Browsing by Author "Pasquali, Matteo"
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Item 4-Field Galerkin/least-squares method for polymer flows(2004) Wang, Xiruo; Pasquali, MatteoIn this thesis, a new finite element method, 4-field Galerkin/Least-Squares method, is presented to solve viscoelastic flow problems. The 4-field GLS naturally includes the SUPG and PSPG terms to stabilize the oscillations caused by advection-dominated terms. In addition, it introduces a new variable L = ∇v, so that the second order derivative of v is avoided, and the basis functions can be chosen as piecewise linear functions. This feature substantially enlarges the space of the basis and weighting functions. The Galerkin terms in this formulation guarantee that the traction term n·T appears naturally by integration by part, which serves as an important boundary condition for free surface flow. Moreover, the 4-field GLS successfully circumvents the LBB condition on velocity and conformation fields. The 4-field GLS is tested with a carefully defined set of benchmark problems for both Newtonian and non-Newtonian fluid. It is found to be robust, accurate and efficient.Item Advances in Carbon Nanotechnology: Non-Equilibrium Graphene Synthesis and the Control of Cell Signaling with Molecular Machines(2023-08-11) Beckham, Jacob Lee; Tour, James; Pasquali, MatteoCarbon, known as the "element of life," has long fascinated researchers due to its exceptional versatility as a molecular building block. With its ability to form a wide range of molecular structures and exhibit diverse bonding configurations, carbon has become the cornerstone of countless organic compounds. In recent years, this inherent versatility has taken on a new dimension with the emergence of carbon nanomaterials, including carbon nanotubes, graphene, and, indeed, even buckminsterfullerenes. These materials hold immense promise for the advancement of both science and industry. This thesis presents several major advances in the field of carbon nanotechnology. First, various investigations of non-equilibrium graphene synthesis techniques are discussed. Second, the use of carbon-based molecular nanomotors to control cell signaling is explored. In the first several chapters, explorations using different non-equilibrium synthesis techniques to generate graphene are presented. Chapter 1 explores the conversion of positive photoresist into laser-induced graphene, demonstrating that a combination of lasing and photolithography allows the patterning of graphene at high resolution. Chapter 2 presents machine learning models trained to predict the extent of crystallization in beds of amorphous carbon treated with an electrothermal discharge. This work comprised a major thrust in our lab’s research program on flash Joule heating and revealed several key factors for the design of Joule heating reactors. This work also presented software programs capable of learning to synthesize graphene from scrap rubber tires with no human oversight using Bayesian meta-learning. Chapter 3 represents a pivot in my PhD where I began exploring the biomedical applications of carbon nanomaterials. In the Tour lab, we explore the use of carbon-based molecular motors for various applications in biology. These molecular motors convert incident photons into mechanical work through a series of photochemical and thermal steps. Our previous work has shown that the actuation of fast molecular motors causes the permeabilization of lipid bilayers. Chapter 3 is a perspective discussing the potential applications of these motors, laying out foundational standards for the literature. This chapter discusses how to differentiate the light-driven effects of molecular actuation and potential confounding factors, including photothermal and photodynamic effects. Chapter 4 then demonstrates the use of these molecular motors for the treatment of fungal infections. This work involved extensive microscopy and fundamental studies showing how our motors are processed by eukaryotes, and what that might imply for their basic mechanism-of-action. Chapter 5 explores the use of these molecular motors to control cell signaling. When they are mechanically perturbed, cells participate in mechanosensitive signaling phenomena known as intercellular calcium waves. Thirty years ago, cell biologists used to study calcium waves initiated by poking cells with a micropipette. My work showed that the same responses could be achieved using a fast, unidirectional molecular motor. This work represents the first demonstration that a cell signaling cascade could be initiated by the mechanical force administered by a small molecule, opening the door for the design of new drugs that work based on mechanical, rather than chemical, forces. Chapter 6 explores the dependence of motor performance on the functionalization chemistry used in the motor. Our findings indicate that surface charge and polarity are critical factors that drive motor effectiveness for killing bacteria, killing fungi, and initiating calcium waves. We found substantial overlap in motor performance across all three tasks. Finally, Chapter 7 explores the use of molecular motors to control endocrine signaling. This chapter shows that light-activated motors can potentiate the release of insulin from pancreatic beta cells through the modulation of intracellular calcium, a finding with substantial implications for the design of new drugs to treat diabetes.Item Adverse Effect of PTFE Stir Bars on the Covalent Functionalization of Carbon and Boron Nitride Nanotubes Using Billups–Birch Reduction Conditions(American Chemical Society, 2019) de los Reyes, Carlos A.; Smith McWilliams, Ashleigh D.; Hernández, Katharyn; Walz-Mitra, Kendahl L.; Ergülen, Selin; Pasquali, Matteo; Martí, Angel A.The functionalization of nanomaterials has long