Synthesis and Drop-on-Demand Deposition of Graphene Derivative Inks for Flexible Thin Film Electronics

This dissertation presents methods for deposition and post-processing of Graphene-Carboxymethyl Cellulose (G-CMC) and Graphene Oxide (GO) aqueous functional inks using a custom drop-on-demand (DOD) printer to fabricate mechanically flexible, non-transparent and transparent thin film electronic devices. Thin films on flexible substrates find use in lightweight, low profile, and conformable electronic devices. Such devices can include chemical sensors, flexible RFID tags, bioelectronics circuits, lightweight electronics for space systems, and transparent electrodes for optoelectronic systems. The goal of this research project is to provide simple methods for fabrication of these devices using environmentally friendly and easy to synthesize functional inks. Therefore, two graphene based inks are utilized; GO and a novel Carboxymethyl Cellulose (CMC) functionalized aqueous dispersion of Graphene, G-CMC. Proposed functional inks are deposited on treated substrates by DOD printing. Deposited thin films were post-processed by use of a muffle furnace or a pulsed laser system. Furthermore, gold doped G-CMC films and G-Silver Nanoprism (G-AgNP) composite inks were developed to enhance film electrical properties. Inkjet printed films on glass substrates were characterized in terms of their electrical, optical, and mechanical properties. Correlations between film thickness, optical transmittance, and conductivity were investigated. It was possible to deposit homogeneous thin films at 100 nm to 2000 nm thickness. G-CMC films exhibited good scaling of conductance where thicker films had ~ 660 Ω/sq sheet resistance. Gold doped and G-AgNP composite semi-transparent films exhibited enhanced conductance with sheet resistances of ~ 700 Ω/sq at 35% transparency and ~ 374 Ω/sq at 50% transparency, respectively. Laser assisted treatment of samples was conducted to investigate two opportunities; pulsed laser thermal treatment and pulsed laser micromachining on rigid and flexible substrates. Effect of laser parameters was investigated to establish guidelines for thin film thermal treatment and micromachining Finally, novel flexible sensors and circuits were fabricated to demonstrate task driven performance of proposed materials and methods. Based on the presented work, proposed methods and functional inks show promise for fabricating simple electronic devices on flexible and rigid substrates. It is believed that presented advances may benefit industrial fields that require scalable and simple thin film fabrication methods

Updates of Wearing Devices (WDs) In Healthcare, And Disease Monitoring

 With the rising pervasiveness of growing populace, aging and chronic illnesses consistently rising medical services costs, the health care system is going through a crucial change from the conventional hospital focused system to an individual-focused system. Since the twentieth century, wearable sensors are becoming widespread in medical care and biomedical monitoring systems, engaging consistent estimation of biomarkers for checking of the diseased condition and wellbeing, clinical diagnostics and assessment in biological fluids like saliva, blood, and sweat. Recently, the improvements have been centered around electrochemical and optical biosensors, alongside advances with the non-invasive monitoring of biomarkers, bacteria and hormones, etc. Wearable devices have created with a mix of multiplexed biosensing, microfluidic testing and transport frameworks incorporated with flexible materials and body connections for additional created wear ability and effortlessness. These wearables hold guarantee and are fit for a higher understanding of the relationships between analyte focuses inside the blood or non-invasive biofluids and feedback to the patient, which is fundamentally significant in ideal finding, therapy, and control of diseases. In any case, cohort validation studies and execution assessment of wearable biosensors are expected to support their clinical acceptance. In the current review, we discussed the significance, highlights, types of wearables, difficulties and utilizations of wearable devices for biological fluids for the prevention of diseased conditions and real time monitoring of human wellbeing. In this, we sum up the different wearable devices that are developed for health care monitoring and their future potential has been discussed in detail

Bacterial nanocellulose membrane as novel substrate for biomimetic structural color materials: Application to lysozyme sensing

The development of optical biosensors based on structural colors generated by short-range ordered colloidal particles is attracting growing interest due to their non-iridescent and non-fading features. In this study, a biomimetic approach using biopolymers for the various steps of sensor construction is presented. Bacterial nanocellulose (BNC) has many foreseen applications in biomedical engineering because of its biocompatibility, good mechanical strength, and large modifiable surface area. Herein, a novel approach is taken by using functionalized BNC as a substrate to build a molecularly imprinted photonic sensing layer. BNC was modified with polydopamine (PDA), which improved the adhesion and mechanical properties of the BNC substrate while providing simultaneously a black background for color saturation. A molecularly imprinted polymer (MIP) also made of PDA was used to create the recognition sites for the biomarker lysozyme. A monodisperse colloidal suspension of silica particles was first synthesized and used as core of the MIP shell, and then the photonic structure was assembled on the PDA-BNC membrane. The biosensor showed a detection limit of about 0.8nmolL1 of lysozyme in spiked human serum and demonstrated to be selective against cystatin C. These properties, combined with biocompatible, eco-friendly, and low-cost materials, offer a sustainable sensing platform with great potential for healthcare applications.info:eu-repo/semantics/publishedVersio

