bluuebunny/crossref_metadata_2025 huggingface dataset:
3D Printed Hydrogel-Based Biosensors for Wearable Applications
Authors: Finny Abraham Samuel , Jiang Cindy , Andreescu Silvana
Published: May 2020

The ability to manufacture sensors rapidly and cost-effectively is essential for creating devices that would benefit healthcare, medical diagnostics, environmental monitoring and process industries. Because of the inherent complexity of sensing devices, new fabrication methods are needed to create sensors that could be fabricated in large scale and with high efficiency. Additive manufacturing techniques like 3D printing and 3D bioprinting enable printing of different biomaterials into intricate 3D architectures which could serve as sensing platforms. This presentation will describe the development and optimization of 3D printed hydrogel-based (bio)sensors with incorporated receptor molecules and transduction interfaces. In order to 3D print these sensors, an extrusion-based 3D bioprinter, and a computer-aided designing software were used along with a novel bio-ink formulation, which contains enzymes, catalytic and photoactive properties. The optimum hydrogel composite provided excellent mechanical properties to the printed biosensors enabling them to be used in a wide range of wearable applications. Fabrication and performance characteristics of two types of sensors will be presented: a lactate sensor for measuring physiological activity in sweat and a UV sensor for measuring harmful UV radiation exposure. The proposed sensors are reagent-less and highly portable making them ideal for use as wearable devices and printed biocatalytic platforms for portable bioelectronics. Examples of applications of these additively manufactured sensors for monitoring different analytes will be discussed.

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(Invited) Passive Eccrine Sweat Analysis Technologies; A New Paradigm in Sweat Analytics
Authors: Prasad Shalini , Muthukumar Sriram
Published: May 2020

Wearable electronic monitors hold great promise in helping people to reach their health goals. These increasingly sophisticated devices help the wearers improve their wellness by constantly monitoring their activities and bodily responses. While consumer wearables that are non–sweat based have been useful for monitoring body vital parameters. However, solutions leveraging human sweat are still in the early stages of development. Wearable devices hold the potential to transform some industries most importantly the health care industry.

Wearable sweat based diagnostic biosensors for the detection and monitoring of analytes in transdermal sweat present an intriguing pathway toward improving user health outcomes in an inexpensive and noninvasive manner. Transdermal biosensors have become a more viable option in recent years, due in large part to the miniaturization of conventional sensing mechanisms. Current minimally invasive strategies demonstrate encouraging results in the monitoring of select biomarkers in peripheral blood and interstitial fluid, but these devices are still minimally invasive as they puncture the skin. Current transdermal sweat biosensors require relatively large volumes in a localized region and count on chemically-induced sweating to attain sufficient sample volume. Thus, there exists a challenge in designing wearable sweat-based sensors that can report and quantify biomarkers of interest from low volumes of human sweat in a completely non-invasive yet still cost-effective manner.

In this talk I will present some non-invasive sweat sensing technologies that detect and quantify biomarkers in human sweat.
(Invited) Wearable Electrochemical Sensors for Noninvasive Monitoring of Health
Authors: Liu Hong
Published: May 2020

Wearable electronic devices equipped with physical sensors that can monitor physical activity and vital signs have been commercially available for years. The last several years have witnessed a trend to integrate sensors for electrochemical analysis onto wearable devices that can at the molecular level provide insight into the state of human health for applications such as early diagnostics. Sensors for perspiration glucose monitoring has attracted much attention and has been reported by several researchers owing to the growing worldwide problem of diabetes. We have reported a nonenzymatic wearable sensor for electrochemical perspiration glucose analysis. Multipotential steps are applied on a Au electrode, including a high negative potential step for pretreatment of the sample which produces a localized alkaline condition on the electrode surface, a moderate potential for glucose detection under the alkaline condition, and a positive potential to clean the electrode surface. Fluorocarbon-based materials are coated on the Au electrode for improving the selectivity and robustness of the sensor. A fully integrated wristband is developed for real-time monitoring of perspiration glucose, and uploading the test results to a smartphone app via Bluetooth, as shown in Figure 1. The analytical results are also compared with that obtained using a HPLC-MS.