been studied as a way to manipulate and tailor their properties to a desired application. Of the various methods available, the Billups–Birch reduction has become an important and widely used reaction for the functionalization of carbon nanotubes (CNTs) and, more recently, boron nitride nanotubes. However, an easily overlooked source of error when using highly reductive conditions is the utilization of poly(tetrafluoroethylene) (PTFE) stir bars. In this work, we studied the effects of using this kind of stir bar versus using a glass stir bar by measuring the resulting degree of functionalization with 1-bromododecane. Thermogravimetric analysis studies alone could deceive one into thinking that reactions stirred with PTFE stir bars are highly functionalized; however, the utilization of spectroscopic techniques, such as Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, tells otherwise. Furthermore, in the case of CNTs, we determined that using Raman spectroscopy alone for analysis is not sufficient to demonstrate successful chemical modification.Item An Investigation of Carbon-based Nanomaterials for Efficient Energy Production and Delivery(2016-01-28) Gangoli, Varun Shenoy; Wong, Michael S.; Pasquali, Matteo; Barron, Andrew R; Adams, Wade; Hauge, Robert HCarbon-based nanomaterials have been demonstrated to have different potential applications in the energy industry. However, there are challenges in the realization of these applications. Chirality of single wall carbon nanotubes (SWCNTs) defines their electronic properties, and obtaining an ensemble of SWCNTs of the same chirality has been a problem studied for over two decades with no clear solution yet. Other carbon-based nanomaterials, such as carbon black aggregates, are hydrophobic in nature and potential applications in the oil and gas industry require their dispersal in an aqueous solvent. Another application in the oil and gas industry is enhanced oil recovery (EOR), and here there is a need for an inexpensive, stable, and efficient surfactant compared to currently used industrial solutions. The challenge of producing SWCNTs of the same chirality is studied using two approaches- separation after synthesis of SWCNTs of mixed chiralities, and chemical control over chirality of as-synthesized SWCNTs. Agarose gel-based affinity chromatography was used as a means towards highly semiconductor- enriched SWCNTs using a family of nonionic surfactants. UV-vis-NIR spectroscopy, Raman spectroscopy and photoluminescence spectroscopy was used to quantify the separation efficiency of the metal- and semiconductor-enriched SWCNTs. This process is an improvement over other chromatography-based techniques at the time in that the nonionic surfactants used are less expensive, enable a higher purity of semiconductor SWCNTs (>95%) and decompose fully by simply heating in air thus leaving behind pristine SWCNTs. The second approach was based on using catalyst dopants to preferentially synthesize SWCNTs of a particular chirality at the expense of SWCNTs of other chiralities. Heterogeneous catalysis combined with the screw dislocation theory of SWCNT growth provided the background for this work, and both selenium and phosphorus were identified as chemical dopants for iron catalysts. Both selenium and phosphorus were demonstrated to have a direct effect on the average number density and length of SWCNTs, and selenium also was shown to have a direct control over the growth rate of SWCNTs. This, combined with some preliminary spectroscopy results, suggest chiral control over the carbon nanotubes. Collaborative work on phase transfer of hydrophobic carbon-based nanomaterials into aqueous solvents for applications including saturated oil residual (SOR) detection and quantification in underground reservoirs helped recognize the potential of hydrophobically modified polymers as surfactants for EOR. Polystyrene sulfonate was chosen as the polymer of study owing to ease of availability, low cost of the precursor material and aromatic sulfonates already being studied for EOR. Controlled desulfonation of PSS was achieved by rapid heating of an aqueous solution of PSS in a microwave reactor under acidic conditions, with the reactant temperature and pH having a strong effect on the degree of desulfonation of the product ranging from 4.9% (as-obtained PSS) to 40%. Dynamic light scattering of the desulfonated PSS (termed PDS) in brine showed good stability of the polymer aggregates at temperatures as high as 150 ºC, and tensiometry with aromatic oils such as toluene and aliphatic oils such as Isopar L showed good surface activity with interfacial tension going as low as 10-2 mN/m. Breakthrough experiments with sand packed columns at the lab scale, and core flooding at an independent facility confirmed good propagation of PDS through materials such as Berea sandstone, with minimal plugging and adsorption losses.Item Anisotropic Noble Metal Nanomaterials for Analytical Surface Enhanced Raman Spectroscopy(2014-09-03) Payne, Courtney Michelle; Hafner, Jason H; Colvin, Vicki L; Pasquali, MatteoNoble metal mesoscale and nanoscale materials exhibit unique optical properties that are of interest to a wide variety of fields including sensing, imaging, biomedicine, and catalysis. The properties of the nanomaterial are strongly dependent on the size, morphology, composition, and local molecular environment of the material, all of which can be controlled by material design and synthesis. A novel nanomaterial referred to as a gold nanobelt was synthesized and characterized. Gold nanobelts synthesized in cetyltrimethylammonium bromide and sodium dodecylsulfate and with sub-100 nm rectangular cross sections were found to exhibit a strong transverse plasmon peak at visible wavelengths. Unlike larger diameter silver nanowires, these nanobelts exhibit