Chaminda Jayasinghe

Spinning Carbon Nanotube Nanothread under a Scanning Electron Microscope

Nanothread with a diameter as small as one hundred nanometers was manufactured under a scanning electron microscope. Made directly from carbon nanotubes, and inheriting their superior electrical and mechanical properties, nanothread may be the world’s smallest man-made fiber. The smallest thread that can be spun using a bench-top spinning machine is about 5 microns in diameter. Nanothread is a new material building block that can be used at the nanoscale or plied to form yarn for applications at the micro and macro scales. Preliminary electrical and mechanical properties of nanothread were measured. The resistivity of nanothread is less than 10−5 Ω∙m. The strength of nanothread is greater than 0.5 GPa. This strength was obtained from measurements using special glue that cures in an electron microscope. The glue weakened the thread, thus further work is needed to obtain more accurate measurements. Nanothread will have broad applications in enabling electrical components, circuits, sensors, and tiny machines. Yarn can be used for various macroscale applications including lightweight antennas, composites, and cables.

Study on Carbon Nano-Tube Spun Thread as Piezoresistive Sensor Element

Carbon nanotube spun threads are becoming growingly important for various technological and medical applications. Threads can be spun directly from carbon nanotube arrays using age old method of spinning. The process involves two rotations about two mutually perpendicular axes viz. spinning nanotubes into thread from array and winding the spun thread on spool. It is found that an array with properties of high uniform density, low amorphous carbon content and highly aligned nano-tubes are better spinnable. Piezoresistive property of spun thread is investigated through experiments. The change in resistivity of spun carbon nanotube thread with change in load will enable its use as force sensors. In a structural neural network system a network of sensors can pinpoint the location of damage in structure. If such network can be made of very small dimension it can detect crack initiation and crack propagation. Linearity of resistivity increase with increase in strain is observed for fine spun carbon nanotube threads. Upon unloading also this linearity is preserved with same slope.

Improved processing of carbon nanotube yarn

We compared mechanical and electrical properties of carbon nanotube (CNT) yarns formed fromfour different spinningmethods. In thesemethods, a yarn was spun fromtwo aligned CNTarrays. CNTyarns fabricated fromeachmethodwere tested quantitatively through the mechanical and electrical properties and reported.This improvement is considered to be caused by multiple factors, such as reduction of the yarn diameter, densification, water evaporation, and CNT orientation. The best electrical and mechanical property of CNT yarn was observed from the fourth spinning method where heating and tension during spinning were applied. The introduced yarn spinning methods are appropriate for continuous mass production of high strength carbon nanotube yarns with controlled diameter, strength, and electrical conductivity.

Desorption kinetics of oxygen in plasma treated SWNTs by in situ thermoelectric power measurements.

The functionalization and defect formation of SWNTs caused by isotropic plasma treatments were studied using oxygen desorption/adsorption kinetics by measuring the time dependence of the in situ thermoelectric power (TEP). It is shown that the plasma treatments result in the formation of low binding energy sites for oxygen adsorption. Raman and x-ray photoelectron spectroscopy (XPS) data are in good agreement with the results.

Responsive Biosensors for Biodegradable Magnesium Implants

A biosensor is an electronic device that measures biologically important parameters. An example is a sensor that measures the chemicals and materials released during corrosion of a biodegradable magnesium implant that impact surrounding cells, tissues and organs. A responsive biosensor is a biosensor that responds to its own measurements. An example is a sensor that measures the corrosion of an implant and automatically adjusts (slows down or speeds up) the corrosion rate. The University of Cincinnati, the University of Pittsburgh, North Carolina A&T State University, and the Hannover Medical Institute are collaborators in an NSF Engineering Research Center (ERC) for Revolutionizing Metallic Biomaterials (RBM). The center will use responsive sensors in experimental test beds to develop biodegradable magnesium implants. Our goal is to develop biodegradable implants that combine novel bioengineered materials based on magnesium alloys, miniature sensor devices that monitor and control the corrosion, and coatings that slow corrosion and release biological factors and drugs that will promote healing in surrounding tissues. Responsive biosensors will monitor what is happening at the interface between the implant and tissue to ensure that the implant is effective, biosafe, and provides appropriate strength while degrading. Corrosion behavior is a critical factor in the design of the implant. The corrosion behavior of implants will be studied using biosensors and through mathematical modeling. Design guidelines will be developed to predict the degradation rate of implants, and to predict and further study toxicity arising from corrosion products (i.e., Mg ion concentrations, pH levels, and hydrogen gas evolution). Knowing the corrosion rate will allow estimations to be made of implant strength and toxicity risk throughout the degradation process.Copyright

A new class of lightweight, multifunctional material for electromagnetic compatibility

A new class of lightweight, multifunctional material has been developed for electromagnetic compatibility. This material, branded VeeloSTRIKE, was designed to provide lightning strike protection, broadband shielding, and electrical uniformity in carbon fiber reinforced polymer composites. Aerospace and defense prime contractors and integrators are evaluating this proprietary carbon nanotube blended material to improve hardening against electromagnetic environment effects, such as lightning strike protection, electromagnetic pulse, high intensity radiated fields, electromagnetic interference, and electrostatic discharge. This material is targeted as an alternative to heavy metals, particularly expanded metal foils, woven mesh, and filled polymers. VeeloSTRIKE is between one-third and one-half the weight of tradition metallic solutions while providing enhanced high-frequency shielding effectiveness and protecting against Zone 1A lightning.

Carbon nanotube responsive materials and applications

Carbon nanotubes (CNTs) have attracted a lot of interest in the past 20 years. Superior mechanical, …