Material Characterization of Nitinol Wires for the Design of Actuation Systems

A series of tests were performed on nickel-titanium alloy wire, also known as nitinol, to determine the plausibility of designing an actuator using this wire as the method of actuation. These tests have been designed to fully characterize how the wire behaves under steady state and transient conditions allowing for a specific wire selection to be made given known actuator specifications which will result in an efficient design. The wire transient data can be used to design a controller which reduces the actuation time. The research done for the overall project covers a wide scope including wire hysteresis, nitinol transition temperature, variable wire resistance, wire actuation as a function of current and pull force, cable fabrication, and wire actuation control to optimize performance. Using these test results, a prototype actuator has been designed using nitinol wire. It has been determined that an actuator can be efficiently designed using this material

B:Ionic Glove: A Soft Smart Wearable Sensory Feedback Device for Upper Limb Robotic Prostheses

Upper limb robotic prosthetic devices currently lack adequate sensory feedback, contributing to a high rejection rate. Incorporating affective sensory feedback into these devices reduces phantom limb pain and increases control and acceptance. To address the lack of sensory feedback we present the B:Ionic glove, wearable over a robotic hand which contains sensing, computation and actuation on board. It uses shape memory alloy (SMA) actuators integrated into an armband to gently squeeze the user's arm when pressure is sensed in novel electro-fluidic fingertip sensors and decoded through soft matter logic. We found that a circular electro-fluidic sensor cavity generated the most sensitive fingertip sensor and considered a computational configuration to convey different information from robot to user. A user study was conducted to characterise the tactile interaction capabilities of the device. No significant difference was found between the skin sensitivity threshold of participants' lower and upper arm. They found it easier to distinguish stimulation locations than strengths. Finally, we demonstrate a proof-of-concept of the complete device, illustrating how it could be used to grip an object, solely from the affective tactile feedback provided by the B:Ionic glove. The B:Ionic glove is a step towards the integration of natural, soft sensory feedback into robotic prosthetic devices.</p

An anthropomorphic design for a minimally invasive surgical system based on a survey of surgical technologies, techniques and training

© 2013 John Wiley & Sons, Ltd. Background: Over the past century, abdominal surgery has seen a rapid transition from open procedures to less invasive methods, such as robot-assisted minimally invasive surgery (MIS). This study aimed to investigate and discuss the needs of MIS in terms of instrumentation and to inform the design of a novel instrument. Methods: A survey was conducted among surgeons regarding their opinions on surgical training, surgical systems, how satisfied they were with them and how easy they were to use. A concept for MIS robotic instrumentation was then developed and a series of focus groups with surgeons were run to discuss it. The initial prototype of the robotic instruments, herein demonstrated, comprises modular rigid links with soft joints actuated by shape memory alloy helix actuators; these instruments are controlled using a sensory hand exoskeleton. Results: The results of the survey, as well as those of the focus groups, are presented here. A first prototype of the system was built and initial laboratory tests have been conducted in order to evaluate this approach. Conclusions: The analysed data from both the survey and the focus groups justify the chosen concept of an anthropomorphic MIS robotic system which imitates the natural motion of the hands

Conceptualization and Fabrication of a Bioinspired Mobile Robot Actuated by Shape Memory Alloy Springs

This work is an experimental study and fabrication of design concepts to validate the feasibility of smart materials and their applications in bio-inspired robotics. Shape-Memory Alloy (SMA) springs are selected as the smart material actuators of interest to achieve locomotion in the proposed mobile robot. Based on a previous design of the robot, this work focuses on both implementing a new locomotion concept and reducing size and weight of the previous design, both using SMA based actuators. Objectives are met in consideration of the conceptual mechanics of circular robot locomotion. The first prototype is a variation of the original design. It consists of a soft, rubber outer shell with three intrinsically attached diametric SMA springs that deform the outer shell during contraction and relaxation. The springs were provided with electrical current in patterns to produce deformation needed to generate momentum and allow the robot to tumble and roll. This design was further improved to provide more stability while rolling. The second design concept is a modification of our previous design leading to reduction in size and weight while maintaining essentially the same mechanism of locomotion. In this case, the SMA springs were externally configured between the end of equi-spaced spokes and the circular core. Upon actuation, the spokes function as diametrically translating legs to generate locomotion. These design concepts are fabricated and experimented on, to determine their feasibility, i.e. whether rolling/tumbling motion is achieved. The scope of the project was limited to demonstration of basic locomotion, which was successful. Future work on this project will address the design of automatic control to generate motion using closed-loop sensor-based actuation

