Membrane and Arrayed Nanofluidic Devices with High Density Aligned Carbon Nanotubes

Exceptionally high aspect ratio, smooth hydrophobic graphitic walls, and nanoscale inner diameters of carbon nanotubes (CNTs) cause the unique phenomenon of efficient transport of water and gas through these nanoscale molecular tubes. Molecular transport through the cores of CNTs is of significant interest from both fundamental and application aspects. The application of CNTs as nanofluidic channels is envisioned in many areas, ranging from desalination, carbon capture, drug delivery, DNA sequencing and translocation, protein separation, single molecule sensing, to nanofluidic transistors and diodes. A fundamental understanding of the mechanisms governing molecular transport through CNT pores is much needed and, unfortunately, still lacking, which demands further research. In this work, CNT-based smart membranes and arrayed devices are explored both as a versatile platform for fundamental studies and as exemplary devices for biosensing applications. In Chapter 3, a study of ion transport across smart, DNA-functionalized CNT membranes is reported. The diffusive transport rates of ferricyanide ions were monitored through an array of vertically aligned CNTs (VA-CNTs) functionalized with amine-modified single-stranded DNA (ssDNA) (Cy3-T15-NH2) probes. Reversible closing of CNT pores was achieved by the addition of complementary DNA (A15), gating ion transport. Our analysis suggests that pore blocking occurs due to steric hindrance at the CNT pore entrances. Chapter 4 focuses on the design and fabrication of arrayed CNT devices. Each device consists of a large number (roughly 4x105) of aligned multiwalled CNTs span a barrier separating two fluid reservoirs, enabling direct electrical chronoamperometric measurement of ion transport through the nanotubes and analyzing ion transport properties. Here we intend to demonstrate the theoretically predicted ultrahigh ion flow rate through multiplexed CNT devices that are directly electrically addressable. Compared with traditional nanopore devices, ours feature distinct advantages. The CNTs have a remarkably high aspect ratio and they can confine an entire molecule and also extend the duration of transport, which is likely to result in new translocation characteristics. Our devices have a planar design, which enable simultaneous optical and electrical probing. Results presented in this work show the potential of CNT nanofluidic devices for the fundamental studies of the nanoconfinement effects on ion transport. The developed synthesis and fabrication methods are envisioned to lead to novel biosensors based on nanofluidics, which can find a broad spectrum of significant applications such as disease diagnostics, food safety monitoring, and environmental pollution detection.1 yea

BioMEMS

As technological advancements widen the scope of applications for biomicroelectromechanical systems (BioMEMS or biomicrosystems), the field continues to have an impact on many aspects of life science operations and functionalities. Because BioMEMS research and development require the input of experts who use different technical languages and come from varying disciplines and backgrounds, scientists and students can avoid potential difficulties in communication and understanding only if they possess a skill set and understanding that enables them to work at the interface of engineering and biosciences. Keeping this duality in mind throughout, BioMEMS: Science and Engineering Perspectives supports and expedites the multidisciplinary learning involved in the development of biomicrosystems. Divided into nine chapters, it starts with a balanced introduction of biological, engineering, application, and commercialization aspects of the field. With a focus on molecules of biological interest, the book explores the building blocks of cells and viruses, as well as molecules that form the self-assembled monolayers (SAMs), linkers, and hydrogels used for making different surfaces biocompatible through functionalization. The book also discusses: Different materials and platforms used to develop biomicrosystems Various biological entities and pathogens (in ascending order of complexity) The multidisciplinary aspects of engineering bioactive surfaces Engineering perspectives, including methods of manufacturing bioactive surfaces and devices Microfluidics modeling and experimentation Device level implementation of BioMEMS concepts for different applications. Because BioMEMS is an application-driven field, the book also highlights the concepts of lab-on-a-chip (LOC) and micro total analysis system (μTAS), along with their pertinence to the emerging point-of-care (POC) and point-of-need (PON) applications

