Academic literature on the topic 'Polymer sensor; Self-assembly'

The use of ultrathin polymer films as sensoactive layers in chemical sensors has received great interest in recent years due to many advantages such as the wide choice of polymeric system (polymer types and/or combination, dopants in conducting polymers, etc), and the possibility of tailoring the properties of these films in terms of sensitivity and selectivity by an efficient control of the film formation process [1]. Among the techniques used for ultrathin films formation, self-assembly (SA) offers several advantages since the substrate can take any form and size, deposition time is independent of the substrate area, there are no requirements for additional equipments and/or clean rooms, and a large quantity of materials can be assembled into thin films [2-8].

Boronic acid-containing polycyclosiloxane showed unique self-assembly nanofilm formation (6 nm film thickness) on various substrates and provided film-based metal ion sensor capability through dynamic covalent bonding.

ABSTRACTPoint-of-care systems require highly sensitive, quantitative and selective detection platforms for the real-time multiplexed monitoring of target analytes. To ensure facile development of a sensor, it is preferable for the detection assay to have minimal chemical complexity, contain no wash steps and provide a wide and easily adaptable detection range for multiple targets. Current studies involve label-free detection strategy for relevant clinical molecules such as heme using G-quadruplex based self-assembly. We have explored the measurement of binding and kinetic parameters of various G-quadruplex/heme complexes which are able to self-associate to form a DNAzyme with peroxidase mimicking capabilities and are critical to nucleic acid research. The detection strategy includes immobilizing the G-quadruplex sequences within a polymer matrix to provide a self-assembly based detection approach for heme that could be translated towards other clinically relevant targets.

Persulfurated asterisks functionalized with six carboxylic groups form a strongly green phosphorescent coordination polymer upon addition of Pb²⁺ ions in aqueous solution. The self-assembly process is selective and reversible, enabling Pb²⁺ sensing with a detection limit of 6.0 × 10⁻⁷ M.

In recent years, a great deal of attention has been paid on coating the surface of glass and related inorganic substrate with a layer of polymers having special properties to prepare various functional materials. On a smooth surface of glass, the adhesion of a conductive polymer is generally poor. The increase of the surface adhesion was achieved through a chemical pre-treatment. One of the method is to generate a self-assembly monolayer or patterned SAM monolayer to increase the surface adhesion property of glass surface towards polymer solutions [1,2]. Self-assembled monolayers (SAMs) are monomolecular layers which are spontaneously formed upon immersing a solid substrate into a solution containing functional molecules. SAMs can be prepared using different types of molecules and different substrates. Aminosilanes such as (3-Aminopropyl)-triethoxysilane (APTES) are attractive for such applications [3]. Particularly, aminosilanes have the advantage of catalytic activity by the amine group that facilitates formation of siloxane bonds with surface silanols. In present study, a 3-step procedure for the introduction of APTES on glass pieces is described. After chemisorptions of APTES, poly (aniline-co-m-aminobenzoic acid) synthesised by inverse emulsion polymersation route was coated on to the functionalised glass surface in the form of a solution prepared in DMSO. The modified glass was characterized mainly by IR spectroscopy and contact angle measurement. The coated glass was used for ester sensing.

A graphene/polyaniline (rGO/PANi) nanocomposite was synthesized by solution blending method and deposited on to a nylon-6 membrane via vacuum assisted self-assembly (VASA) method to fabricate a flexible material applied as a chemoresistive gas sensor for trimethylamine (TMA). The morphological and structural characterization of surfaced adsorbed polymer nanocomposite was carried out by FT-IR, SEM, UV-Vis and surface profilometry. While, electrical property was carried out by four-point probe measurement. Prepared rGO/PANi nanocomposite has a percolation threshold around 0.40% vol. fraction, with a conductivity of 8.28 S/m (rsd = 3.0%, n=3) and thickness around 38.58 μm (rsd = 7.63%, n=3. The composite sensor exhibited linear range from 45 to 230 mg/L (r2= 0.9962) and the calculated limit of detection was 25.30 mg/L. It exhibited a repeatable response to TMA gas.

