A Review of Smart Materials in Tactile Actuators for Information Delivery

As the largest organ in the human body, the skin provides the important sensory channel for humans to receive external stimulations based on touch. By the information perceived through touch, people can feel and guess the properties of objects, like weight, temperature, textures, and motion, etc. In fact, those properties are nerve stimuli to our brain received by different kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can stimulate these receptors and cause different information to be conveyed through the nerves. Technologies for actuators to provide mechanical, electrical or thermal stimuli have been developed. These include static or vibrational actuation, electrostatic stimulation, focused ultrasound, and more. Smart materials, such as piezoelectric materials, carbon nanotubes, and shape memory alloys, play important roles in providing actuation for tactile sensation. This paper aims to review the background biological knowledge of human tactile sensing, to give an understanding of how we sense and interact with the world through the sense of touch, as well as the conventional and state-of-the-art technologies of tactile actuators for tactile feedback delivery

Advances in scalable gas-phase manufacturing and processing of nanostructured solids: A review

Although the gas-phase production of nanostructured solids has already been carried out in industry for decades, only in recent years has research interest in this topic begun to increase. Nevertheless, despite the remarkable scientific progress made recently, many long-established processes are still used in industry. Scientific advancements can potentially lead to the improvement of existing industrial processes, but also to the development of completely new routes. This paper aims to review state-of-the-art synthesis and processing technologies, as well as the recent developments in academic research. Flame reactors that produce inorganic nanoparticles on industrial- and lab-scales are described, alongside a detailed overview of the different systems used for the production of carbon nanotubes and graphene. We discuss the problems of agglomeration and mixing of nanoparticles, which are strongly related to synthesis and processing. Finally, we focus on two promising processing techniques, namely nanoparticle fluidization and atomic layer deposition

Channeling of protons through carbon nanotubes

This book contains a thorough theoretical consideration of the process of proton channeling through carbon nanotubes. We begin with a very brief summary of the theoretical and experimental results of studying ion channeling through nanotubes. Then, the process of ion channeling is described briefly. After that, the crystal rainbow effect is introduced. We describe how it was discovered, and present the theory of crystal rainbows, as the proper theory of ion channeling in crystals and nanotubes. We continue with a description of the effect of zero-degree focusing of protons channeled through nanotubes. It is shown that the evolution of the angular distribution of channeled protons with the nanotube length can be divided in the cycles defined by the rainbow effect. Further, we analyze the angular distributions and rainbows in proton channeling through nanotubes. This is done using the theory of crystal rainbows. The angular distributions are generated by the computer simulation method, and the corresponding rainbow patterns are obtained in a precise analysis of the mapping of the impact parameter plane to the transmission angle plane. We demonstrate that the rainbows enable the full explanation of the angular distributions. We also investigate how the effect of dynamic polarization of the carbon atoms valence electrons influences the angular and spatial distributions of protons transmitted through short nanotubes in vacuum and embedded in dielectric media. In addition, we explore the channeling star effect in 1 GeV proton channeling through bundles of nanotubes, which appears when the proton beam divergence angle is larger than the critical angle for channeling.Comment: 58 pages, 22 figures, the book "Channeling of Protons through Carbon Nanotubes" (published by Nova Science Publishers 2011

Preparation and Characterization of Desmopressin Peptide Attached Multi-Walled Carbon Nanotube

Desmopressin, a synthetic analogue of vasopressin, has many applications in medicine including diabetes insipidus, night bedwetting, and hemophillia A. In this work, the attachment of desmopressin to multi-walled carbon nanotubes (MWCNTs), functionalized by HNO3 and H2SO4 treatment was first used to remove the unwanted catalyst from MWCNTs and meanwhile introduced carboxylic acid groups onto the surface of MWCNTs. These carboxylic groups were then used as reaction sites for the attachment of desmopressin peptide to MWCNTs. The reagents used for the attachment were oxalyl chloride and dicyclohexylcarbodiimide (DCC). The Covalent attachment of desmopressin to functionalized MWCNTs was confirmed by Fourier Transform infrared spectroscopy (FT-IR), Raman scattering, and Field Emission Scanning Electron Microscopy (FESEM).HIGHLIGHTS•The conversion of carboxylic groups to oxalyl chloride on the surface of MWCNTs.•The conversion of carboxylic groups to O-acylisourea on the surface of MWCNTs.•DCC and oxalyl chloride activate groups on MWCNTs for nucleophilic substitution.•Desmopressin is a cyclic nonapeptide with one disulfide bridge.•The Covalent attachment of desmopressin to functionalized MWCNTs