Free radical reactions in atherosclerosis; An EPR spectrometry study

The copper catalysed oxidation of homocysteine has been studied by electron paramagnetic resonance (EPR) spectroscopy and spin trapping techniques to determine the nature of free radical species formed under varying experimental conditions. Three radicals; thiyl, alkyl and hydroxyl were detected with hydroxyl being predominant. A reaction mechanism is proposed involving Fenton chemistry. Inclusion of catalase to test for intermediate generation of hydrogen peroxide showed a marked reduction in amount of hydroxyl radical generated. In contrast, the addition of superoxide dismutase showed no significant effect on the level of hydroxyl radical formed. Enhanced radical formation was observed at higher levels of oxygen, an effect which has consequences for differential oxygen levels in arterial and venous systems. Implications are drawn for a higher incidence of atherosclerotic plaque formation in arteries versus veins. © 2006 - IOS Press and the authors. All rights reserved

Study of the Role of Biologically-Relevant, Labile Nickel Pools in the Maturation of Nickel-Dependent Enzymes

Cellular nickel pools, comprised of static and labile pools of nickel complexes, play important roles in maintaining nickel homeostasis in various organisms (microbes, fungi, and plants), which utilize it as a cofactor of one or more nickel enzymes that catalyze specific reactions and are essential for their proper growth and survival in various ecological niches. Like other metals, tight regulation of cellular nickel levels is critical to prevent toxic effects of nickel deprivation, nickel overload, and ‘free’ nickel. While more static nickel pools include nickel tightly bound to nickel-dependent enzymes, nickel in the labile pool is exchangeable and weakly bound to either nickel chaperones or low-molecular-weight (LMW) ligands, as is the case for many other transition metals. The role of nickel chaperones in enzyme maturation and activation is being extensively investigated, but the importance of cellular LMW complexes in the process remains largely unknown. In this work, I investigated the role of labile nickel pools (both non-proteinaceous and proteinaceous ligands) in the maturation of nickel-dependent enzymes - Nickel Superoxide Dismutase (NiSOD) from Streptomyces coelicolor, and urease and Ni, Fe-hydrogenase from Helicobacter pylori. For the maturation of NiSOD, no chaperone has been characterized for nickel delivery to the active site. Using biochemical assays, mass spectrometry, and spectroscopic methods, I provide compelling evidence that biologically relevant, non-proteinaceous, LMW ligand complexes of nickel with L-histidine are inevitable for the proper maturation of the enzyme. In Helicobacter pylori, which is a human pathogen, there are two nickel dependent enzymes – urease and Ni, Fe hydrogenase both of which require a proteinaceous labile nickel ligand (common nickel-chaperone), HypA for maturation. HypA interacts with HypB for the maturation of Ni, Fe-hydrogenase, and with UreE for the maturation of urease, but what factors determine its differential interaction with its downstream partner proteins are unknown. I interrogated the flexibility and dynamics of HypA by glycine mutations to perturb the maturation of the two nickel enzymes in the pathogen and using in vitro assays I show that the glycine mutations differentially affect the maturation of urease and Ni, Fe – hydrogenase in the pathogen

Metal ion release from metallothioneins: proteolysis as an alternative to oxidation