Touch (or tactile) sensors are gaining renewed interest as the level of sophistication in the application of minimally invasive surgery and humanoid robots increases. The spatial resolution of current large-area tactile sensors (greater than 1 cm2) lag human fingers by over an order of magnitude. Using metal and semiconducting nanoparticles, a ~100 nm thick, large area thin-film device working on the principles of electron tunneling is self-assembled, such that the change in current density through the film and the electroluminescence light intensity are linearly proportional to the local stress. By pressing a United States 1 cent coin (and also a copper grid) on the device a well resolved stress image by focusing the electroluminescence light directly on CCD is obtained. Both the lateral and height resolution of texture are comparable to human finger at similar stress levels of ~10 KPa. The fabrication of the film is based on self-assembly of polyelectrolytes, and metal and semiconducting nanoparticles in a layered architecture. The polyelectrolyte layer functions as the dielectric tunneling barrier and the nanoparticles function as the base for tunneling electrons. The assembly of the device can be simplified by incorporating the functionality of the polyelectrolyte and the nanoparticles in a single composite medium. A non-micellar mineralization process for the synthesis of multifunctional nanocomposite materials is also reported as a possible building block for the assembly of tactile sensor. The non-micellar method results in the synthesis of monodisperse semi-conducting nanoparticles templated on polymer chains dissolved in solution at high yield. The monodispersity is achieved due to the beaded necklace morphology of the polyelectrolyte chains in solution where the beads are nanometer-scale nodules in the polymer chain and the nanoparticles are confined to the beads. The resultant structure is a nanoparticle studded necklace where the particles are imbedded in the beads. Multiple cycles of the synthesis on the polymer template yield nanoparticles of identical size, resulting in a nanocomposite with high particle fraction. The resultant nanocomposite has beaded-fibrilar morphology with imbedded nanoparticles, and can be solution cast to make electroluminescent thin film devices. The concept is further modified for synthesis of metal nanoparticles on polyelectrolyte templates with isolated beaded morphology.<br>Ph. D.

La present tesis contribueix a donar una nova visió dins de l'àrea de modificació de superfícies, la qual implica la nanoestructuració de substrats fent servir la tècnica d'auto-assemblatge per a dipositar sobre aquests un polímer conductor mitjançant deposició química en fase vapor per plasma. L'ús de polímers conductors ha despertat un creixent interès en el desenvolupament de sensors químics per a l'anàlisi de gasos en aplicacions d'enginyeria electrònica. La contínua reducció de mida en aquests dispositius ha encoratjat la proposta d'un mètode alternatiu per aconseguir estructures de rang nanomètric, així com per solucionar problemes com la falta d'adherència entre substrat i polímer, disminuir els límits de detecció o escurçar els temps de resposta.<br/><br/>En aquesta investigació s'ha treballat amb monocapes amb un grup pirrol terminal per tal de potenciar la nucleació i creixement de pel·lícules de polipirrol polimeritzades mitjançant plasma. A més, les monocapes han aportat millores en l'adhesió interfacial de l'estructura polímer/metall. Així mateix, s'han dopat les pel·lícules primes de polipirrol per tal d'obtenir la seva forma conductora, les propietats elèctriques de les quals permeten utilitzar-ho com a sensor químic. La seva exposició a un vapor comporta canvis en la conductivitat del polímer, a través dels quals es pot identificar i quantificar l'esmentat analit.<br/><br/>L'auto-assemblatge i la deposició del polímer són els factors claus en aquesta investigació. Per tant, s'han utilitzat diverses tècniques de caracterització de superfícies com XPS, TOF-SIMS, FT-IR o SEM, per estudiar les seves propietats físiques i químiques. Igualment, l'ús de l'AFM ha estat de gran ajut per investigar el procés de nucleació i la topografia de les pel·lícules. A més, la tècnica de les quatre puntes ha proporcionat una excel·lent eina per realitzar mesures de conductivitat a les pel·lícules primes. Finalment, les pel·lícules polimeritzades per plasma han mostrat una gran sensibilitat al diòxid de carboni, demostrant la seva capacitat per ser utilitzades com a sensors químics.<br>La presente tesis contribuye a dar una nueva visión dentro del área de modificación de superficies, la cual implica la nanoestructuración de sustratos utilizando la técnica de auto-ensamblado para depositar sobre éstos un polímero conductor mediante deposición química en fase vapor por plasma. El uso de polímeros conductores ha despertado un creciente interés en el desarrollo de sensores químicos para el análisis de gases en aplicaciones de ingeniería electrónica. La continua reducción de tamaño en estos dispositivos ha alentado la propuesta de un método alternativo para conseguir estructuras de rango nanométrico, así como para solucionar problemas tales como la falta de adherencia entre sustrato y polímero, disminuir los límites de detección o acortar los tiempos de respuesta.<br/><br/>En esta investigación se ha trabajado con monocapas con un grupo pirrol terminal para potenciar la nucleación y crecimiento de películas de polipirrol polimerizadas mediante plasma. Además, las monocapas han aportado mejoras en la adhesión interfacial de la estructura polímero/metal. Asimismo, se han dopado las películas delgadas de polipirrol para obtener su forma conductora, cuyas propiedades eléctricas permiten utilizarlo como sensor químico. Su exposición a un vapor conlleva cambios en la conductividad del polímero, a través de los cuales se puede identificar y cuantificar dicho analito.<br/><br/>El auto-ensamblaje y la deposición del polímero son los factores claves en esta investigación. Por lo tanto, se han utilizado diversas técnicas de caracterización de superficies, como XPS, TOF-SIMS, FT-IR o SEM, para estudiar sus propiedades físicas y químicas. Igualmente, el uso del AFM ha sido de gran valor para investigar el proceso de nucleación y la topografía de las películas. Además, la técnica de las cuatro puntas ha proporcionado una excelente herramienta para realizar medidas de conductividad en películas delgadas. Finalmente, las películas polimerizadas por plasma han mostrado una gran sensibilidad al dióxido de carbono, con lo cual han demostrado su capacidad para ser utilizados como sensores químicos.<br>This thesis contributes a new insight into surface modification involving substrates nanostructuration by self-assembly to deposit on them a conducting polymer through plasma enhanced chemical vapor deposition. The use of conducting polymers has gained growing interest in the development of chemical sensor arrays for gas analysis in electronic engineering applications. The size reduction in these devices has encouraged the proposal of an alternative method to achieve structures at nanometer range, as well as overcoming problems like lack of adhesion between substrate and polymer, lower limits of detection or shorten response times.<br/><br/>The investigation has dealt with the use of pyrrole terminated monolayers to enhance the nucleation and growth of polypyrrole plasma polymerized films. In addition, monolayers provide an improvement in the interfacial adhesion of the polymer/metal structure. Furthermore, polymeric thin films have been doped to obtain the conducting form of polypyrrole, of which electric properties enable to use it as a chemical sensor. Exposure to vapors leads to changes in polymer conductivity, by which analytes can be identified and quantified.<br/><br/>Self-assembly and polymer deposition are key factors in this research, as a consequence surface characterization techniques, such as XPS, TOF-SIMS, FT-IR or SEM, have been employed to study their physical and chemical characteristics. Especially interesting have been the use of AFM to investigate the nucleation process and the film topography. Moreover, the four-point probe technique has provided an excellent tool to perform conductivity measurements on thin films. Besides, plasma polymerized films have shown a high sensitivity to carbon dioxide in order to demonstrate their aptitudes to be utilized as a chemical sensor.