sharp, tunable plasmon resonances similar to those of nanoparticles. The gold nanobelt crystal structure contains a mixture of face centered cubic and hexagonally close packed lattice phases that can be isolated and examined individually due to the unique nanobelt size and shape. The nanobelt synthesis is very sensitive to temperature which is likely due to the transition of the surfactant solution from wormlike micelles to spherical micelles. The electromagnetic field enhancing properties of gold nanobelts, silver nanowires, gold microplates, and gold nanorods were used to fabricate platforms for analytical surface enhanced Raman spectroscopy. Gold nanobelts and silver nanowires were deposited on glass substrates and when used alone or in combination with a gold microplate demonstrate surface enhancing capabilities. A thin film of gold nanorods was shown to be easily modifiable and provide surface enhanced Raman spectra of the local chemical environment.Item Biocompatible Carbon Nanotube–Chitosan Scaffold Matching the Electrical Conductivity of the Heart(American Chemical Society, 2014) Pok, Seokwon; Vitale, Flavia; Eichmann, Shannon L.; Benavides, Omar M.; Pasquali, Matteo; Jacot, Jeffrey G.; The Smalley Institute for Nanoscale Science & TechnologyThe major limitation of current engineered myocardial patches for the repair of heart defects is that insulating polymeric scaffold walls hinder the transfer of electrical signals between cardiomyocytes. This loss in signal transduction results in arrhythmias when the scaffolds are implanted. We report that small, subtoxic concentrations of single-walled carbon nanotubes, on the order of tens of parts per million, incorporated in a gelatin–chitosan hydrogel act as electrical nanobridges between cardiomyocytes, resulting in enhanced electrical coupling, synchronous beating, and cardiomyocyte function. These engineered tissues achieve excitation conduction velocities similar to native myocardial tissue (22 ± 9 cm/s) and could function as a full-thickness patch for several cardiovascular defect repair procedures, such as right ventricular outflow track repair for Tetralogy of Fallot, atrial and ventricular septal defect repair, and other cardiac defects, without the risk of inducing cardiac arrhythmias.Item Brownian dynamics simulations of single-wall carbon nanotube separation by type using dielectrophoresis(2008) Mendes, Manuel Joao de Moura Dias; Pasquali, MatteoWe theoretically investigate the separation of individualized metallic and semiconducting single-wall carbon nanotubes (SWNT) in a dielectrophoretic (DEP) flow device. The SWNTs motion is simulated by a Brownian Dynamics (BD) algorithm which includes the translational and rotational effects of hydrodynamic, Brownian, dielectrophoretic, and electrophoretic forces. The device geometry is chosen to be a coaxial cylinder, because it yields effective flow throughput, the DEP and flow fields are orthogonal to each other, and all the fields can be described analytically everywhere. We construct a flow-DEP phase map, showing different regimes depending on the relative magnitudes of the forces in play. The BD code is combined with an optimization algorithm that searches for the conditions which maximize the separation performance. The optimization results show that a 99% sorting performance can be achieved with typical SWNT parameters by operating in a region of the phase map where the metallic SWNTs completely orient with the field, whereas the semiconducting SWNTs partially flow align.Item Carbon Nanomaterials for Fibers, Photonics and Composites(2014-04-21) Xiang, Changsheng; Tour, James M.; Pasquali, Matteo; Marti, Angel A.This thesis investigates various carbon nanomaterials from the basic synthesis to the characterizations and applications in fibers, photonics and composites. The carbon nanomaterials we studied include graphene, graphene oxide, graphene nanoribbons, functionalized graphene nanoribbons, graphene oxide nanoribbons, graphene quantum dots and carbon nanotubes. With all these chemical approaches, these carbon nanomaterials’ mechanical, electrical, photonic and gas barrier properties were carefully studied and demonstrated.Item Carbon Nanotube Characterization and Processing{Structure{Property Relationships of Solution Spun Fibers for Electronic Clothing(2021-07-26) Taylor, Lauren Whitney; Pasquali, MatteoCarbon nanotubes (CNTs) have excellent mechanical strength, thermal conductivity, and electrical conductivity. These properties make them particularly interesting for high performance fiber applications such as lightweight cables and wires, soft biological implants, next generation ballistic protection, and wearable electronics. Initial efforts to develop strong and conductive CNT fibers were slow due to limited CNT production and lack of a suitable solvent due to the strong van der Waals forces between CNTs. However, significant progress in CNT fiber production came from the development of gram-quantity synthesis from the high pressure carbon monoxide (HiPCO) growth process and demonstration of CNT fiber spinning with superacid solvents. Since these developments in the early 2000’s, tensile strength and electrical conductivity of CNT fibers have increased on average ∼20% per year. Research conducted in this thesis has continued this trend and produced CNT fibers with a tensile strength of 4.2 GPa and an electrical conductivity of10.9 MS/m. These properties are now competitive with high strength fibers such as carbon fiber and aramid fibers as well as metal conductors where weight savings, flexibility, or thermal conductivity are important parameters are important parameters. To improve CNT fiber performance, this thesis studied the purification of CNTs for improved solubility in chlorosulfonic (CSA), and the effect of CNT characteristics on fiber