A PRECISION INSTRUMENT FOR RESEARCH INTO NANOLITHOGRAPHIC TECHNIQUES USING FIELD-EMITTED ELECTRON BEAMS

Nanomanufacturing is an active research area in academia and industry due to the ever-growing demands for precision surface modifications of thin films or substrates with nanoscale features. Conventional lithographic techniques face many challenges as they approach their fundamental limits. Consequently, new nanomanufacturing tools, fabrication techniques, and precision instruments are being explored and developed to meet these challenges. It has been hypothesized that direct-write nanolithography might be achieved by using a field-emitted electron beam for nanomachining. This dissertation moves this research one step closer by developing a precision instrument that can enable the integration of direct-write nanolithography by a field-emitted electron beam with dimensional metrology by scanning tunneling microscopy. First, field emission from two prospective electron sources, a carbon nanotube field emitter and a sharp tungsten field emitter, is characterized at distances ranging from sub-micrometer to a few micrometers. Also, the design and construction of a low thermal drift piezoelectric linear motor is described for tip-sample approach. Experiments indicate that: the step size is highly repeatable with a standard deviation of less than 1.2 nm and the thermal stability is better than 40 nm/◦C. Finally, the design and construction of the instrument are presented. Experiments indicate that: the instrument is operating properly in scanning tunneling microscope mode with a resolution of less than 2 Å

Synthesis, characterization and evaluation of ionic liquids and polymeric ionic liquids/functionalized multiwalled carbon nanotubes for Cr(VI) adsorption.

Doctoral Degree. University of KwaZulu-Natal, Pietermaritzburg.In this study, a series of imidazolium and pyridinium-based ionic liquids (ILs), polymeric ionic liquids (PILs), and their carbon nanotubes-functionalized composites were synthesized, characterized and applied as potential adsorbents for hexavalent Cr(VI). Polymeric ionic liquids of different polymerizable moieties (vinyl and styrenic moieties) were studied. Furthermore, multi-walled carbon nanotubes (MWCNTs) were synthesized, characterized and dispersed on both imidazolium and pyridinium-based ILs and PILs, respectively. Thermal studies revealed that vinyl pyridinium PILs possess good thermal stability than the vinyl imidazolium counterparts. The size of the counter-anions bromide (Br-), hexafluorophosphate (PF6-), and bis(trifluoromethanesulfonyl) imide (TFSI-) and the charge delocalization in cationic rings greatly influenced the glass transition temperatures of PILs. Expectedly, pyridinium and imidazolium-based PILs with hexafluorophosphate ions showed poor solubility in polar protic solvents (water, methanol) and good solubility in polar aprotic solvents (DMSO, DMF, THF) except acetone (a dipolar aprotic solvent). The as-synthesized ILs/MWCNT composites were characterized using FTIR spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermal analysis. The results obtained indicate that the pyridinium-based ILs exhibited higher decomposition temperatures (above 400 °C) compared to imidazolium-based ILs counterparts (onset decomposition at 250 °C) with poor water-solubility and their glass transition temperatures were dependent on ion mobility. The effect of the alkyl lateral chain (propyl and isopropyl) at the first and third position of imidazolium and N-position of pyridinium cationic rings towards their thermal stability, conductivity, and solubility of the ionic liquids was investigated. Their solubilities in different polar and non-polar solvents were also investigated. Spectroscopic and microscopic analyses confirmed the formation of the ILs/MWCNT composites with new functionalities and unaltered surface morphology of carbon nanotubes. Pyridinium and imidazolium-based PILs/MWCNT composites were characterized by thermal, spectroscopic, and electron microscopy techniques. It was observed that the composites were thermally stable compared to the corresponding precursors and were insoluble in polar aprotic solvents. For application, solid-liquid adsorption process was used in the adsorption of Cr(VI) from aqueous solution using the as-synthesized ILs/MWCNT and PILs/MWCNT composites as adsorbents. Under batch adsorption experiments, the effect of solution pH, contact time and initial concentration of Cr(VI) were investigated. It was established that the adsorption of Cr(VI) took place under acidic conditions (pH=2-3), thereby confirming significant adsorption of dichromate (Cr2O7-) and hydrochromate (HCrO4-) anions. At lower pH values, the ionic and π-anionic electrostatic interactions between the positively-charged regions of the composites and Cr(VI) were believed to have facilitated the adsorption of anionic (Cr2O7-) and (HCrO4-). Adsorption results obtained based on contact time showed that increase in contact time gradually increases the adsorption of Cr(VI) within 2 h. However, further increase in experimental contact time above 2 h insignificantly affected the adsorption of Cr(VI) due to early or quick oversaturation of the surface active sites on the adsorbents. The adsorption of Cr(VI) onto ILs/MWCNT and PILs/MWCNT composites fitted well into both Langmuir and Freundlich adsorption isotherms. However, the homogeneity/heterogeneity nature of the adsorbents relied on the diversified nature of the composites, which includes bulky pyridinium and imidazolium organic cations with delocalized charges, some large counter anions and the graphitic functional carbon groups. In order to understand the mechanisms of the adsorption of Cr(VI) onto ILs/MWCNT and PILs/MWCNT composites, pseudo-second-order kinetic model was employed. The results obtained showed that the calculated maximum adsorption capacities (qecal) and experimental maximum adsorption capacities (qe.exp) depict high correlation co-efficiencies (R2>0.99) confirming the applicability and feasibility of pseudo-second-order model on the adsorption of Cr(VI) in this study.Abstract available in pdf