176 research outputs found

    Paper as smart support for bioreceptor immobilization in electrochemical paper-based devices

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    The use of paper as a smart support in the field of electrochemical sensors has been largely improved over the last 15 years, driven by its outstanding features such as foldability and porosity, which enable the design of reagent and equipment-free multi-analysis devices. Furthermore, the easy surface engineering of paper has been used to immobilize different bioreceptors, through physical adsorption, covalent bonding, and electrochemical poly-merization, boosting the fine customization of the analytical performances of paper-based biosensors. In this review, we focused on the strategies to engineer the surface of the paper for the immobilization of (bio)recog-nition elements (eg., enzymes, antibodies, DNA, molecularly imprinted polymers) with the overriding goal to develop accurate and reliable paper-based electrochemical biosensors. Furthermore, we highlighted how to take advantage of paper for designing smart configurations by integrating different analytical processes in an eco-designed analytical tool, starting from the immobilization of the (bio)receptor and the reagents, through a designed sample flow along the device, until the analyte detection

    Bioinspired Soft Robotics: state of the art, challenges, and future directions

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    Purpose of Review: This review provides an overview of the state of the art in bioinspired soft robotics with by examining advancements in actuation, functionality, modeling, and control. Recent Findings: Recent research into actuation methods, such as artificial muscles, have expanded the functionality and potential use of bioinspired soft robots. Additionally, the application of finite dimensional models has improved computational efficiency for modeling soft continuum systems, and garnered interest as a basis for controller formulation. Summary: Bioinspiration in the field of soft robotics has led to diverse approaches to problems in a range of task spaces. In particular, new capabilities in system simplification, miniaturization, and untethering have each contributed to the field's growth. There is still significant room for improvement in the streamlining of design and manufacturing for these systems, as well as in their control

    Integrated design approach for responsive solar-shadings in double skin facades in hot arid climate

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    Ph. D. Thesis.To deliver climate adaptive architecture, current trends in architecture are directed towards dynamic and responsive building skins. ‘Responsive building skin’ is used to describe the ability of building envelopes to adapt in real time in response to external environmental conditions. Recent attention has focused on ‘soft robotics’ approach which uses soft and/or extensible materials to deform with muscle‐like actuation, mimicking biological systems. Material embedded actuation can autonomously alter shading systems’ morphology stimulated by external environmental conditions. Passively thermally‐activated shading systems offer responsive actuation by solar‐radiation and stratified hot air in a double skin façade (DSF) without recourse to energy consuming systems. This research identifies the intersection between bio‐inspiration, folding principles and smart materials to integrate the underlying mechanisms in responsive solar‐shading systems and assesses their environmental performance. The thesis proposes an interdisciplinary mixed methodology linking hands‐on experimentation with environmental performance simulation of responsive building skins. ‘Practice‐led approach’ is used to explore the design potential of responsive systems using smart materials. ‘Computational Fluid Dynamics’ (CFD) numerical methods are used to measure the impact of responsive solar‐shading systems on multiple environmental factors in a DSF cavity. This helps the design decisions, selection and customisation of smart materials. Hands‐on experimentation is used to explore various prototypes, leading to the selection of a folded prototype, to be simulated for environmental performance. Solar‐shading systems are tested within a DSF, in an hot arid climate. Flat and folded solar‐shading devices are installed in a DSF cavity with three aperture sizes (30%, 50% & 70%) to represent the responsive system states. Point‐in‐time simulations are carried at 9:00 am, 12:00 pm and 15:00 pm in peak summer and winter day. The developed analytical design framework presents different design parameters for responsive solar‐shading systems to guide decision‐making in research of climate actuated smart shading systems. Keywords: Responsive skins, Adaptive facades, Soft robotics, Bio‐inspiration, Origami, Deployable structures, Actuation, Smart materials, Shape memory alloys, Double skin facades, Energy efficiency, Digital simulation, CFD Modelling