1. Xiaofei Zhu, Shuai Yuan, Yinhui Ju, Jun Yang, Chao Zhao*, Hong Liu* Water Splitting-Assisted Electrocatalytic Oxidation of Glucose with a Metal Organic Framework for Wearable Nonenzymatic Perspiration Sensing. Anal. Chem., DOI:10.1021/acs.analchem.9b02328.

2. Jian Chen, Xiaofei Zhu, Yinhui Ju, Biao Ma, Chao Zhao,* Hong Liu, * Electrocatalytic Oxidation of Glucose on Bronze for Monitoring of Saliva Glucose Using a Smart Toothbrush. Sensors and Actuators B: Chemical, 2019, 285, 56-61.

3. Xiaofei Zhu, Yinhui Ju, Jian Chen, Deye Liu, and Hong Liu,* Nonenzymatic Wearable Sensor for Electrochemical Analysis of Perspiration Glucose. ACS Sensors 2018, 2018, 3, 1135–1141.
Multi-Arches Structured All-Carbon Aerogels with Super Elasticity and High Fatigue Resistance As Sensitive Wearable Sensors
Authors: Huang Jiankun , Zeng Jingbin , Yan Zifeng
Published: May 2020

Lightweight, conductive and flexible all-carbon aerogels are promising candidates for piezoresistive sensors. Although there are several techniques developed to produce aerogels, the required flexibility and ductility of all-carbon aerogels are yet to be satisfied due to the structure-derived fatigue failure and energy loss. Herein, we present a two-stage solvothermal freeze-casting approach to fabricate multi-arch structured all-carbon aerogel. Our results and calculations reveal that such a multi-arch shaping is enabled by the solvothermal reduction of graphene oxide and unidirectional “bottom-up” ice-crystal growth. Systematic investigations on stress-strain performances indicate that the multi-arch all-carbon aerogel produces anisotropic fatigue-resistive behaviour in both axial and radial directions under 80% strain and exhibits lower mechanical energy loss coefficient (0.03) in the radial direction. Further ball-falling test indicates that the aerogel can rebound the ball (1400 times heavier than the aerogel) in 0.13 s with a fast recovery speed (720 mm s-1). The remarkable mechanical ductility and conductivity endow the aerogel with high-performance piezoresistivities, such as a wide sensing pressure range (1.43~13.56 kPa), tunable linear sensitivity (9.13~7.29 kPa-1) and incremental gauge factor (38~118). The aerogel is processed as a wearable pressure sensor, which can measure tiny pulses and sound vibrations of an adult. The results reveal that it has high sensitivity with fast response (96 ms) and low power consumption (4 mW), demonstrating its potential practicability in monitoring human healthy activity and distinguishing sounds.

Reference

[1] J.Huang, Z.Yan, Adsorption Mechanism of Oil by Resilient Graphene Aerogels from Oil–Water Emulsion.
Langmuir
, 2018, 34(5): 1890-1898.

[2] J. Huang, H. Wang, B. Liang, Etim. J, Y. Liu, Y. Li, Z. Yan, Oriented freeze-casting fabrication of resilient copper nanowire-based aerogel as robust piezoresistive sensor.
Chemical Engineering Journal
, 2019, 364, 28-36.

[3] J. Huang, J. Zeng, B. Liang, Z. Yan, Multi-arches Structured All-carbon Aerogels with Super Elasticity and High Fatigue Resistance as Sensitive Wearable Sensors.
ACS Applied Material& Interface
, Under revision

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(Invited) Eight Channel Microphysiometry Using a Lab on a Chip Microclinical Analyzer
Authors: Miller Dusty R. , Melow Sara Lynn , Cliffel David E.
Published: May 2020

We have built a multianalyte microphysiometer that detects multiple analytes involved in the cellular bioenergetics simultaneously. Monitoring the uptake of glucose and oxygen, and the production of lactate and acid gives a more complete picture of the metabolic processes within the cell than just acidification microphysiometry alone. Metabolic processes such as glycolysis, mitochondrial ATP generation, and glycogenesis are all directly related to the flux of these analytes. Temporal resolution of metabolic responses is much faster than conventional well-plate studies, leading to dynamic metabolic data. Electrochemical sensors are easily adapted into microfluidic formats for microphysiology readouts.