performance. This work demonstrates that CNTs with fewer impurities produce fiber with higher electrical conductivity. However, more intense purification (furnace oxidation) decreases the aspect ratio (length of the CNT/diameter of the CNT) which decreases both tensile strength and conductivity. Therefore, purification conditions must be carefully considered to optimize fiber properties. Furthermore, it was found that lower CNT concentration in the spin dope increased tensile strength of CNT fibers. This enhancement in strength is believed to be the result of improved CNT bundle structure within the fiber. Additional improvements in strength and electrical conductivity were also achieved by decreasing the angle of the inlet cone of the spinneret. This result suggests that fiber properties could be further improved by increasing the path length of the spinneret to allow for additional stress relaxation of the solution before coagulation. Finally, this thesis demonstrates that CNT fibers can used as wearable, textile electrodes. CNT fibers were plyed into thread and sewn with a standard sewing machine into textiles to form soft electrodes. These electrodes were able to obtain high quality electrocardiograms (EKGs) on par with commercial wet electrodes. Furthermore, we show that CNT fiber can also be used as transmission lines to carry signal from the recording site to standard electronic components. These results demonstrate that CNT fiber is the ideal material for wearable electronics because it is conductive, soft, washable, and easy to integrate into clothing.Item Carbon Nanotube Characterization and Processing{Structure{Property Relationships of Solution Spun Fibers for Electronic Clothing(2021-07-26) Taylor, Lauren Whitney; Pasquali, MatteoCarbon nanotubes (CNTs) have excellent mechanical strength, thermal conductivity, and electrical conductivity. These properties make them particularly interesting for high performance fiber applications such as lightweight cables and wires, soft biological implants, next generation ballistic protection, and wearable electronics. Initial efforts to develop strong and conductive CNT fibers were slow due to limited CNT production and lack of a suitable solvent due to the strong van der Waals forces between CNTs. However, significant progress in CNT fiber production came from the development of gram-quantity synthesis from the high pressure carbon monoxide (HiPCO) growth process and demonstration of CNT fiber spinning with superacid solvents. Since these developments in the early 2000’s, tensile strength and electrical conductivity of CNT fibers have increased on average ∼20% per year. Research conducted in this thesis has continued this trend and produced CNT fibers with a tensile strength of 4.2 GPa and an electrical conductivity of10.9 MS/m. These properties are now competitive with high strength fibers such as carbon fiber and aramid fibers as well as metal conductors where weight savings, flexibility, or thermal conductivity are important parameters are important parameters. To improve CNT fiber performance, this thesis studied the purification of CNTs for improved solubility in chlorosulfonic (CSA), and the effect of CNT characteristics on fiber performance. This work demonstrates that CNTs with fewer impurities produce fiber with higher electrical conductivity. However, more intense purification (furnace oxidation) decreases the aspect ratio (length of the CNT/diameter of the CNT) which decreases both tensile strength and conductivity. Therefore, purification conditions must be carefully considered to optimize fiber properties. Furthermore, it was found that lower CNT concentration in the spin dope increased tensile strength of CNT fibers. This enhancement in strength is believed to be the result of improved CNT bundle structure within the fiber. Additional improvements in strength and electrical conductivity were also achieved by decreasing the angle of the inlet cone of the spinneret. This result suggests that fiber properties could be further improved by increasing the path length of the spinneret to allow for additional stress relaxation of the solution before coagulation. Finally, this thesis demonstrates that CNT fibers can used as wearable, textile electrodes. CNT fibers were plyed into thread and sewn with a standard sewing machine into textiles to form soft electrodes. These electrodes were able to obtain high quality electrocardiograms (EKGs) on par with commercial wet electrodes. Furthermore, we show that CNT fiber can also be used as transmission lines to carry signal from the recording site to standard electronic components. These results demonstrate that CNT fiber is the ideal material for wearable electronics because it is conductive, soft, washable, and easy to integrate into clothing.Item Carbon Nanotube Characterization and Processing{Structure{Property Relationships of Solution Spun Fibers for Electronic Clothing(2021-07-26) Taylor, Lauren Whitney; Pasquali, MatteoCarbon nanotubes (CNTs) have excellent mechanical strength, thermal conductivity, and electrical conductivity. These properties make them particularly interesting for high performance fiber applications such as lightweight cables and wires, soft biological implants, next generation ballistic protection, and wearable electronics. Initial efforts to develop strong and conductive CNT fibers were slow due to limited CNT production and lack of a suitable solvent due to the strong van der Waals forces between CNTs. However, significant progress in CNT fiber production came from the development of gram-quantity synthesis from the high pressure carbon monoxide (HiPCO) growth process and demonstration of CNT fiber spinning with superacid solvents. Since these developments in the early 2000’s, tensile strength and electrical conductivity of CNT