This thesis addresses the development of materials, technologies and circuits applied for the fabrication of a new class of microelectronic devices that are relying on a three-dimensional shape variation namely shapeable microelectronics. Shapeable microelectronics has a far-reachable future in foreseeable applications that are dealing with arbitrarily shaped geometries, revolutionizing the field of neuronal implants and interfaces, mechanical prosthetics and regenerative medicine in general. Shapeable microelectronics can deterministically interface and stimulate delicate biological tissue mechanically or electrically. Applied in flexible and printable devices shapeable microelectronics can provide novel functionalities with unmatched mechanical and electrical performance. For the purpose of shapeable microelectronics, novel materials based on metallic multilayers, photopatternable organic and metal-organic polymers were synthesized. Achieved polymeric platform, being mechanically adaptable, provides possibility of a gentle automatic attachment and subsequent release of active micro-scale devices. Equipped with integrated electronic the platform provides an interface to the neural tissue, confining neural fibers and, if necessary, guiding the regeneration of the tissue with a minimal impact. The self-assembly capability of the platform enables the high yield manufacture of three-dimensionally shaped devices that are relying on geometry/stress dependent physical effects that are evolving in magnetic materials including magentostriction and shape anisotropy. Developed arrays of giant magnetoimpedance sensors and cuff implants provide a possibility to address physiological processes locally or distantly via magnetic and electric fields that are generated deep inside the organism, providing unique real time health monitoring capabilities. Fabricated on a large scale shapeable magnetosensory systems and nanostructured materials demonstrate outstanding mechanical and electrical performance. The novel, shapeable form of electronics can revolutionize the field of mechanical prosthetics, wearable devices, medical aids and commercial devices by adding novel sensory functionalities, increasing their capabilities, reducing size and power consumption.