Our newest instrumental designs include a complete overhaul of the microfluidic chambers, screen printed electrodes, and microfluidic pumps, valves, and drivers that will enable easy adoption of this methodology in the development of 3D cell and tissue studies using 8 separate electrochemical measurements at a time. In the first design, 8 separate amperometric sensors are developed using a screen printed electrode with isolated microfluidic channels. In the second design, 4 amperometric sensors are combined with 4 potentiometric sensors using the newly created CH1440 created by CH Instruments. The adaption of this technology to instrumenting organs-on-a-chip is currently underway.
Wearable Electrochemical Sensors for Rapid and on-Site Chemical Threat Assessment
Authors: Hubble Lee John , Wang Joseph
Published: May 2020

First responders, such as law enforcement officers or emergency medical personnel, are often faced with making critical decisions for scene management before knowing the root cause of the incident. Unfortunately, the threat of chemical and biological terror acts remains a growing global concern and when such events occur the timing of chemical and biological information is critical. Therefore, it is imperative that advances be made in bringing rapid chemical analysis directly into the field.

Wearable electrochemical sensors are well placed to fill this technology gap to advance real-time chemical analytics at the point-of-need. The seamless integration of chemical sensors and biosensors within wearable platforms brings the power of laboratory-based chemical analyses directly to the wearer’s body [1]. While the majority of these wearable sensor systems have focused on healthcare and fitness applications, there are growing demands for developing wearable sensor platforms for rapid and on-site chemical threat assessment for a diverse range of forensic, security and defence applications.

To this effect, this presentation will detail recent progress in glove-based wearable electrochemical sensors, where electrochemical sensing modalities are coupled to dexterous and tactile sampling strategies to provide critical chemical information where needed the most [2]. In particular, there will be a focus on the integration of enzymatic biosensors for the detection of organophosphorus chemical threats [3], through to the development of an electrochemical assay for the synthetic opioid fentanyl [4] and subsequent translation to a glove-based wearable platform [5]. Challenges and future prospects for glove-based wearable electrochemical sensors will be discussed in relation to on-site chemical threat assessment applications.

References

[1] Kim, J., Jeerapan, I., Sempionatto, J.R., Barfidokht, A., Mishra, R.K., Campbell, A.S., Hubble, L.J., Wang, J., Wearable bioelectronics: Enzyme-based body-worn electronic devices, Accounts of Chemical Research, 51 (2018) 2820-2828.

[2] Hubble, L.J., Wang, J., Sensing at your fingertips: Glove-based wearable chemical sensors, Electroanalysis, 31 (2019) 428-436.

[3] Mishra, R.K., Hubble, L.J., Martin, A., Kumar, R., Barfidokht, A., Kim, J., Musameh, M.M., Kyratzis, I.L., Wang, J., Wearable flexible and stretchable glove biosensor for on-site detection of organophosphorus chemical threats, ACS Sensors, 2 (2017) 553-561.

[4] Goodchild, S.A., Hubble, L.J., Mishra, R.K., Li, Z., Goud, K.Y., Barfidokht, A., Shah, R., Bagot, K.S., McIntosh, A.J.S., Wang, J., Ionic liquid-modified disposable electrochemical sensor strip for analysis of fentanyl, Analytical Chemistry, 91 (2019) 3747-3753.