fibers have increased on average ∼20% per year. Research conducted in this thesis has continued this trend and produced CNT fibers with a tensile strength of 4.2 GPa and an electrical conductivity of10.9 MS/m. These properties are now competitive with high strength fibers such as carbon fiber and aramid fibers as well as metal conductors where weight savings, flexibility, or thermal conductivity are important parameters are important parameters. To improve CNT fiber performance, this thesis studied the purification of CNTs for improved solubility in chlorosulfonic (CSA), and the effect of CNT characteristics on fiber performance. This work demonstrates that CNTs with fewer impurities produce fiber with higher electrical conductivity. However, more intense purification (furnace oxidation) decreases the aspect ratio (length of the CNT/diameter of the CNT) which decreases both tensile strength and conductivity. Therefore, purification conditions must be carefully considered to optimize fiber properties. Furthermore, it was found that lower CNT concentration in the spin dope increased tensile strength of CNT fibers. This enhancement in strength is believed to be the result of improved CNT bundle structure within the fiber. Additional improvements in strength and electrical conductivity were also achieved by decreasing the angle of the inlet cone of the spinneret. This result suggests that fiber properties could be further improved by increasing the path length of the spinneret to allow for additional stress relaxation of the solution before coagulation. Finally, this thesis demonstrates that CNT fibers can used as wearable, textile electrodes. CNT fibers were plyed into thread and sewn with a standard sewing machine into textiles to form soft electrodes. These electrodes were able to obtain high quality electrocardiograms (EKGs) on par with commercial wet electrodes. Furthermore, we show that CNT fiber can also be used as transmission lines to carry signal from the recording site to standard electronic components. These results demonstrate that CNT fiber is the ideal material for wearable electronics because it is conductive, soft, washable, and easy to integrate into clothing.Item Carbon Nanotube Characterization and Processing{Structure{Property Relationships of Solution Spun Fibers for Electronic Clothing(2021-07-26) Taylor, Lauren Whitney; Pasquali, MatteoCarbon nanotubes (CNTs) have excellent mechanical strength, thermal conductivity, and electrical conductivity. These properties make them particularly interesting for high performance fiber applications such as lightweight cables and wires, soft biological implants, next generation ballistic protection, and wearable electronics. Initial efforts to develop strong and conductive CNT fibers were slow due to limited CNT production and lack of a suitable solvent due to the strong van der Waals forces between CNTs. However, significant progress in CNT fiber production came from the development of gram-quantity synthesis from the high pressure carbon monoxide (HiPCO) growth process and demonstration of CNT fiber spinning with superacid solvents. Since these developments in the early 2000’s, tensile strength and electrical conductivity of CNT fibers have increased on average ∼20% per year. Research conducted in this thesis has continued this trend and produced CNT fibers with a tensile strength of 4.2 GPa and an electrical conductivity of10.9 MS/m. These properties are now competitive with high strength fibers such as carbon fiber and aramid fibers as well as metal conductors where weight savings, flexibility, or thermal conductivity are important parameters are important parameters. To improve CNT fiber performance, this thesis studied the purification of CNTs for improved solubility in chlorosulfonic (CSA), and the effect of CNT characteristics on fiber performance. This work demonstrates that CNTs with fewer impurities produce fiber with higher electrical conductivity. However, more intense purification (furnace oxidation) decreases the aspect ratio (length of the CNT/diameter of the CNT) which decreases both tensile strength and conductivity. Therefore, purification conditions must be carefully considered to optimize fiber properties. Furthermore, it was found that lower CNT concentration in the spin dope increased tensile strength of CNT fibers. This enhancement in strength is believed to be the result of improved CNT bundle structure within the fiber. Additional improvements in strength and electrical conductivity were also achieved by decreasing the angle of the inlet cone of the spinneret. This result suggests that fiber properties could be further improved by increasing the path length of the spinneret to allow for additional stress relaxation of the solution before coagulation. Finally, this thesis demonstrates that CNT fibers can used as wearable, textile electrodes. CNT fibers were plyed into thread and sewn with a standard sewing machine into textiles to form soft electrodes. These electrodes were able to obtain high quality electrocardiograms (EKGs) on par with commercial wet electrodes. Furthermore, we show that CNT fiber can also be used as transmission lines to carry signal from the recording site to standard electronic components. These results demonstrate that CNT fiber is the ideal material for wearable electronics because it is conductive, soft, washable, and easy to integrate into clothing.Item Carbon Nanotube Characterization and Processing{Structure{Property Relationships of Solution Spun Fibers for Electronic Clothing(2021-07-26) Taylor, Lauren Whitney; Pasquali, MatteoCarbon nanotubes (CNTs) have excellent mechanical strength, thermal conductivity, and electrical conductivity. These properties make them particularly interesting for high performance fiber applications such as lightweight