    Surface tension-powered self-assembly of micro structures - The state-of-the-art

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    Cellulose-Based Biosensing Platforms

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    Cellulose empowers measurement science and technology with a simple, low-cost, and highly transformative analytical platform. This book helps the reader to understand and build an overview of the state of the art in cellulose-based (bio)sensing, particularly in terms of the design, fabrication, and advantageous analytical performance. In addition, wearable, clinical, and environmental applications of cellulose-based (bio)sensors are reported, where novel (nano)materials, architectures, signal enhancement strategies, as well as real-time connectivity and portability play a critical role

    Block copolymer micellization, and DNA polymerase-assisted structural transformation of DNA origami nanostructures

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    DNA Nanotechnology allows the synthesis of nanometer sized objects that can be site specifically functionalized with a large variety of materials. However, many DNA structures need a higher ionic strength than that in common cell culture buffers or in bodily fluids to maintain their integrity and can be degraded quickly by nucleases. The aim of this dissertation was to overcome this deficiency with the help of cationic PEG-poly-lysine block copolymers that can electrostatically cover the DNA nanostructures to form “DNA origami polyplex micelles” (DOPMs). This straightforward, cost-effective and robust route to protect DNA-based structures could therefore enable applications in biology and nanomedicine, where un-protected DNA origami would be degraded. Moreover, owing to high polarity, the DNA-based structures are restricted to the aque-ous solution based buffers only. Any attempt to change the favorable conditions, leads to the distortion of the structures. In this work it was demonstrated that, by using the polyplex micellization strategy, the organic solubility of DNA origami structures can be improved. The strategy was also extended to functional ligands that are otherwise not soluble in organic solvents. With this strategy, it is now also possible to perform organic solution reactions on the DNA-based structures, opening up the possibility to use hydro-phobic organic reagents to synthesize novel materials. The polyplex micellization strategy therefore presents a cheap, robust, modular, reversible and versatile method to not only solubilize DNA structures in organic solvents but also improve their stability in biological environments. A third project was based on the possibility to synthesize complementary sequences to single-stranded gap regions in the DNA origami scaffold cost-effectively by a DNA polymerase rather than by a DNA synthesizer. For this purpose, four different wireframe DNA origami structures were designed to have single-stranded gap regions. The introduction of flexible gap regions resulted in fully collapsed or partially bent structures due to entropic spring effects. These structures were also used to demonstrate structural transformations with the help of DNA polymerases, expanding the collapsed bent structures to straightened tubes. This approach presents a powerful tool to build DNA wireframe structures more material-efficiently, and to quickly prototype and test new wireframe designs that can be expanded, rigidified or mechanically switched.:Abstract v Publications vii Acknowledgements ix