Metallothioneins (MTs) are among others involved in the cellular regulation of essential ZnII and CuI ions. However, the high binding affinity of these proteins requires additional factors to promote metal ion release under physiological conditions. The mechanisms and efficiencies of these processes leave many open questions. We report here a comprehensive analysis of the ZnII-release properties of various MTs with special focus on members of the four main subfamilies of plant MTs. ZnII competition experiments with the metal ion chelator 4-(2-pyridylazo)resorcinol (PAR) in the presence of the cellular redox pair glutathione (GSH) / glutathione disulfide (GSSG) show that plant MTs from the subfamilies MT1, MT2, and MT3 are remarkably more affected by oxidative stress than those from the Ec subfamily and the well-characterized human MT2 form. In addition, we evaluated proteolytic digestion with trypsin and proteinase K as an alternative mechanism for selective promotion of metal ion release from MTs. Also here the observed percentage of liberated metal ions depends strongly on the MT form evaluated. Closer evaluation of the data additionally allowed deducing the thermodynamic and kinetic properties of the ZnII release processes. The CuI-form of chickpea MT2 was used to exemplify that both oxidation and proteolysis are also effective ways to increase the transfer of copper ions to other molecules. ZnII release experiments with the individual metal-binding domains of Ec-1 from wheat grain reveal distinct differences to the full-length protein. This triggers the question about the roles of the long cysteine-free peptide stretches typical for plant MTs

Mechanistic studies of the metal catalyzed formation of polycarbonates and their thermoplastic elastomers

Studies concerning the formation of industrially useful polycarbonates are the focus of this dissertation. Of particular importance is the biodegradable polymer, poly(trimethylene carbonate) which has a wide range of medical applications. The production of polycarbonates can be achieved by the ring-opening polymerization of cyclic carbonate, or the copolymerization of carbon dioxide and oxiranes or oxetanes. For the production of polycarbonates from these monomers, Schiff base metal complexes have been designed, synthesized, and optimized as catalysts. Detailed kinetic and mechanistic studies have been performed for the ring-opening polymerization of cyclic carbonates, as well as the copolymerization of carbon dioxide and oxiranes or oxetane. In addition, the copolymerization of cyclic carbonates and cyclic esters to modify the mechanical and biodegradable properties of materials used for medical devices has been studied using biocompatible metal complexes. In the process for ring-opening polymerizations of trimethylene carbonate or lactides, Schiff base metal complexes (metal = Ca(II), Mg(II) and Zn(II)) have been shown to be very effective catalysts to produce high molecular weight polymers with narrow polydispersities. Kinetic studies demonstrated the polymerization reactions to proceed via a mechanism first order in [monomer], [catalyst], and [cocatalyst] if an external cocatalyst is applied, and to involve ring-opening by way of acyl-oxygen bond cleavage. The activation parameters (ΔH≠, ΔS≠ and ΔG≠) were determined for ringopening polymerization of trimethylene carbonate, ring-opening polymerization of lactides, and copolymerization of trimethylene carbonate and lactide. In the process for copolymerization of carbon dioxide and oxetane, metal salen derivatives of Cr(III) and Al(III) along with cocatalyst such as n-Bu4NX or PPNX (PPN = bis(triphenylphosphine)iminium, and X = Br, Cl and N3) have been shown to be effective catalysts to provide poly(trimethylene carbonate) with only trace amount of ether linkages. The formation of copolymer is proposed not to proceed via the intermediacy of trimethylene carbonate, which was observed as a minor product of the coupling reaction. To support this conclusion, ring-opening polymerization of trimethylene carbonate has been performed and kinetic parameters have been compared with those from the copolymerization of carbon dioxide and oxetane

Novel Au Carbene Complexes as Promising Multi-Target Agents in Breast Cancer Treatment

Over the past decade, metal complexes based on N-heterocyclic carbenes (NHCs) have attracted great attention due to their wide and exciting applications in material sciences and medicinal chemistry. In particular, the gold-based complexes are the focus of research efforts for the development of new anticancer compounds. Literature data and recent results, obtained by our research group, reported the design, the synthesis and the good anticancer activity of some silver and gold complexes with NHC ligands. In particular, some of these complexes were active towards some breast cancer cell lines. Considering this evidence, here we report some new Au-NHC complexes prepared in order to improve solubility and biological activity. Among them, the compounds 1 and 6 showed an interesting anticancer activity towards the breast cancer MDA-MB- 231 and MCF-7 cell lines, respectively. In addition, in vitro and in silico studies demonstrated that they were able to inhibit the activity of the human topoisomerases I and II and the actin polymerization reaction. Moreover, a downregulation of vimentin expression and a reduced translocation of NF-kB into the nucleus was observed. The interference with these vital cell structures induced breast cancer cells’ death by triggering the extrinsic apoptotic pathway