BioMEMS

As technological advancements widen the scope of applications for biomicroelectromechanical systems (BioMEMS or biomicrosystems), the field continues to have an impact on many aspects of life science operations and functionalities. Because BioMEMS research and development require the input of experts who use different technical languages and come from varying disciplines and backgrounds, scientists and students can avoid potential difficulties in communication and understanding only if they possess a skill set and understanding that enables them to work at the interface of engineering and biosciences. Keeping this duality in mind throughout, BioMEMS: Science and Engineering Perspectives supports and expedites the multidisciplinary learning involved in the development of biomicrosystems. Divided into nine chapters, it starts with a balanced introduction of biological, engineering, application, and commercialization aspects of the field. With a focus on molecules of biological interest, the book explores the building blocks of cells and viruses, as well as molecules that form the self-assembled monolayers (SAMs), linkers, and hydrogels used for making different surfaces biocompatible through functionalization. The book also discusses: Different materials and platforms used to develop biomicrosystems Various biological entities and pathogens (in ascending order of complexity) The multidisciplinary aspects of engineering bioactive surfaces Engineering perspectives, including methods of manufacturing bioactive surfaces and devices Microfluidics modeling and experimentation Device level implementation of BioMEMS concepts for different applications. Because BioMEMS is an application-driven field, the book also highlights the concepts of lab-on-a-chip (LOC) and micro total analysis system (μTAS), along with their pertinence to the emerging point-of-care (POC) and point-of-need (PON) applications

Electrochemical Capacitors for Miniaturized Self-powered Systems

Miniaturized self-powered systems with harvest-store-use architectures have been recognized as a key enabler to the internet-of-things (IoT), and further the internet-of-everything (IoE), 5G communication and tactile internet. Electrochemical capacitors (ECs), also known as supercapacitors, are promoted to be the energy storage component in such systems, because of their advantages such as an almost limitless cycle life that is ideal for the vision of “fit-and-forget” maintenance-free networks. Moreover, ECs are able to undertake tasks beyond energy storage. For example, high-frequency ECs can potentially replace the bulky electrolytic capacitors as AC line filters, with benefits in sizing down the circuitry boards and thus constructing compact systems which are pursued by the IoT technology.Bringing the IoT high-level requirements down to the device-level specifications, challenges to ECs are identified in different aspects, including device electrochemical performance, and device encapsulation/integration. Regarding the performance, challenges exist in (1) improving the energy density, (2) maximizing the operating voltage limit, (3) widening the working temperature range, (4) minimizing the self-discharge and leakage current, and (5) enhancing the frequency response property. Regarding the encapsulation and integration aspect, challenges exist in device design and fabrication. Novel encapsulation and integration EC concepts are thus appreciated to be compatible with the surface mount technology, allow for convenient adaption in the form factor and arbitrary choice of the EC materials (electrodes, electrolytes and separators). Moreover, the EC materials should be durable under the ambient conditions that occur during the encapsulation and integration processes, such as high-temperature exposure for the reflow soldering technique.The thesis research work addresses the device performance challenges. Specifically, the use of redox electrolytes is promoted for improving the energy density of ECs towards a battery-level, and at the same time keeping the capacitor-level power capability and cycling stability. With a redox-active electrolyte KBr, hybrid devices combining the features of both batteries and ECs are constructed, and a 1.9 V maximum operating voltage is achieved in the aqueous system. Furthermore, voltage- and history-dependent behaviors are revealed, reminding the complexity of hybrid systems. To explore the extreme high-temperature performance, a special measurement setup is customized and an EMImAc (1-Ethyl-3-methylimidazolium acetate) ionic liquid (IL) electrolyte is employed to enable an operation at a maximum of 150 \ub0C. It is observed that the energy and power densities at high temperatures may not be sacrificed when decreasing the operating voltage limit, therefore it is proposed that for neat IL-based ECs, a strategy of trading the voltage limit for gaining stability at extreme high-temperatures can be considered.With a graphite and carbon nanotubes hybrid material, it is demonstrated that the self-discharge and leakage current can be suppressed by employing a gel polymer electrolyte. Using the same electrode material, high-frequency ECs that are suitable for AC line filtering tasks are fabricated. The working frequency range is up to kHz with a state-of-art level areal (1.38 mF cm-2) and volumetric capacitances (345 mF cm-3), benefiting from a possible covalent bonding between graphite substrate and the CVD grown CNTs.Not limited to the above research findings, this thesis has critically reviewed and summarized the general strategies and methods to address all the identified challenges to ECs for their application in miniaturized self-powered systems