Contents xiii Chapter 1 Introduction 1 1.1 Nanotechnology 1 1.1.1 History of nanotechnology 1 1.1.2 Phenomena that occur at nanoscale 4 1.1.3 Nature’s perspective of nanotechnology 4 1.1.4 Manufacturing nanomaterials 6 1.2 Deoxyribonucleic acid (DNA) 8 1.2.1 DNA, the genetic material, “The secret of life” 8 1.2.2 Structure of DNA 9 1.2.3 DNA synthesis 15 1.2.4 Stability of DNA 18 1.3 DNA nanotechnology 20 1.3.1 Historical development 20 1.3.2 DNA tile motifs 21 1.3.3 Directed nucleation assembly and algorithmic assembly 23 1.3.4 Scaffolded DNA origami and single-stranded DNA tiles 25 1.3.5 Expanding the design space offered by DNA 27 1.3.6 Assembling heterogeneous materials with DNA 30 1.3.7 Functional devices built using DNA nanostructures 35 Chapter 2 Motivation and objectives 40 Chapter 3 Block copolymer micellization as a protection strategy for DNA origami 42 3.1 Introduction 42 3.1.1 Cellular delivery of DNA nanostructures 42 3.1.2 The need for stability of DNA nanostructures 43 3.1.3 Non-viral gene therapy 44 3.2 Results and discussions 46 3.2.1 Strategy to form DNA origami polyplex micelles (DOPMs) 46 3.2.2 Optimizations 46 3.2.3 Decomplexation 53 3.2.4 Stability tests 55 3.2.5 Short PEG-PLys block copolymer 58 3.2.6 Compatibility with bulky ligands 59 3.2.7 Accessibility of handles on DOPMs 63 3.3 Conclusion 64 3.4 Outlook and state of the art 65 3.5 Methods 67 3.5.1 DNA origami folding 67 3.5.2 Preparation of ssDNA functionalized AuNPs 68 3.5.3 Agarose gel electrophoresis 69 3.5.4 Block copolymer preparation 70 3.5.5 DNA origami polyplex micelle preparation 70 3.5.6 Decomplexation of DOPM using dextran sulfate 73 3.5.7 Stability tests 74 3.5.8 tSEM characterization 75 3.5.9 AFM imaging 76 Chapter 4 Improving organic solubility and stability of DNA origami using polyplex micellization 77 4.1 Introduction 77 4.2 Results and discussions 79 4.2.1 Strategy for organic solubility of DNA origami 79 4.2.2 Proof of concept using AuNPs functionalized with ssDNA 80 4.2.3 Extending the strategy to DNA origami 82 4.2.4 Optimizations 86 4.2.5 Compatibility with functional ligands 88 4.2.6 Functionalization of DNA origami in organic solvent 94 4.3 Conclusion and outlook 95 4.4 Methods 97 4.4.1 Conjugation of functional ligands to DNA origami 97 4.4.2 Organic solubility 98 4.4.3 Reactions in organic solution on DOPMs 99 4.4.4 Fluorescence imaging using gel scanner 100 Chapter 5 Structural transformation of wireframe DNA origami via DNA polymerase assisted gap-filling 101 5.1 Introduction 101 5.2 Results and discussion 102 5.2.1 Design of the structures 102 5.2.2 Folding of gap-structures 105 5.2.3 Single-stranded DNA binding proteins 107 5.2.4 Gap filling with different polymerases 109 5.2.5 Gap filling with Phusion high-fidelity DNA polymerase 111 5.2.6 Optimization of the extension reaction using T4 DNA polymerase 115 5.2.7 Secondary structures 121 5.2.8 Folding kinetics of gap origami 124 5.2.9 Bending of tubes 125 5.3 Conclusion 126 5.4 Outlook 127 5.5 Methods 128 5.5.1 DNA origami folding 128 5.5.2 Gap filling of the wireframe DNA origami structures 128 5.5.3 Agarose gel electrophoresis 130 5.5.4 PAGE gel analysis 130 5.5.5 tSEM characterization 131 5.5.6 AFM imaging 131 5.5.7 AGE based folding-yield estimation 132 5.5.8 Gibbs free energy simulation using mfold 132 5.5.9 Staple list for folding the DNA origami triangulated structures 132 Appendix 134 A.1 Additional figures from chapter 3 134 A.2 Additional figures from chapter 4 137 A.3 Additional figures from chapter 5 149 Bibliography 155 ErklĂ€rung 17