In this present work, three different classes of fluorescent dyes were characterized, photophysically at the nano scale or at the macro scale, and were further explored to be used as sensors and emissive materials. All nanoscale studies were achieved synthesizing several polymeric micro and nanoparticles doped with two different classes of complexes, boron(III) and platinum(II) and using several polymer matrixes. The first dopant system was based on boron difluoride complexes, varying their alkyl side chain while the chosen polymer matrixes were poly(methyl methacrylate) (PMMA), polyvinylpyrrolidone (PVP) and polystyrene-block-polybutadiene-block-polystyrene (SBS co-polymer). The polymer matrixes, as well as the alkyl side chain, were found to influence the emission and the size of the particles. The particles were considered stable during all thermal stability studies at least during a month, with low variation in the emission intensity, showing promising results as temperature-dependent emission materials. Additionally, a comparison was stablished regarding the macro scale that was reported in a previous work. Co-doped particles were synthesized to develop a system to entrap highly hydrophobic drugs that showed interesting results to be explored in dye&drug-delivery. The second dopant system based on platinum(II) complexes was developed exploring the self-assembly and the aggregation-induced emission enhancement properties of a pyridylpyrazolate Pt(II) metallomesogenic system. The synthesis was achieved by formation of oil-in-water droplets similarly to the previous system. Finally, several coumarin-based pyrazolines compounds were characterized as an attempt to design novel stimuli-responsive chromic materials exhibiting non-reversible thermo-, mechano-, solvato- and vapochromic behaviors due to the presence of intermolecular ··· interactions.

A low-cost chemical sensor based on shrink polymer was presented in this paper. Graphene nanoplatelets were self-assembled on the inner surface of microchannel formed by shrink polymer. The low-cost sensor system can give stable and precise results by only consuming 1 μL reagent, demonstrating great advantage over planar sensor. With assistance of self-assembly and shrink polymer, the sensor can be realized in a simple low-cost way.

Conducting polymers are ionic active materials that can perform electro-chemo-mechanical work through redox reactions. The electro-chemo-mechanical coupling in these materials has been successfully applied to develop various application platforms (actuation systems, sensor elements and energy storage devices (super capacitors, battery electrodes)). Similarly, bioderived membranes are ionic active materials that have been demonstrated as actuators, sensors and energy harvesting devices. Bioderived membranes offer significant advantages over synthetic ionic active materials in energy conversion and the scientific community has put forward various system level concepts for application in engineering applications. The biological origins of these material systems and their subsequent mechanical, electrical and thermal properties have served as a key deterrent in applications. This article proposes a novel architecture that combines a conducting polymer and a bioderived membrane into an integrated material system in which the charge gradients generated from a biochemical reaction is stored and released in the conducting polymer through redox reactions. This paper discusses the fabrication and topographical characterization of the integrated bioderived-conducting polymer membrane nanostructures. The prototype comprises of an organized array of fluid-filled three-dimensional containers with an integrated membrane shell that performs energy conversion and storage owing to its multi-functional microstructure. The bioderived membrane is self-assembled into a hollow spherical container from synthetic membranes or bilayer lipid membranes with proteins and the conducting polymer membrane forms a wrapper around this container resulting in a three-dimensional assembly.

One of the most common sensory structures in nature is the hair cell. Examples of hair cells include the inner and outer hair cells in the inner ears of vertebrates, external sensory hairs on the legs of spiders, and neuromasts found along the lateral lines of fish. Recent work by Sarles and Leo demonstrated that self-assembly methods could be used to construct a membrane-based hair cell that responds to a physical disturbance of the hair. An artificial cell membrane (or lipid bilayer) formed at the interface of two lipid-encased hydrogel volumes, serves as the transduction element in the device. In this study, a revised sensor embodiment is presented in which the hair is fixed at its base by the encapsulating polymeric substrate. In addition, a highly elastic, photo-polymerizable aqueous gel (PEGDA, 6000g/mole) is used to further increase the resiliency of the hair and to provide a compliant cushion for the bilayer. These changes yield a considerably more durable hair cell sensor. We perform a series of experimental tests to characterize the transduction element (i.e. the bilayer) and the sensing current produced by free vibration of the hair, and we study the directional sensitivity of this hair cell embodiment by perturbing the hair in three directions. These tests demonstrate that the magnitude of the sensing current (30–300pA) is significantly affected by direction of perturbation, where the largest signals result from motion of the hair in a direction perpendicular to the plane of the bilayer.