cables and wires, soft biological implants, next generation ballistic protection, and wearable electronics. Initial efforts to develop strong and conductive CNT fibers were slow due to limited CNT production and lack of a suitable solvent due to the strong van der Waals forces between CNTs. However, significant progress in CNT fiber production came from the development of gram-quantity synthesis from the high pressure carbon monoxide (HiPCO) growth process and demonstration of CNT fiber spinning with superacid solvents. Since these developments in the early 2000’s, tensile strength and electrical conductivity of CNT fibers have increased on average ∼20% per year. Research conducted in this thesis has continued this trend and produced CNT fibers with a tensile strength of 4.2 GPa and an electrical conductivity of10.9 MS/m. These properties are now competitive with high strength fibers such as carbon fiber and aramid fibers as well as metal conductors where weight savings, flexibility, or thermal conductivity are important parameters are important parameters. To improve CNT fiber performance, this thesis studied the purification of CNTs for improved solubility in chlorosulfonic (CSA), and the effect of CNT characteristics on fiber performance. This work demonstrates that CNTs with fewer impurities produce fiber with higher electrical conductivity. However, more intense purification (furnace oxidation) decreases the aspect ratio (length of the CNT/diameter of the CNT) which decreases both tensile strength and conductivity. Therefore, purification conditions must be carefully considered to optimize fiber properties. Furthermore, it was found that lower CNT concentration in the spin dope increased tensile strength of CNT fibers. This enhancement in strength is believed to be the result of improved CNT bundle structure within the fiber. Additional improvements in strength and electrical conductivity were also achieved by decreasing the angle of the inlet cone of the spinneret. This result suggests that fiber properties could be further improved by increasing the path length of the spinneret to allow for additional stress relaxation of the solution before coagulation. Finally, this thesis demonstrates that CNT fibers can used as wearable, textile electrodes. CNT fibers were plyed into thread and sewn with a standard sewing machine into textiles to form soft electrodes. These electrodes were able to obtain high quality electrocardiograms (EKGs) on par with commercial wet electrodes. Furthermore, we show that CNT fiber can also be used as transmission lines to carry signal from the recording site to standard electronic components. These results demonstrate that CNT fiber is the ideal material for wearable electronics because it is conductive, soft, washable, and easy to integrate into clothing.Item Carbon Nanotube Characterization and Processing{Structure{Property Relationships of Solution Spun Fibers for Electronic Clothing(2021-07-26) Taylor, Lauren Whitney; Pasquali, MatteoCarbon nanotubes (CNTs) have excellent mechanical strength, thermal conductivity, and electrical conductivity. These properties make them particularly interesting for high performance fiber applications such as lightweight cables and wires, soft biological implants, next generation ballistic protection, and wearable electronics. Initial efforts to develop strong and conductive CNT fibers were slow due to limited CNT production and lack of a suitable solvent due to the strong van der Waals forces between CNTs. However, significant progress in CNT fiber production came from the development of gram-quantity synthesis from the high pressure carbon monoxide (HiPCO) growth process and demonstration of CNT fiber spinning with superacid solvents. Since these developments in the early 2000’s, tensile strength and electrical conductivity of CNT fibers have increased on average ∼20% per year. Research conducted in this thesis has continued this trend and produced CNT fibers with a tensile strength of 4.2 GPa and an electrical conductivity of10.9 MS/m. These properties are now competitive with high strength fibers such as carbon fiber and aramid fibers as well as metal conductors where weight savings, flexibility, or thermal conductivity are important parameters are important parameters. To improve CNT fiber performance, this thesis studied the purification of CNTs for improved solubility in chlorosulfonic (CSA), and the effect of CNT characteristics on fiber performance. This work demonstrates that CNTs with fewer impurities produce fiber with higher electrical conductivity. However, more intense purification (furnace oxidation) decreases the aspect ratio (length of the CNT/diameter of the CNT) which decreases both tensile strength and conductivity. Therefore, purification conditions must be carefully considered to optimize fiber properties. Furthermore, it was found that lower CNT concentration in the spin dope increased tensile strength of CNT fibers. This enhancement in strength is believed to be the result of improved CNT bundle structure within the fiber. Additional improvements in strength and electrical conductivity were also achieved by decreasing the angle of the inlet cone of the spinneret. This result suggests that fiber properties could be further improved by increasing the path length of the spinneret to allow for additional stress relaxation of the solution before coagulation. Finally, this thesis demonstrates that CNT fibers can used as wearable, textile electrodes. CNT fibers were plyed into thread and sewn with a standard sewing machine into textiles to form soft electrodes. These electrodes were able to obtain high quality electrocardiograms (EKGs) on par with commercial wet electrodes. Furthermore, we show that CNT fiber can also be used as transmission lines to carry signal from the