Carbon Nanotube Based Mems Energy Storage Devices
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Carbon Nanotube-based MEMS Energy Storage Devices
Carbon nanotube (CNT) forests have been utilized as electrodes in supercapacitors in this work for energy storage applications. High surface area to volume ratio, good electrical conductivity, and low contact resistance to a bottom metal electrode make CNT forests attractive as electrodes in supercapacitors. Several approaches have been investigated to improve the performances such as configurations, power and energy density of CNT-based supercapacitors, including the single layer architecture by utilizing interdigitated finger electrodes, pseudo capacitors based on electroplated nickel nanoparticles, ultra-long and densified CNT forests electrodes. Vertically aligned CNT forests have been synthesized using the thermal CVD process and their sheet and contact resistances have been characterized with four distinct methods: (1) the transfer length method (TLM), (2) the contact chain method, (3) the Kelvin method, and (4) the four point probe method. Experimental results show that CNT forests of 100μm in height and 100μm in width have a sheet resistance of about 100ohm/sq;. The specific contact resistance to a current collector is 5×10E4 ohm.μm2. Consistent results from these methods have been observed and less than 0.9% resistance deviations were measured after two months of open-air storage. In the first development stage, planar supercapacitors based on CNT forests electrodes with interdigitated finger shapes have been fabricated using a combination of Mo/Al/Fe metal stack layers to achieve dense growth of CNT with low resistance. The specific capacitances of the prototype electrodes were measured to be about 1000 times higher than those made of flat metal electrodes. Furthermore, charging/discharging experiments show over 92% energy storage efficiency and robust cycling stability. In the second development stage, CNT forests with embedded nickel nanoparticles have been used as electrodes for pseudo supercapacitors. A vacuum infiltration process is used in the electroplating process for the uniform deposition of 30-200nm in diameter nickel nanoparticles within the 80μm-high CNT forests. The measured specific capacitances are up to one order of magnitude higher than those CNT forests electrodes without nickel nanoparticles. No visual morphologic change was observed on nanoparticles after 1000 cycles of cyclic voltammetry tests. In the third development stage, ultra long CNT forests were synthesized using a water-assisted CVD process. Experimental results confirmed the capacitance increments were linearly proportion to the height increase of CNT forests with good long term stability. In the fourth development stage, a two-stage, self-aligned liquid densification process has applied on CNT forest to shrink the volume of CNT forests electrodes. By combining both mechanical bending and liquid densification, the height of CNT forest shrunk from 320μm to 21μm. Experimental results show self-aligned and continuous CNT films with preserved bottom contacts to the conductive metal layer. These densified CNT forests electrodes had similar total capacitances before and after the densification process while the volumetric specific capacitance increased from 1.07F/cm3 to 10.7F/cm3 because of the volume reductions.
Carbon Based Electronic Devices
For more than 50 years, silicon has dominated the electronics industry. However, this growth will come to an end, due to resources limitations. Thus, research developments need to focus to alternative materials, with higher performance and better functionality. Current research achievements have indicated that carbon is one of the promising candidates for its exploitation in the electronics industry. Whereas the physical properties of graphite and diamond have been investigated for many years, the potential for electronic applications of other allotropes of carbon (fullerenes, carbon nanotubes, carbon nanofibres, carbon films, carbon balls and beads, carbon fibers, etc), has only been appreciated relatively recently. Carbon-based materials offer a number of exciting possibilities for new applications of electronic devices, due to their unique thermal and electrical properties. However, the success of carbon-based electronics depends on the rapid progress of the fabrication, doping and manipulation techniques. In this Special Issue, we focus on both insights and advancements in carbon-based electronics. We will also cover various topics ranging from synthesis, functionalisation, and characterisation of carbon-based materials, for their use in electronic devices, including advanced manufacturing techniques, such as 3D printing, ink-jet printing, spray-gun technique, etc.
From MEMS to Bio-MEMS and Bio-NEMS
From MEMS to Bio-MEMS and Bio-NEMS: Manufacturing Techniques and Applications details manufacturing techniques applicable to bionanotechnology. After reviewing MEMS techniques, materials, and modeling, the author covers nanofabrication, genetically engineered proteins, artificial cells, nanochemistry, and self-assembly. He also discusses scaling laws in MEMS and NEMS, actuators, fluidics, and power and brains in miniature devices. He concludes with coverage of various MEMS and NEMS applications. Fully illustrated in color, the text contains end-of-chapter problems, worked examples, extensive references for further reading, and an extensive glossary of terms. Details the Nanotechnology, Biology, and Manufacturing Techniques Applicable to Bionanotechnology Topics include: Nonlithography manufacturing techniques with lithography-based methods Nature as an engineering guide and contrasts top-down and bottom-up approaches Packaging, assembly, and self-assembly from ICs to DNA and biological cells Selected new MEMS and NEMS processes and materials, metrology techniques, and modeling Scaling laws, actuators, power generation, and the implementation of brains in miniaturizes devices Different strategies for making micromachines smarter The transition out of the laboratory and into the marketplace The third volume in Fundamentals of Microfabrication and Nanotechnology, Third Edition, Three-Volume Set, the book discusses top-down and bottom-up manufacturing methods and explains how to use nature as a guide. It provides a better understanding of how to match different manufacturing options with a given application that students can use to identify additional killer MEMS and NEMS applications. Other volumes in the set include: Solid-State Physics, Fluidics, and Analytical Techniques in Micro- and Nanotechnology Manufacturing Techniques for Microfabrication and Nanotechnology