nano)-sized entities in liquid environment is a challenging yet necessary task in nanoscience and nanotechnology development. Due to the small dimensions, viscous behavior dominates the micro(nano)-sized obejcts motion. In this study, a computational fluid dynamic (CFD) approach has been used to investigate hydrodynamic effects on a nanowire (NM) translating an rotating about its long and short axis. Several numerical methods dealing with solid motion in fluid, including some CFD methods and Finite element analysis (FEA), have been compared. The change in drag coefficient with NW length, NW diameter, translational velocity, rotation speed, and wall effects has been researched. As a model, nanowires with 1-10 µm dimensions and 50 nm-250 nm diameters were investigated in liquid, with velocities of 0.5-500 µm/s. Nanowire is rotated about its long axis with an angular velocity of ω=0.25π, 0.5π, 1.0π, 2.0π rad/s, and about its short axis with a fluid flow allow the rotation of the nanowire whose one end is contsrained to a rotational motion around x and y axis. These models were also compared with the existing analytical models. Good agreement was observed between the numerical results and analytical calculations. The FEA model is also repeated in the closed boundary to investigate the wall effects on the nanowire’s motion in liquid environment

DEVELOPMENT OF FUNCTIONAL NANOCOMPOSITE MATERIALS TOWARDS BIODEGRADABLE SOFT ROBOTICS AND FLEXIBLE ELECTRONICS

World population is continuously growing, as well as the influence we have on the ecosystem\u2019s natural equilibrium. Moreover, such growth is not homogeneous and it results in an overall increase of older people. Humanity\u2019s activity, growth and aging leads to many challenging issues to address: among them, there are the spread of suddenly and/or chronic diseases, malnutrition, resource pressure and environmental pollution. Research in the novel field of biodegradable soft robotics and electronics can help dealing with these issues. In fact, to face the aging of the population, it is necessary an improvement in rehabilitation technologies, physiological and continuous monitoring, as well as personalized care and therapy. Also in the agricultural sector, an accurate and efficient direct measure of the plants health conditions would be of help especially in the less-developed countries. But since living beings, such as humans and plants, are constituted by soft tissues that continuously change their size and shapes, today\u2019s traditional technologies, based on rigid materials, may not be able to provide an efficient interaction necessary to satisfy these needs: the mechanical mismatch is too prohibitive. Instead, soft robotic systems and devices can be designed to combine active functionalities with soft mechanical properties that can allow them to efficiently and safely interact with soft living tissues. Soft implantable biomedical devices, smart rehabilitation devices and compliant sensors for plants are all applications that can be achieved with soft technologies. The development of sophisticated autonomous soft systems needs the integration on a unique soft body or platform of many functionalities (such as mechanical actuation, energy harvesting, storage and delivery, sensing capabilities). A great research interest is recently arising on this topic, but yet not so many groups are focusing their efforts in the use of natural-derived and biodegradable raw materials. In fact, resource pressure and environmental pollution are becoming more and more critical problems. It should be completely avoided the use of in exhaustion, pollutant, toxic and non-degradable resources, such as lithium, petroleum derivatives, halogenated compounds and organic solvents. So-obtained biodegradable soft systems and devices could then be manufactured in high number and deployed in the environment to fulfil their duties without the need to recover them, since they can safely degrade in the environment. The aim of the current Ph.D. project is the use of natural-derived and biodegradable polymers and substances as building blocks for the development of smart composite materials that could operate as functional elements in a soft robotic system or device. Soft mechanical properties and electronic/ionic conductive properties are here combined together within smart nanocomposite materials. The use of supersonic cluster beam deposition (SCBD) technique enabled the fabrication of cluster-assembled Au electrodes that can partially penetrate into the surface of soft materials, providing an efficient solution to the challenge of coupling conductive metallic layers and soft deformable polymeric substrates. In this work, cellulose derivatives and poly(3-hydroxybutyrate) bioplastic are used as building blocks for the development of both underwater and in-air soft electromechanical actuators that are characterized and tested. A cellulosic matrix is blended with natural-derived ionic liquids to design and manufacture completely biodegradable supercapacitors, extremely interesting energy storage devices. Lastly, ultrathin Au electrodes are here deposited on biodegradable cellulose acetate sheets, in order to develop transparent flexible electronics as well as bidirectional resistive-type strain sensors. The results obtained in this work can be regarded as a preliminary study towards the realization of full natural-derived and biodegradable soft robotic and electronic systems and devices