recording site to standard electronic components. These results demonstrate that CNT fiber is the ideal material for wearable electronics because it is conductive, soft, washable, and easy to integrate into clothing.Item Carbon nanotube coating composition(2018-07-31) Kibe, Ryuta; Yamamoto, Takayuki; Maillaud, Laurent; Headrick, Robert James; Mirri, Francesca; Pasquali, Matteo; Rice University; Nitto Denko Corporation; United States Patent and Trademark OfficeThe present invention relates to a composition comprising carbon nanotubes and a surfactant for forming a thin film on a substrate, and a method of manufacturing a thin film on a substrate by using an aqueous dispersion of the composition comprising carbon nanotubes and a surfactant.Item Carbon Nanotube Fiber Microelectrode Arrays for Neural Recording and Stimulation Applications(2021-08-16) Pamulapati, Sushma Sri; Pasquali, MatteoImplantable neural interfaces that can simultaneously record and perturb the neuronal circuitry with neuron scale precision have profound implications in neuroscience and medicine. They hold great potential for the diagnosis and treatment of several neurological disorders such as Parkinson's disease and epilepsy. In addition, they play a crucial role in the development of neuroprosthetics and brain-computer interface (BCI) technologies that can restore functionality in patients with nervous system impairments. Despite the promise of such neuron-scale interfaces, most of the neural electrode technologies developed to date are incapable of providing simultaneous multi-channel neural recording in conjunction with micro stimulation desired for the above stated applications [59]. For instance, metal electrodes suffer limited performance in providing stable neuronal scale recording and micro stimulation because of their poor electrochemical and mechanical properties. Carbon nanotube (CNT) fiber is a novel material with a unique combination of extraordinary electrical, thermal, and mechanical properties like CNTs, their microscopic counterparts [6]. Recent studies show CNT fibers (CNTfs) as the ideal candidate material for the development of safe, effective, stable, and multifunctional neural microelectrodes without the need for any additional surface modification [78, 143, 144, 165]. This dissertation focused on developing a scaled-up high density, CNTf microelectrode array for simultaneous recording and micro-stimulation. The thesis has two portions. In the first, we present a parylene-C insulation scheme for CNTf electrodes, the first step in CNTf -based electrode development. The integrity of parylene-C coated CNTf electrodes was evaluated using modified leakage current, electron microscopy, bending stiffness, and in vitro electrochemical analysis under normal and H2O2 aging conditions at different temperatures. We demonstrated that the parylene-C alone scheme offers high conformal, flexible, minimal leakage current, and stable long-term insulation performance and is a better insulation strategy for CNTf electrodes. In the second part of this thesis, we developed and optimized micro fabrication and assembly techniques to successfully fabricate multi-channel parylene-C coated CNTf microelectrode arrays (n=8/16/32). The novel arrays demonstrate one of the lowest electrode channel impedance, high charge storage injection capacity to the metal and state-of-the-art neural electrode materials in vitro. In the final portion, we validated the implantation strategy and recording function of the developed arrays to metal electrodes using acute in vivo studies in rat models. The combination of the low impedance, better charge transfer properties, and the initial in vivo performance of the developed CNTf electrode arrays suggest they are a promising technology for neural recording and stimulation applications.Item Carbon nanotube fiber terahertz polarizer(AIP Publishing, 2016) Zubair, Ahmed; Tsentalovich, Dmitri E.; Young, Colin C.; Heimbeck, Martin S.; Everitt, Henry O.; Pasquali, Matteo; Kono, JunichiroConventional, commercially available terahertz (THz) polarizers are made of uniformly and precisely spaced metallic wires. They are fragile and expensive, with performance characteristics highly reliant on wire diameters and spacings. Here, we report a simple and highly error-tolerant method for fabricating a freestanding THz polarizer with nearly ideal performance, reliant on the intrinsically one-dimensional character of conduction electrons in well-aligned carbon nanotubes(CNTs). The polarizer was constructed on a mechanical frame over which we manually wound acid-doped CNT fibers with ultrahigh electrical conductivity. We demonstrated that the polarizer has an extinction ratio of ∼−30 dB with a low insertion loss (<0.5 dB) throughout a frequency range of 0.2–1.1 THz. In addition, we used a THzellipsometer to measure the Müller matrix of the CNT-fiber polarizer and found comparable attenuation to a commercial metallic wire-grid polarizer. Furthermore, based on the classical theory of light transmission through an array of metallic wires, we demonstrated the most striking difference between the CNT-fiber and metallic wire-grid polarizers: the latter fails to work in the zero-spacing limit, where it acts as a simple mirror, while the former continues to work as an excellent polarizer even in that limit due to the one-dimensional conductivity of individual CNTs.Item Carbon Nanotube Fibers and Films as Bioelectronic Interfaces(2020-04-24) Yan, Stephen; Pasquali, Matteo; Robinson, Jacob TCarbon nanotubes (CNTs) have generated substantial research interests since their discovery in 1991. Individual CNTs possess exceptional mechanical (1000x strength of steel), electrical (almost 2x electrical conductivity of copper), and thermal (almost 2x thermal conductivity of diamond) properties, all at a