One-Dimensional ZnO/Gold Junction for Simultaneous and Versatile Multisensing Measurements

The sensing capabilities of zinc oxide nano/micro-structures have been widely investigated and these structures are frequently used in the fabrication of cutting-edge sensors. However, to date, little attention has been paid to the multi-sensing abilities of this material. In this work, we present an efficient multisensor based on a single zinc oxide microwire/gold junction. The device is able to detect in real time three different stimuli, UV-VIS light, temperature and pH variations. This is thanks to three properties of zinc oxide its photoconductive response, pyroelectricity and surface functionalization with amino-propyl groups, respectively. The three stimuli can be detected either simultaneously or in a sequence/random order. A specific mathematical tool was also developed, together with a design of experiments (DoE), to predict the performances of the sensor. Our micro-device allows reliable and versatile real-time measurements of UV-VIS light, temperature and pH variations. Therefore, it shows great potential for use in the field of sensing for living cell cultures

pH-triggered conduction of amine-functionalized single ZnO wire integrated on a customized nanogap electronic platform

The electrical conductance response of single ZnO microwire functionalized with amine-groups was tested upon an acid pH variation of a solution environment after integration on a customized gold electrode array chip. ZnO microwires were easily synthesized by hydrothermal route and chemically functionalized with aminopropyl groups. Single wires were deposited from the solution and then oriented through dielectrophoresis across eight nanogap gold electrodes on a platform single chip. Therefore, eight functionalized ZnO microwire-gold junctions were formed at the same time, and being integrated on an ad hoc electronic platform, they were ready for testing without any further treatment. Experimental and simulation studies confirmed the high pH-responsive behavior of the amine-modified ZnO-gold junctions, obtaining in a simple and reproducible way a ready-to-use device for pH detection in the acidic range. We also compared this performance to bare ZnO wires on the same electronic platform, showing the superiority in pH response of the amine-functionalized material

Micro- and nano-devices for electrochemical sensing

Electrode miniaturization has profoundly revolutionized the field of electrochemical sensing, opening up unprecedented opportunities for probing biological events with a high spatial and temporal resolution, integrating electrochemical systems with microfluidics, and designing arrays for multiplexed sensing. Several technological issues posed by the desire for downsizing have been addressed so far, leading to micrometric and nanometric sensing systems with different degrees of maturity. However, there is still an endless margin for researchers to improve current strategies and cope with demanding sensing fields, such as lab-on-a-chip devices and multi-array sensors, brain chemistry, and cell monitoring. In this review, we present current trends in the design of micro-/nano-electrochemical sensors and cutting-edge applications reported in the last 10 years. Micro- and nanosensors are divided into four categories depending on the transduction mechanism, e.g., amperometric, impedimetric, potentiometric, and transistor-based, to best guide the reader through the different detection strategies and highlight major advancements as well as still unaddressed demands in electrochemical sensing

Solid State Circuits Technologies

The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book

Design and Implementation of an Integrated Biosensor Platform for Lab-on-a-Chip Diabetic Care Systems

Recent advances in semiconductor processing and microfabrication techniques allow the implementation of complex microstructures in a single platform or lab on chip. These devices require fewer samples, allow lightweight implementation, and offer high sensitivities. However, the use of these microstructures place stringent performance constraints on sensor readout architecture. In glucose sensing for diabetic patients, portable handheld devices are common, and have demonstrated significant performance improvement over the last decade. Fluctuations in glucose levels with patient physiological conditions are highly unpredictable and glucose monitors often require complex control algorithms along with dynamic physiological data. Recent research has focused on long term implantation of the sensor system. Glucose sensors combined with sensor readout, insulin bolus control algorithm, and insulin infusion devices can function as an artificial pancreas. However, challenges remain in integrated glucose sensing which include degradation of electrode sensitivity at the microscale, integration of the electrodes with low power low noise readout electronics, and correlation of fluctuations in glucose levels with other physiological data. This work develops 1) a low power and compact glucose monitoring system and 2) a low power single chip solution for real time physiological feedback in an artificial pancreas system. First, glucose sensor sensitivity and robustness is improved using robust vertically aligned carbon nanofiber (VACNF) microelectrodes. Electrode architectures have been optimized, modeled and verified with physiologically relevant glucose levels. Second, novel potentiostat topologies based on a difference-differential common gate input pair transimpedance amplifier and low-power voltage controlled oscillators have been proposed, mathematically modeled and implemented in a 0.18μm [micrometer] complementary metal oxide semiconductor (CMOS) process. Potentiostat circuits are widely used as the readout electronics in enzymatic electrochemical sensors. The integrated potentiostat with VACNF microelectrodes achieves competitive performance at low power and requires reduced chip space. Third, a low power instrumentation solution consisting of a programmable charge amplifier, an analog feature extractor and a control algorithm has been proposed and implemented to enable continuous physiological data extraction of bowel sounds using a single chip. Abdominal sounds can aid correlation of meal events to glucose levels. The developed integrated sensing systems represent a significant advancement in artificial pancreas systems

