Fibers and fabrics for chemical and biological sensing

Wearable sensors can be used to monitor many interesting parameters about the wearer’s physiology and environment, with important applications in personal health and well-being, sports performance and personal safety. Wearable chemical sensors can monitor the status of the wearer by accessing body fluids, such as sweat, in an unobtrusive manner. They can also be used to protect the wearer from hazards in the environment by sampling potentially harmful gas emissions such as carbon monoxide. Integrating chemical sensors into textile structures is a challenging and complex task. Issues which must be considered include sample collection, calibration, waste handling, fouling and reliability. Sensors must also be durable and comfortable to wear. Here we present examples of wearable chemical sensors that monitor the person and also their environment. We also discuss the issues involved in developing wearable chemical sensors and strategies for sensor design and textile integration

Integrated Additive and Subtractive Manufacturing of Glass Photonic Sensors for Harsh Environment Applications

Research and development in advanced manufacturing for sensors and devices fabrication is continuously changing the world, assisting to giving sensing solutions in the physical, chemical and biological fields. Specifically, many modern engineered systems are designed to operate under extreme conditions such as high temperature, high pressure, corrosion/erosion, strong electromagnetic interference, heavy load, long reaching distance, limited space, etc. Very often, these extreme conditions not only degrade the performance of the system but also impose risks of catastrophic failures and severe consequences. To perform reliably under these harsh conditions, the materials and components need to be properly monitored and the systems need to be optimally controlled. However, most existing sensing technologies are insufficient to work reliably under these harsh conditions. Innovations in sensor design, fabrication and packaging are needed to address the technological challenges and bridge the capability gaps. Optical fiber sensors have been widely researched and developed for energy, defense, environmental, biochemical and industry sensing applications. In general, optical fiber sensors have a number of well-known advantages such as miniature in size, high sensitivity, long reaching distance, capability of multiplexing and immunity to electromagnetic interference (EMI). In addition, optical fiber sensors are capable of operating under extreme environment conditions, such as high temperature, high pressure, and toxic/corrosive/erosive atmospheres. However, optical fiber sensors are also fragile and easy to break. It has been a challenging task to fabricate and package optical fiber sensors with predicable performance and desired reliability under harsh conditions. The latest advancements in high precision laser micromachining and three-dimensional (3D) printing techniques have opened a window of opportunity to manufacture new photonic structures and integrated sensing devices that deliver unprecedented performance. Consequently, the optical sensor field has quietly gone through a revolutionary transition from the traditional discrete bulk optics to today’s devices and structures with enhanced functionalities and improved robustness for harsh environment applications. Driven by the needs for sensors capable of operating in harsh environments, integrated additive and subtractive manufacturing (IASM) for glass photonics sensor fabrication process has been proposed and developed. In this dissertation, a series of high-performance optical fiber sensors were proposed and fabricated. In addition, several significant sensing measurements (e.g., pressure, temperature, refractive index variation) of the proposed sensors and structures with enhanced robustness were demonstrated in this dissertation. To realize measurement of above parameters, different working principles were studied, including mechanical deflection, light-material interaction and utilizing properties of fluidics. The sensing performance of the fabricated sensors and structures were characterized to demonstrate the capabilities of the developed IASM process on advanced manufacturing of glass photonic sensors with specific geometry and functions, and the realization for information integrated manufacturing purpose

The Development and Biocompatibility of Low Temperature Co-Fired Ceramic (LTCC) for Microfluidic and Biosensor Applications

Low temperature co-fired ceramic (LTCC) electronic packaging materials are applied for their electrical and mechanical properties, high reliability, chemical stability and ease of fabrication. Three dimensional features can also be prepared allowing integration of microfluidic channels and cavities inside LTCC modules. Mechanical, optical, electrical, microfluidic functions have been realized in single LTCC modules. For these reasons LTCC is attractive for biomedical microfluidics and Lab-on-a-Chip systems. However, commercial LTCC systems, optimized for microelectrics applications, have unknown cytocompatibility, and are not compatible with common surface functionalization chemistries. The first goal of this work is to develop biocompatible LTCC materials for biomedical applications. In the current work, two different biocompatible LTCC substrate materials are conceived, formulated and evaluated. Both materials are based from well-known and widely utilized biocompatible materials. The biocompatibilities of the developed LTCC materials for in-vitro applications are studied by cytotoxicity assays, including culturing endothelial cells (EC) both in LTCC leachate and directly on the LTCC substrates. The results demonstrate the developed LTCC materials are biocompatible for in-vitro biological applications involving EC. The second goal of this work is to develop functional capabilities in LTCC microfluidic systems suitable for in-vitro and biomedical applications. One proposed application is the evaluation of oxygen tension and oxidative stress in perfusion cell culture and bioreactors. A Clark-type oxygen sensor is successfully integrated with LTCC technique in this work. In the current work, a solid state proton conductive electrolyte is used to integrate an oxygen sensor into the LTCC. The measurement of oxygen concentration in Clark-type oxygen sensor is based on the electrochemical reaction between working electrode and counter electrode. Cyclic voltammetry and chronoamperometry are measured to determine the electrochemical properties of oxygen reduction in the LTCC based oxygen sensor. The reduction current showed a linear relationship with oxygen concentration. In addition, LTCC sensor exhibits rapid response and sensitivity in the physiological range 1─9 mg/L. The fabricated devices have the capabilities to regulate oxygen supply and determination of local dissolved oxygen concentration in the proposed applications including perfusion cell culture and biological assays

A 3D-printed microfluidic-enabled hollow microneedle architecture for transdermal drug delivery.