Methods for immobilizing receptors in microfluidic devices: A review

In this review article, we discuss state-of-the-art methods for immobilizing functional receptors in microfluidic devices. Strategies used to immobilize receptors in such devices are essential for the development of specific, sensitive (bio)chemical assays that can be used for a wide range of applications. In the first section, we review the principles and the chemistry of immobilization techniques that are the most commonly used in microfluidics. We afterward describe immobilization methods on static surfaces from microchannel surfaces to electrode surfaces with a particular attention to opportunities offered by hydrogel surfaces. Finally, we discuss immobilization methods on mobile surfaces with an emphasis on both magnetic and non-magnetic microbeads, and finally, we highlight recent developments of new types of mobile supports

Nanomaterials for Healthcare Biosensing Applications

In recent years, an increasing number of nanomaterials have been explored for their applications in biomedical diagnostics, making their applications in healthcare biosensing a rapidly evolving field. Nanomaterials introduce versatility to the sensing platforms and may even allow mobility between different detection mechanisms. The prospect of a combination of different nanomaterials allows an exploitation of their synergistic additive and novel properties for sensor development. This paper covers more than 290 research works since 2015, elaborating the diverse roles played by various nanomaterials in the biosensing field. Hence, we provide a comprehensive review of the healthcare sensing applications of nanomaterials, covering carbon allotrope-based, inorganic, and organic nanomaterials. These sensing systems are able to detect a wide variety of clinically relevant molecules, like nucleic acids, viruses, bacteria, cancer antigens, pharmaceuticals and narcotic drugs, toxins, contaminants, as well as entire cells in various sensing media, ranging from buffers to more complex environments such as urine, blood or sputum. Thus, the latest advancements reviewed in this paper hold tremendous potential for the application of nanomaterials in the early screening of diseases and point-of-care testing

Advances in Wearable Sensing Technologies and Their Impact for Personalized and Preventive Medicine

Recent advances in miniaturized electronics, as well as mobile access to computational power, are fostering a rapid growth of wearable technologies. In particular, the application of such wearable technologies to health care enables to access more information from the patient than standard episodically testing conducted in health provider centres. Clinical, behavioural and self-monitored data collected by wearable devices provide a means for improving the early-stage detection and management of diseases as well as reducing the overall costs over more invasive standard diagnostics approaches. In this chapter, we will discuss some of the ongoing key innovations in materials science and micro/nano-fabrication technologies that are setting the basis for future personalized and preventive medicine devices and approaches. The design of wire- and power-less ultra-thin sensors fabricated on wearable biocompatible materials that can be placed in direct contact with the body tissues such as the skin will be reviewed, focusing on emerging solutions and bottlenecks. The application of nanotechnology for the fabrication of sophisticated miniaturized sensors will be presented. Exemplary sensor designs for the non-invasive measurement of ultra-low concentrations of important biomarkers will be discussed as case studies for the application of these emerging technologies

Modeling of supramolecular biopolymers: Leading the <i>in silico</i> revolution of tissue engineering and nanomedicine

Abstract The field of tissue engineering is poised to be positively influenced by the advent of supramolecular biopolymers, because of their promising tailorability coming from the bottom-up approach used for their development, absence of toxic byproducts from their gelation reaction and intrinsic better mimicry of extracellular matrix nanotopography and mechanical properties. However, a deep understanding of the phenomena ruling their properties at the meso- and macroscales is still missing. In silico approaches are increasingly helping to shine a light on questions still of out of reach for almost all empirical methods. In this review, we will present the most significant and updated efforts on molecular modeling of SBP properties, and their interactions with the living counterparts, at all scales. In detail, the currently available molecular mechanic approaches will be discussed, paying attention to the pros and cons related to their representability and transferability. We will also give detailed insights for choosing different biomolecular modeling strategies at various scales. This is a systematic overview of tools and approaches yielding to advances at atomistic, molecular, and supramolecular levels, with a holistic perspective demonstrating the urgent need for theories and models connecting biomaterial design and their biological effect in vivo