Electrical and Electro-Optical Biosensors

Electrical and electro-optical biosensing technologies are critical to the development of innovative POCT devices, which can be used by both professional and untrained personnel for the provision of necessary health information within a short time for medical decisions to be determined, being especially important in an era of global pandemics. This Special Issue includes a few pioneering works concerning biosensors utilizing electrochemical impedance, localized surface plasmon resonance, and the bioelectricity of sensing materials in which the amount of analyte is pertinent to the signal response. The presented results demonstrate the potential of these label-free biosensing approaches in the detection of disease-related small-molecule metabolites, proteins, and whole-cell entities

Development of a microfluidic device for gaseous formaldehyde sensing = Développement d\u27un dispositif microfluidique pour la détection de formaldéhyde à l\u27état gazeux

Formaldehyd (HCHO) ist eine chemische Verbindung, die bei der Herstellung einer großen Zahl von Haushaltsprodukten verwendet wird.Charakteristisch ist seine hohe Flüchtigkeit aufgrund einer niedrigen Siedetemperatur ($T = - 19\ ℃$). Daher ist HCOH fast überall als Luftschadstoff in Innenräumen vorhanden. Die Miniaturisierung analytischer Systeme zu Handheld-Gerät hat das Potenzial, nicht nur effizientere, sondern auch empfindlichere Instrumente für die Echtzeitüberwachung dieses gefährlichen Luftschadstoffs zu ermöglichen. Die vorliegende Doktorarbeit präsentiert die Entwicklung eines Mikrofluidik-Geräts für die Erfassung von HCHO basierend auf der Hantzsch-Reaktion.Hierbei wurde der Schwerpunkt auf die Komponente für Fluoreszenzdetektion gelegt. Es wurde eine umfangreiche Literaturrecherche durchgeführt, die es erlaubt, den Stand der Technik auf dem Gebiet der Miniaturisierung des Fluoreszenzsensors zusammenzufassen. Auf Grund dieser Studie wurde ein modulares Fluoreszenzdetektionskonzept vorgeschlagen, das um einen CMOS-Bildsensor (CIS) herum entwickelt wurde. Zwei dreischichtige Fluidikzellenkonfigurationen (Konfiguration 1: Quarz - SU-8 3050 - Quarz und Konfiguration 2: Silizium - SU-8 3050 - Quarz) wurden in Betracht gezogen und parallel unter den gleichen experimentellen Bedingungen getestet. Die Verfahren der Mikrofabrikation der fluidischen Zellen wurden detailliert beschrieben, einschließlich des Integrationsprozesses der Standardkomponenten und der experimentellen Verfahren. Der CIS-basierte Fluoreszenzdetektor bewies seine Leistungsfähigkeit, eine anfängliche HCHO-Konzentration von 10 µg/L vollständig in 3,5-Diacetyl-1,4-dihydrolutidin (DDL- derivatisiert) sowohl für die Quarz- als auch für die Silizium-Fluidikzellen zu detektieren. Beide Systemewiesenein Abfragevolumen von 3,5 µL auf. Ein offensichtlich höheres Signal-Rausch-Verhältnis (SNR) wurde für die Silizium-Fluidzelle ($\text{SNR}_{\text{silicon}} = 6.1$) im Vergleich zur Quarz-Fluidzelle ($\text{SNR}_{\text{quartz}} = 4.9$) beobachtet. Die Verstärkung der Signalintensität in der Silizium-Fluidzelle ist wahrscheinlich auf den Silizium-Absorptionskoeffizienten bei der Anregungswellenlänge zurückzuführen,$a\left( \lambda_{\text{abs}} = 420\ nm \right) = 5 \bullet 10^{4}\text{cm}^{- 1}$. Dieser Koeffizient ist ungefähr fünfmal höher als der Absorptionskoeffizient bei der Fluoreszenzemissionswellenlänge $a\left(\lambda_{\text{em}} = 515\ nm \right) = 9.25 \bullet 10^{3}\text{cm}^{- 1}$. HCHO wird aufgrund seiner relativ hohen Konstanten für das Henry-Gesetz sehr schnell in ein flüssiges Reagenz aufgenommen. Somit hängt die Auswahl des molekularen Einfangverfahrens (Schwallströmung, Ringströmung oder membranbasierte Strömungswechselwirkung) von derLeistungsfähigkeit des Fluoreszenzdetektors ab. Ein vorläufiges Konzept, das auf der Verwendung einer Gas-Flüssigkeitsmembran-basierten Wechselwirkung zum ständigen Abfangen des gasförmigen HCHO basiert, wurde eingeführt. Hierzu wurden kompatible Materialien und Herstellungsmethoden identifiziert. Darüber hinaus wurden CFD-Simulationen durchgeführt, um die Mikrokanallänge unter verschiedenen hydrodynamischen Bedingungen abzuschätzen, die für eine vollständige HCHO-Derivatisierung erforderlich sind. Eine Verbesserung und Vereinfachung auf der Grundlage von sehrnempfindlichen Fluoreszenzdetektoren mit niedrigen Detektionsgrenzen könnte zukünftig basierend z. B. auf Schwallströmung oder Ringströmung möglich sein