Embedding microfluidic architectures with microneedles enables fluid management capabilities that present new degrees of freedom for transdermal drug delivery. To this end, fabrication schemes that can simultaneously create and integrate complex millimeter/centimeter-long microfluidic structures and micrometer-scale microneedle features are necessary. Accordingly, three-dimensional (3D) printing techniques are suitable candidates because they allow the rapid realization of customizable yet intricate microfluidic and microneedle features. However, previously reported 3D-printing approaches utilized costly instrumentation that lacked the desired versatility to print both features in a single step and the throughput to render components within distinct length-scales. Here, for the first time in literature, we devise a fabrication scheme to create hollow microneedles interfaced with microfluidic structures in a single step. Our method utilizes stereolithography 3D-printing and pushes its boundaries (achieving print resolutions below the full width half maximum laser spot size resolution) to create complex architectures with lower cost and higher print speed and throughput than previously reported methods. To demonstrate a potential application, a microfluidic-enabled microneedle architecture was printed to render hydrodynamic mixing and transdermal drug delivery within a single device. The presented architectures can be adopted in future biomedical devices to facilitate new modes of operations for transdermal drug delivery applications such as combinational therapy for preclinical testing of biologic treatments

Microreactor with integrates temperature control for the synthesis of CdSe nanocrystals

The recent needs in the nanosciences field have promoted the interest towards the development of miniaturized and highly integrated devices able to improve and automate the current processes associated to the efficient nanomaterials production. Herein, a green tape based microfluidic system to perform high temperature controlled synthetic reactions of nanocrystals is presented. The device, which integrates both, the microfluidics and a thermally controlled platform, was applied to the automated and continuoussynthesis of CdSe quantum dots. Since temperature can be accurately regulated as required, sizecontrolled and reproducible quantum dots could be obtained by regulating this parameter and the molar ratio of precursors. The obtained nanocrystals were characterized by UV-Vis and fluorescencespectrophotometries. The band width of the emission peaks obtained indicates a narrow size distribution of the nanocrystals, which confirms the uniform temperature profile applied for each synthetic process, being the optimum temperature at 270° C (Full Width at Half Maximum = 40 nm). This approach allows a temperature controlled, easy, low cost and automated way to produce quantum dots in organic media, enhancing its application from laboratory-scale to pilot-line scale processes.This work has been supported by the Spanish Ministry of Science and Innovation (MICINN) through projects CTQ2009-12128 and the Consolider Ingenio 2010 project CSD2006 -12 and Catalonia 15 Government through SGR 2009 -0323

Optimization of fluidic microchannel manufacturing processes in low temperature co-fired ceramic substrates

The processing of starch powder and polymer based sacrificial layer for fabrication of microfluidic structures in low temperature co-fired ceramics (LTCC) is described in the paper. Sacrificial volume material (SVM) was placed into the channel of LTCC sheets to avoid sagging by supporting embedded, three-dimensional structures such as channels, cavities during firing. Sagging of laminated structures is a common problem in the processing of the LTCC. A series of experiments were carried out for different lamination schemes which affect the quality of LTCC sheets. Samples were tested by an acoustic microscope to reveal the internal inhomogeneities and delaminations. As a consequence of burnout, the increased fraction of evolving gases from SVM requires an adequate adaptation of the firing process to provide a residue-free burnout without damaging the structure. Using thermal analysis the intensity of the evaporating gases was determined during co-firing. Based on these results, the modification of the heating p rofile could be done. It is proposed that the fabrication of embedded structures in a multi-layer LTCC platform could be achieved by controlling SVM burnout with a modified heating profile. Using this approach, fabrication of embedded channels in LTCC substrate is demonstrated