NASA Tech Briefs, August 2009

Topics covered include: Aligning a Receiving Antenna Array to Reduce Interference; Collecting Ground Samples for Balloon-Borne Instruments; Tethered Pyrotechnic Apparatus for Acquiring a Ground Sample; Enhanced Video-Oculography System; Joint Carrier-Phase Synchronization and LDPC Decoding; Dual-Polarization, Sideband-Separating, Balanced Receiver for 1.5 THz Modular Battery Charge Controller; Efficient Multiplexer FPGA Block Structures Based on G4FETs; VLSI Microsystem for Rapid Bioinformatic Pattern Recognition; Low-Noise Amplifier for 100 to 180 GHz; Improved Fabrication of Ceramic Matrix Composite/Foam Core Integrated Structures; Inert Welding/Brazing Gas Filters and Dryers; Fabricating Copper Nanotubes by Electrodeposition; Reducing Aerodynamic Drag on Empty Open Cargo Vehicles; Rotary Percussive Auto-Gopher for Deep Drilling and Sampling; More About Reconfigurable Exploratory Robotic Vehicles; Thermostatic Valves Containing Silicone-Oil Actuators; Improving Heat Flux Performance of Flat Surface in Spray-Cooling Systems; Treating Fibrous Insulation to Reduce Thermal Conductivity; Silica-Aerogel Composites Opacified with La(sub0.7)Sr(sub0.3)MnO3; Cyclic Oxidation Behavior of CuCrAl Cold-Sprayed Coatings for Reusable Launch Vehicles; Ceramic Fiber Structures for Cryogenic Load-Bearing Applications; Elastomer Reinforced with Carbon Nanotubes; Biologically Inspired Purification and Dispersion of SWCNTs; A Technique for Adjusting Eigenfrequencies of WGM Resonators; Low-Pressure, Field-Ionizing Mass Spectrometer; Modifying Operating Cycles to Increase Stability in a LITS; Chamber for Simulating Martian and Terrestrial Environments; Algorithm for Detecting a Bright Spot in an Image; Extreme Programming: Maestro Style; Adaptive Behavior for Mobile Robots; Protocol for Communication Networking for Formation Flying; Planning Complex Sequences Using Compressed Representations; and Self-Supervised Learning of Terrain Traversability from Proprioceptive Sensors

Statische und dynamische Magnetfelder für die Nanopartikel-basierte zielgerichtete Wirkstofffreisetzung