Soft and flexible material-based affinity sensors

Recent advances in biosensors and point-of-care (PoC) devices are poised to change and expand the delivery of diagnostics from conventional lateral-flow assays and test strips that dominate the market currently, to newly emerging wearable and implantable devices that can provide continuous monitoring. Soft and flexible materials are playing a key role in propelling these trends towards real-time and remote health monitoring. Affinity biosensors have the capability to provide for diagnosis and monitoring of cancerous, cardiovascular, infectious and genetic diseases by the detection of biomarkers using affinity interactions. This review tracks the evolution of affinity sensors from conventional lateral-flow test strips to wearable/implantable devices enabled by soft and flexible materials. Initially, we highlight conventional affinity sensors exploiting membrane and paper materials which have been so successfully applied in point-of-care tests, such as lateral-flow immunoassay strips and emerging microfluidic paper-based devices. We then turn our attention to the multifarious polymer designs that provide both the base materials for sensor designs, such as PDMS, and more advanced functionalised materials that are capable of both recognition and transduction, such as conducting and molecularly imprinted polymers. The subsequent content discusses wearable soft and flexible material-based affinity sensors, classified as flexible and skin-mountable, textile materials-based and contact lens-based affinity sensors. In the final sections, we explore the possibilities for implantable/injectable soft and flexible material-based affinity sensors, including hydrogels, microencapsulated sensors and optical fibers. This area is truly a work in progress and we trust that this review will help pull together the many technological streams that are contributing to the field

Development of a Wireless MEMS Multifunction Sensor System and Field Demonstration of Embedded Sensors for Monitoring Concrete Pavements, Volume II

This two-pronged study evaluated the performance of commercial off-the-shelf (COTS) micro-electromechanical sensors and systems (MEMS) embedded in concrete pavement (Final Report Volume I) and developed a wireless MEMS multifunctional sensor system for health monitoring of pavement systems (Final Report Volume II). The Volume I report focused on the evaluation of COTS MEMS sensors embedded in concrete pavement sections. The Volume II report covers the set of MEMS sensors that were developed as single-sensing units for measuring moisture, temperature, strain, and pressure. These included the following sensors: (1) nanofiber-based moisture sensors, (2) graphene oxide (GO)–based moisture sensors, (3) flexible graphene strain sensors with liquid metal, (4) graphene strain and pressure sensors, (5) three-dimensional (3D) planar and helical structured graphene strain sensors, (6) temperature sensors, and (7) water content sensors. In addition, the MEMS temperature sensors and the MEMS water content sensors were integrated into one sensing unit as a multifunctional sensor. A wireless signal transmission system was built for MEMS sensor signal readings. Characterization of the sensors was conducted and sensor responses were analyzed using different applications. The sensors developed were installed and tested inside concrete. The results demonstrated the capability to detect sensor response changes at the installed locations