Cell Culture on MEMS Platforms: A Review

Microfabricated systems provide an excellent platform for the culture of cells, and are an extremely useful tool for the investigation of cellular responses to various stimuli. Advantages offered over traditional methods include cost-effectiveness, controllability, low volume, high resolution, and sensitivity. Both biocompatible and bioincompatible materials have been developed for use in these applications. Biocompatible materials such as PMMA or PLGA can be used directly for cell culture. However, for bioincompatible materials such as silicon or PDMS, additional steps need to be taken to render these materials more suitable for cell adhesion and maintenance. This review describes multiple surface modification strategies to improve the biocompatibility of MEMS materials. Basic concepts of cell-biomaterial interactions, such as protein adsorption and cell adhesion are covered. Finally, the applications of these MEMS materials in Tissue Engineering are presented.Institute of Bioengineering and Nanotechnology (Singapore)Singapore. Biomedical Research CouncilSingapore. Agency for Science, Technology and ResearchSingapore. Agency for Science, Technology and Research (R-185-001-045-305)Singapore. Ministry of EducationSingapore. Ministry of Education (Grant R-185- 000-135-112)Singapore. National Medical Research CouncilSingapore. National Medical Research Council (Grant R-185-000-099-213)Jassen Cilag (Firm)Singapore-MIT Alliance (Computational and Systems Biology Flagship Project)Global Enterprise for Micro-Mechanics and Molecular Medicin

HIGH PERFORMANCE PIEZOELECTRIC MATERIALS AND DEVICES FOR MULTILAYER LOW TEMPERATURE CO-FIRED CERAMIC BASED MICROFLUIDIC SYSTEMS

The incorporation of active piezoelectric elements and fluidic components into micro-electromechanical systems (MEMS) is of great interest for the development of sensors, actuators, and integrated systems used in microfluidics. Low temperature cofired ceramics (LTCC), widely used as electronic packaging materials, offer the possibility of manufacturing highly integrated microfluidic systems with complex 3-D features and various co-firable functional materials in a multilayer module. It would be desirable to integrate high performance lead zirconate titanate (PZT) based ceramics into LTCC-based MEMS using modern thick film and 3-D packaging technologies. The challenges for fabricating functional LTCC/PZT devices are: 1) formulating piezoelectric compositions which have similar sintering conditions to LTCC materials; 2) reducing elemental inter-diffusion between the LTCC package and PZT materials in co-firing process; and 3) developing active piezoelectric layers with desirable electric properties. The goal of present work was to develop low temperature fired PZT-based materials and compatible processing methods which enable integration of piezoelectric elements with LTCC materials and production of high performance integrated multilayer devices for microfluidics. First, the low temperature sintering behavior of piezoelectric ceramics in the solid solution of Pb(Zr0.53,Ti0.47)O3-Sr(K0.25, Nb0.75)O3 (PZT-SKN) with sintering aids has been investigated. 1 wt% LiBiO2 + 1 wt% CuO fluxed PZT-SKN ceramics sintered at 900oC for 1 h exhibited desirable piezoelectric and dielectric properties with a reduction of sintering temperature by 350oC. Next, the fluxed PZT-SKN tapes were successfully laminated and co-fired with LTCC materials to build the hybrid multilayer structures. HL2000/PZT-SKN multilayer ceramics co-fired at 900oC for 0.5 h exhibited the optimal properties with high field d33 piezoelectric coefficient of 356 pm/V. A potential application of the developed LTCC/PZT-SKN multilayer ceramics as a microbalance was demonstrated. The final research focus was the fabrication of an HL2000/PZT-SKN multilayer piezoelectric micropump and the characterization of pumping performance. The measured maximum flow rate and backpressure were 450 μl/min and 1.4 kPa respectively. Use of different microchannel geometries has been studied to improve the pumping performance. It is believed that the high performance multilayer piezoelectric devices implemented in this work will enable the development of highly integrated LTCC-based microfluidic systems for many future applications

Bio- und Umweltsensorik basierend auf organischer Optoelektronik

The integration of organic light emitting diodes (OLEDs) and organic photodetectors (OPDs) promises compact and low-cost hybrid integrated sensors for optical detection. The thermal evaporation-based device fabrication technique allows for all optical sensing elements being permanently aligned with a high degree of miniaturization, creating more portable, energy-efficient and multiplexing-capable devices; these may be easily combined with microfluidic units resulting in a minimal sample and reagent volume demand of the sensor. This dissertation deals in particular with the system design, development, characterization and deployment of a monolithic integrated sensor unit with 8 OLED and 8 OPD pixel pairs for different applications. The following work provides an extensive study of the system efficiency via ray tracing simulations, investigating crucial boundary conditions for efficient analyte detection. The proposed sensing unit contains OLED and OPD devices with an individual pixel size of 0.5mm × 0.5mm fabricated on a 12.5mm × 12.5mm glass substrate. The developed sensor system was successfully characterized and applied in a biosensing application by detecting fluorescence labelled single-stranded DNA (ssDNA) after forming the Förster resonance energy transfer (FRET) upon the hybridization of two ssDNA strands. This optoelectronic sensor has the potential to enable compact and low-cost fluorescence point-of-care (POC) devices for decentralised multiplex biomedical testing. Additionally, this sensing platform was deployed in environmental and agricultural applications to detect nutrients such as nitrite and nitrate. In this colorimetric application the popular Griess reaction was utilized to form the nitrite concentration dependent amount of azo dye, which absorbs light around 540nm