Stimuli-sensitive hydrogel materials for sensing and drug delivery

The application of stimuli-sensitive hydrogels in the fabrication of smart devices has become increasingly popular with many research groups and industries. In addition to their ability to experience large reversible transitions in their swelling behaviour due to small physiological or environmental changes, they are also often highly biocompatible, versatile and possess a high storage capacity for the immobilisation of biomolecules. Several transduction methods are currently employed for monitoring the swelling response of these materials, frequently these are based on optical and mechanical methods. Electrochemical transduction has not been investigated as thoroughly but would offer significant benefits in terms of direct coupling with microelectronics, reliability and the possibility of mass production of low-cost disposable electrode devices amenable to miniaturisation. This work demonstrates that electrochemical impedance spectroscopy can be used to track hydrogel swelling in response to target analytes. Highly sensitive detection was achieved based on resistance changes of a pH-sensitive hydrogel in response to glucose. As it demonstrated good potential as a sensing platform, the applicability of this system for detecting other analytes which can elicit a pH change and are challenging in terms of limit of detection requirements was subsequently investigated. The hydrogel was modified to detect β-D-glucuronidase, a marker compound for E.coli. Intelligent materials are also highly desirable for controlled drug delivery applications. In comparison with traditional routes of drug administration (i.e. oral and injection methods), on-demand drug delivery offers safer, more effective medical treatment by enabling site-specific administration with on-off regulation in real time. Consequently, the synthesis and characterisation of a novel electroactive hydrogel composite and its potential application in electro-stimulated drug delivery were explored. Finally, numerous strategies were investigated to improve the swelling rate to overcome the slow response time associated with the hydrogel system. A new fabrication route for superporous hydrogels was investigated and shown for the first time to be a viable synthesis method for hydrogel systems which may be limited by pH or templating restrictions. A dramatic reduction in response time, from hours to seconds, was demonstrated. If coupled with impedimetric transduction, rapid, highly sensitive analyte detection could be achieved which would offer significant benefits and advance the application of hydrogels in smart devices

Photonic hydrogel sensors

Hydrogels are an important tools for sensing because of their sensitivity to small adjustments and reactions to physical, biological, and chemical changes. They have been used in wide range of applications such as biomedical fields for drug delivery and in diagnostics. Hydrogel-based systems are a reusable sensing platform to quantify biomarkers in high-risk patients at clinical and point-of-care settings. In this thesis, two fabrication methods have been developed to successfully detect glucose concentration, pH changes and intraocular pressure (IOP). Continuous glucose monitoring aims to achieve accurate control of blood glucose concentration to prevent hypo/hyperglycaemia in diabetic patients. Also, the development of pH changes sensing device is the key to prevent the fatal implications. The Increasing of intraocular pressure (IOP) is the main risk factor for glaucoma, which is the second major source of losing sight in the world. The first method is to developed hydrogel-based sensor by using stamping technique. A novel glucose sensor based on hydrogel with a micro-imprinted hexagonal structure was fabricated here. Our method utilized diffraction properties of a hexagonally photonic microscale concavities to detect the changes in the glucose concentration from 1 mM to 200 mM. In addition, same method was used to design a new pH hydrogel-based sensor with imprinted Fresnel lens. The sensor was able to monitor the pH changes with respond time of 5 minutes. The sensor had pH range from 4.5 to 7 and showed an increase in the sensitivity after 10 days storage in PBS solution of pH 7.4. Also, when the effect of temperature changes was investigated in the study, the temperature effect was negligible in the performance the sensor. The second method is Laser ablation of commercial contact lenses. Initially, CO2 laser (HPC LS 3040) was used to modify the surface properties of the lens at selective areas by creating 1D and 2D patterns. Laser parameters (space gap between the patterns and laser power, and scan speed) were examined to find the optimal laser setting. We managed to improve the wettability properties of the lens by increasing the density of the surface. After that, we engraved two circular micro-channels on the contact lens using CO2 laser (Rayjet laser). Three different lenses were fabricated with various spacing gap between the channels (1 mm, 1.5 mm and 2 mm). The lenses had maximum channel depth of up to 20 µm. By using laser treated lenses, a change in pressure from 12 mmHg to 22 mmHg, normal eye IOP and glaucoma patients IOP, was detect by the lenses. In summary, this thesis presents important findings that can be recommended for application in medical point-of-care diagnostics, implantable chips, and wearable continuous monitoring devices to quantify biomarkers. These methods offer sensing devices that are easy and fast to manufacture, cost effective, fast response and noninvasive sensors