    Origami-inspired nanofabrication utilizing physical and magnetic properties of in situ grown carbon nanotubes

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 123-133).Carbon nanotubes (CNTs), in particular the vertically-aligned variety grown through a plasma enhanced chemical vapor deposition (PECVD)-based process, are highly versatile nanostructures that can be used in a variety of nanomanufacturing applications. However, process and material compatibility issues have prevented the nanotubes from becoming more fully integrated into various micro- and nanomanufacturing applications. In this thesis, the integration of in situ CNT growth with a 3-D nanomanufacturing platform, namely the Nanostructured Origami TM process, will be shown. Due to the high temperatures involved in CNT growth, a new origami membrane material, titanium nitride (TiN), is introduced. This new origami membrane serves as an excellent diffusion barrier layer throughout the CNT growth process while promoting consistent nanotube growth and maintaining electrical conductivity to the CNTs. Various further modifications are made to the origami process, for example in metallization techniques, to accommodate the addition of CNTs to origami devices. Based on the presented CNT-origami process, a functioning microscale supercapacitor is also fabricated and tested. The integration of high surface area CNT electrodes with a unique 3-D device geometry results in a fabfriendly, high-performance supercapacitor that can easily be integrated as an onboard power source in self-powered microsystem applications. Finally, the magnetic properties of our in situ grown CNTs, derived from their naturally occurring, tip-encapsulated catalyst particles, will be characterized. Furthermore, these properties will be used to magnetically actuate, align, and latch individual as well as large arrays of CNTs and the entire membranes on which they are grown. The magnetic behaviors of CNTs and their underlying membranes will be investigated through computer simulation and experimental verification.by Hyun Jin In.Ph.D

    Liquid Crystal Anchoring Control and its Applications in Responsive Materials

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    Liquid crystals (LCs), owing to their anisotropy in molecular ordering, are of interests not only in the display industry, but also in the soft matter community, e.g., to direct colloidal assembly and phase separation of surfactants, and to actuate two-dimensional (2D) sheets into three-dimension (3D). The functionality and performance of LC materials extensively rely on the molecular ordering and alignment of LCs, which are dictated by LC anchoring at various boundaries. Therefore, this thesis focuses on the study of LC anchoring from both small molecule LCs and liquid crystal monomers (LCMs), which in turn guides my design of surface topography and surface chemistry to control formation of uniform LC defect structures over cm2 samples under complex boundary conditions. The ability to precisely embed defect structures in a LC material also allows me to exploit the responsiveness of LCs to create actuators and scaffolds to (dis)assemble nano- and micro-objects. Specifically, by exploiting the bulk disclinations formed in the nematic phase of 4-octyl-4’-cyanobiphenyl (8CB) surrounding the micropillar arrays, we demonstrate (dis)assembly of gold nano-rods (AuNRs) for dynamic tuning of surface plasmon resonance (SPR). Due to the highly temperature-sensitive elastic anisotropy of 8CB, the bulk disclinations and consequently the AuNR assemblies and SPR properties can be altered reversibly by heating and cooling the LC system. Then we design and synthesize a new type of nematic LCMs with a very large nematic window. Therefore, they can be faithfully aligned at various boundary conditions, analogous to that of small molecule LCs. After crosslinking LCMs into liquid crystal polymers (LCPs), we are able to study the LC assembly, director field, and topological defects using scanning electronic microscopy (SEM) at the 100 nm resolution. We then turn our attention to direct LCM alignment through controlling of surface chemistry and topography. We demonstrate the essential role of surface chemistry in the fabrication of liquid crystal elastomer (LCE) micropillar arrays during soft lithography. A monodomain LCM alignment is achieved in a poly(2-hydroxyethyl methacrylate) coated polydimethylsiloxane (PDMS) mold. After crosslinking, the resultant LCE micropillars display a large radial strain (~30%) when heated across the nematic-isotropic phase transition temperature (TNI). The understanding of surface alignment in LCMs is then transferred to LCEs with embedded topological defects. On micron-sized one-dimensional channels with planar surface chemistry, LCMs can be faithfully oriented along the local channel direction. After crosslinking, the 2D LCE sheets show pre-programmed shape transformation to complex 3D structures through bending and stretching of local directors when heated above TNI. Last, we control LC alignment and defect formation on a flat surface simply by using chemical patterns. Planar anchored SU8 is photopatterned on homoetropically anchored dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP) coated glass. By exploiting the pattern geometry, thus, boundary conditions, in combination with anisotropy of LC elasticity, we show that LC orientation can be precisely controlled over a large area and various types of topological defects are generated. Such defect structures can be further used to trap micro- and nanoparticles
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