Although medicine has made great progress in the last centuries and decades, it is still facing basic challenges that make doctors fail to efficiently and successfully treat the continuously emerging diseases and ailments due to ageing, industrialization, pollution and resulting biological mutations. In this context, the systemic chemotherapeutic treatment of cancer seems to be one of the most fitting examples for the wide gap between the usually followed medical approach and the theoretically optimal solution. Extrapolating from in vitro experiments and mouse models to humans, treating children as “miniaturized” adults when analyzing therapeutic effects, estimating drug doses based on relatively coarse processes like up scaling on weight, volume or area, and flooding the human body with drugs to solely achieve a minimal effect at the ailment site are just few examples for improvement needs in medical methods. One of the most promising approaches intended to bring more specificity and precision into the therapeutic toolbox is the directed delivery of drugs, already prophesized and described one hundred years ago by the German immunologist and Nobel Laureate in Medicine (1908) Paul Ehrlich (1854-1915) as the “magic bullet” principle. It is a visionary medical method in which active agents -such as drugs or antibodies- are guided within the human body and brought to bind directly and exclusively to their biological target. This approach was triggered and has been remarkably promoted by the introduction and continuous development of nano-sized medical systems since the 1950s, and is expected to experience a real breakthrough by the clinical validation of the so called “Magnetic Drug Targeting”. According to this technique, magnetically active nanoparticles are coated with a therapeutically active biomaterial and guided through external magnetic fields in the natural transport pathways of the body, then retained and concentrated at target sites where the biologically active load is set free. The delivered dose is augmented, side effects are lowered and the overall therapeutic efficiency is enhanced. Especially for cancer treatment, the magnetically guided drug delivery represents a huge potential. In fact, conventional chemotherapy methods are used systemically and succeed in best cases in delivering only a fractional amount of the drug to the target sites, while the rest is absorbed by the healthy tissue of the treated body. This is so inefficient that dose levels of about 50 to 100-fold those of conventional doses need to be administered to achieve cures of cancer cells (T. A. Connors 1995). As a result, blood filtering and trafficking organs, such as the liver, the kidneys, the spleen and most importantly the heart, are the direct victims of the highly toxic substances used in chemotherapy. Even the apparently more gentle approach of applying the maximum tolerated dose at defined intervals -in order to avoid toxicity- can unintentionally lead to a chemoresistance of the tumor (C. Damyanov 2009). These shortcomings of the chemical therapy further aggravate the fact that cancer is still the worldwide deadliest disease, with an upward trend. For instance, around 25 % of all registered death cases in the European Union are reported by the World Health Organization to be caused by tumors. Despite the development of advanced anti-cancer medicine, it still remains a difficult challenge to keep costs at an affordable level. For that reason, new and more efficient cancer treatment methods with higher success rates and lower side effects and costs are urgently needed and would help physicians cope with an ever ageing world population. In this work, we report improvements achieved in the understanding and control of the magnetically targeted drug delivery, mainly realized by the consideration of time issues and the investigation of dynamic magnetic fields. New approaches to assess the magnetic behavior of nanoparticles in suspensions as well as an advanced examination of the lung drug targeting and the mechanisms of cellular drug uptake after successful localized delivery represent the major achievements compiled in this manuscript. The registered improvements are an important contribution to the further development of the idea of directed therapies promoted by the emerging nanomedicine. This modern medicine is expected to provide techniques that can act on a cellular and even sub-cellular level, treating ailments with considerably more accuracy. Gradually, modern diagnostic and therapeutic techniques should elevate us slowly to the point where we can start thinking more in terms of real “regenerative” medicine. That means, we should be able to precisely and directly address pathologic tissues, save cells and organs, repair and heal them, rather than extinguish them.Mehr als hundert Jahre nach dem Tod von Paul Ehrlich, dem bedeutendsten deutschen Immunologen, verfolgt die "Nachwelt" noch mit großen