fraction of the weight. As a result of these outstanding properties, CNTs are ideal candidates in applications such as sensors, energy storage and conversion, batteries, touch screen displays, field emitters, super capacitors, aerospace, wearables, biosensors, nanomedicine, and novel biomaterials. Early CNT applications use CNTs as individual molecules, coatings, or part of composites. With advancements in CNT processing, researchers have been able to fabricate CNTs into macroscopic 1D, 2D, and 3D objects with outstanding properties, such as CNT fibers (CNTFs), films, and foams. This thesis focuses on the biomedical applications of two such CNT macrostructures – CNTFs and CNT films. First, this thesis demonstrates in vivo restoration of myocardial conduction with CNTFs. Impaired myocardial conduction is the underlying mechanism for re-entrant arrhythmias. A restorative therapy had remained elusive due to the lack of biocompatible materials that restore myocardial conduction. CNTFs are uniquely suited to fill this need because they combine the mechanical properties of soft sutures with the conductive properties of metals. Here, by showing that CNTFs sewn across the mitral valve can create or restore conduction across anatomical barriers, we demonstrate CNTF to be a potential long-term restorative solution in pathologies interrupting efficient myocardial conduction. It is important to understand a material’s bio- and immune-compatibility profiles before it can be safely used as implanted bioelectronic interfaces. Therefore, the next part of this thesis systematically evaluates CNTF’s cellular, hematologic, immunologic, and organ compatibilities. Studies here show that 1) CNTF is biocompatible for both in vitro basic research and in vivo biomedical applications; 2) CNT macrostructures such as CNTF do not belong to the previously established “fiber pathogenicity paradigm” for CNTs. These results also establish baseline biocompatibility requirements for any future CNT-macrostructure-based bioelectronic interfaces. Finally, this thesis presents flexible and transparent neural electrode arrays made from CNT films for integrated optical and electrical investigations. These CNT electrodes are transparent, flexible, and possess low interface impedance. Their capacity to carry out integrated optical and electrical investigations is demonstrated through electrophysiological recording during concurrent calcium imaging in hydra.Item Carbon nanotube woven textile photodetector(American Physical Society, 2018) Zubair, Ahmed; Wang, Xuan; Mirri, Francesca; Tsentalovich, Dmitri E.; Fujimura, Naoki; Suzuki, Daichi; Soundarapandian, Karuppasamy P.; Kawano, Yukio; Pasquali, Matteo; Kono, JunichiroThe increasing interest in mobile and wearable technology demands the enhancement of functionality of clothing through incorporation of sophisticated architectures of multifunctional materials. Flexible electronic and photonic devices based on organic materials have made impressive progress over the past decade, but higher performance, simpler fabrication, and most importantly, compatibility with woven technology are desired. Here we report on the development of a weaved, substrateless, and polarization-sensitive photodetector based on doping-engineered fibers of highly aligned carbon nanotubes. This room-temperature-operating, self-powered detector responds to radiation in an ultrabroad spectral range, from the ultraviolet to the terahertz, through the photothermoelectric effect, with a low noise-equivalent power (a few nW/Hz1/2) throughout the range and with a ZT-factor value that is twice as large as that of previously reported carbon nanotube-based photothermoelectric photodetectors. Particularly, we fabricated a ∼1-m-long device consisting of tens of p+−p− junctions and weaved it into a shirt. This device demonstrated a collective photoresponse of the series-connected junctions under global illumination. The performance of the device did not show any sign of deterioration through 200 bending tests with a bending radius smaller than 100 μm as well as standard washing and ironing cycles. This unconventional photodetector will find applications in wearable technology that require detection of electromagnetic radiation.Item Carbon Nanotubes and Related Nanomaterials: Critical Advances and Challenges for Synthesis toward Mainstream Commercial Applications(American Chemical Society, 2018) Rao, Rahul; Pint, Cary L.; Islam, Ahmad E.; Weatherup, Robert S.; Hofmann, Stephan; Meshot, Eric R.; Wu, Fanqi; Zhou, Chongwu; Dee, Nicholas; Amama, Placidus B.; Carpena-Nuñez, Jennifer; Shi, Wenbo; Plata, Desiree L.; Penev, Evgeni S.; Yakobson, Boris I.; Balbuena, Perla B.; Bichara, Christophe; Futaba, Don N.; Noda, Suguru; Shin, Homin; Kim, Keun Su; Simard, Benoit; Mirri, Francesca; Pasquali, Matteo; Fornasiero, Francesco; Kauppinen, Esko I.; Arnold, Michael; Cola, Baratunde A.; Nikolaev, Pavel; Arepalli, Sivaram; Cheng, Hui-Ming; Zakharov, Dmitri N.; Stach, Eric A.; Zhang, Jin; Wei, Fei; Terrones, Mauricio; Geohegan, David B.; Maruyama, Benji; Maruyama, Shigeo; Li, Yan; Adams, W. Wade; Hart, A. JohnAdvances in the synthesis and scalable manufacturing of single-walled carbon nanotubes (SWCNTs) remain critical to realizing many important commercial applications. Here we review recent breakthroughs in the synthesis of SWCNTs and highlight key ongoing research areas and challenges. A few key applications that capitalize on the properties of SWCNTs are also reviewed with respect to the recent synthesis breakthroughs and ways in which synthesis science can enable advances in these applications. While the primary focus of this review is on the science framework of SWCNT growth, we draw connections to mechanisms underlying the synthesis of other 1D and 2D materials such as boron nitride nanotubes and graphene.