Schritten eine seiner wichtigsten Visionen, die er während seiner Arbeiten zur Behandlung der Syphilis entwickelte: eine „Zauberkugel“ (magic bullet), die einen gegebenen krankmachenden Erreger gezielt abtöten kann. Ganz nach diesem noch -mehr denn je- aktuellen Prinzip, entwickeln Forscher heutzutage weltweit neue Methoden, um nicht nur Krankheitserreger, sondern auch befallene Gewebe, spezifisch zu behandeln. In den letzten Jahren entwickelte sich dadurch die Medizin von der konventionellen Anwendung, über die personalisierte Behandlung, wo die genetische Information eines jeden Patienten präventiv untersucht werden kann und die Ergebnisse zur Auswahl und Anpassung der Therapie-Art herangezogen werden, bis hin zur "Nanomedizin", einer neuen Ära der Arzneimittel-Konzipierung, -Synthese, -Dosierung und -Verabreichung, die Therapien auf zellulärer und sub-zellulärer Ebene ermöglichen sollte. Mediziner sind heutzutage weit entfernt von der Darstellung von Christian Friedrich Hebbel (18.03.1813 - 13.12.1863), dass "ein Arzt eine Aufgabe hat, als ob ein Mensch in einem dunklen Zimmer in einem Buche lesen sollte". Sie sind in der Lage, durch die Integration der Nanotechnologie im biomedizinischen Bereich, Gewebe und Zellen, die durchschnittliche Dimensionen von 10 µm haben, mit Nanosystemen im Submikrometer-Bereich zu adressieren und gezielt zu behandeln. In diesem Rahmen präsentiert sich das Magnetic Drug Targeting (MDT) als besonders wirksamer Therapie-Ansatz. Dabei werden Wirkstoff-beladene magnetische Nanopartikel über externe Magnetfelder im Körper geführt und an einem gegebenen Krankheitsort lokal angereichert. Die verabreichte Wirkdosis wird dadurch erhöht, Nebeneffekte minimiert. Besonders in der Krebsbekämpfung verspricht dieser Ansatz hohe Erfolgsquoten und eine Reduzierung der ohnehin enormen Chemo- und Radiotherapie-Kosten, die meistens einen bremsenden Effekt auf die Entwicklung und Verbreitung zahlreicher Behandlungsmethoden haben. An dieser Stelle sei daran erinnert, dass Krebs nach wie vor die weltweit wichtigste Todesursache ist, an der schätzungsweise 11.5 Millionen Weltbewohner im Jahre 2030 sterben werden, was einem Anstieg von 45% zum Jahre 2007 darstellt. Die zielgerichtete Arzneimittel-Applikation, zu Englisch "Directed Drug Delivery", soll hierfür Lösungen anbieten, die Tumore spezifisch angreifen und ausschalten können. Durch eine magnetische Lenkung und Anreicherung wird dieses Verfahren weiter optimiert. Die somit entstehende MDT-Methode eignet sich für Anwendungen in der Blutbahn, sowie in den Atemwegen von Patienten, mit entsprechenden Anpassungen. Entscheidend ist hierbei vor Allem das eingesetzte Magnetfeld, in Bezug auf Amplitude, Homogenität und Dynamik. In zahlreichen wissenschaftlichen Arbeiten, wurden bisher Erfolg versprechende Ergebnisse präsentiert, die überwiegend durch die Manipulation und Aufkonzentrierung von Nanopartikel-Wirkstoff-Komplexen mit statischen Magnetfeldern realisiert wurden. Eine hierzu komplementäre Betrachtung mit dynamischen Magnetfeldern wird in dieser Arbeit untersucht. Im Rahmen dieses Forschungsprojekts wurden Ansätze mit statischen und dynamischen Magnetfeldern zur Verbesserung des Magnetic Drug Targeting theoretisch überprüft, simulativ validiert und systemtechnisch umgesetzt. Nach einer ausführlichen Untersuchung der Nanopartikel-Eigenschaften, die den MDT-Effekt überhaupt ermöglichen und besonders beeinflussen, wurde der Anreicherungsprozess unter Magnetkraftwirkung modelliert und ein für Anwendungen in der Blutbahn optimiertes Magnetsystem simuliert, konstruiert und bei in-vivo-Versuchen eingesetzt. Dadurch konnte eine aktive und vor Allem reproduzierbare Retention von beladenen Nanopartikel-Komplexen in den Arterien und Venen der Rückenhaut einer Maus verzeichnet werden

Flexible and Stretchable Electronics

Flexible and stretchable electronics are receiving tremendous attention as future electronics due to their flexibility and light weight, especially as applications in wearable electronics. Flexible electronics are usually fabricated on heat sensitive flexible substrates such as plastic, fabric or even paper, while stretchable electronics are usually fabricated from an elastomeric substrate to survive large deformation in their practical application. Therefore, successful fabrication of flexible electronics needs low temperature processable novel materials and a particular processing development because traditional materials and processes are not compatible with flexible/stretchable electronics. Huge technical challenges and opportunities surround these dramatic changes from the perspective of new material design and processing, new fabrication techniques, large deformation mechanics, new application development and so on. Here, we invited talented researchers to join us in this new vital field that holds the potential to reshape our future life, by contributing their words of wisdom from their particular perspective