[5] Barfidokht, A., Mishra, R.K., Seenivasan, R., Liu, S., Hubble, L.J., Wang, J., Hall, D.A., Wearable electrochemical glove-based sensor for rapid and on-site detection of fentanyl, Sensors and Actuators B-Chemical, 296 (2019) 126422.
(Plenary) From Gene to Device: The Route to Diagnostics in Low Resource Countries
Authors: Hall Elizabeth A. H. , Henderson Cassi , Seevaratnam Dushanth , Pumford Elizabeth , Daly Ronan
Published: May 2020

Infectious diseases remain a major cause of morbidity and mortality in the low income countries. Patients present with fever, which is difficult to diagnose without specialist laboratory tests. This results in presumptive diagnosis and treatment, which may be incorrect. Without tools to identify infection, antibiotic administration is an attractive generic treatment. The situation is similar for non-communicable diseases. Thus, instead of having accurate diagnosis, patients are more often managed based on probability and clinical judgment. The healthcare economics therefore make antibiotic administration an attractive generic treatment, but now antibiotic resistance is so serious that in some regions half the patients with pneumonia do not respond to the first-line antibiotics. There have been numerous attempts to propose low cost diagnostics for LMICs, but when they are produced in high income countries they remain at high cost when taken in the local context. The required biological reagents for a diagnostic is often be the largest proportion of its total cost (eg >80% in the Philippines for a polymerase in a nucleic acid test, and similar price to US/ Europe, despite the average household income being 80-90% lower). We have revisited the ‘unaffordable’ diagnostics and created a novel design that can be manufactured locally, with only basic infrastructure. We have used synthetic biology to design a protein fusion for nucleic acid amplification, that incorporates locally resourced materials and is targeted to easy local production in resource poor areas.

By taking a ‘gene to diagnostic’ approach, a rational design will be discussed for a diagnostic platform that uses a multifunctional fusion enzyme for point-of-care diagnostics. The platform is demonstrated in nucleic acid tests for leptospirosis, dengue and malaria and a device for sarcosine determination in urine presented (as a marker of early-stage prostate cancer). We have the first step towards providing low cost diagnostics in resource poor areas, which could deliver a sustained improvement in healthcare, while also developing the local economy.
(Invited) Nanosurface Fluidic Devices for Electrochemical Sensing and Biosensing
Authors: Mahshid Sara
Published: May 2020

Diagnostics of pathogenic and genetic disease (such as cancer) at the point of need, in particular at early-stage, requires dynamic manipulation and concentration of a small number of target molecules at individual single-molecule level, which currently limit microfluidic technologies. In my lab, we focus on engineering of new approaches in lab-on-chip technology via synergistically combining nanostructured materials with fluidic sample delivery systems to enhance the sensitivity and selectivity of the detection. Nanostructured materials boost the sensor resolution and show higher biochemical sensitivity and selectivity by significant amplification of the detection sites. We investigate 1) fabrication of novel nanostructured platforms based on 3D materials such as gold and 2D materials such as graphene and molybdenum disulfide, 2) integration of nanostructures with fluid sample delivery and biological assays (based on DNA/antibody) and 3) implementation of the device for detection of small molecules, pathogenic disease, and cancer genomics. In this regard, we address fundamental questions including: optimal interface of nanostructures with fluidic devices; target isolation, preparation and concentration in fluidic devices. We have successfully implemented the nanosurface fluidic devices for rapid and quantitative detection of bacteria such as Escherichia coli (E.coli) and Methicillin-resistant Staphylococcus aureus (MRSA), electrochemical detection of small molecules such as Dopamine and optical detection of extracellular vesicles (EVs).
Adsorption and Desorption of Gas Molecules on SnO2 Material for Temperature-Modulation of Mos Sensors
Authors: Guo Xing-Min
Published: May 2020

Gas sensors with MOS for the detection of toxic explosive gases have been intensely investigated due to their ease of operation, low cost and nice sensitivity. As the materials of MOS, SnO2 has gained particular attention owing to its outstanding sensitivity, high conductivity and chemical stability, but the poor selectivity is still a worst disadvantage for use of SnO2-based gas sensors. In this work, we try to improve the selectivity via temperature-modulation that the sensing cell and the heating cells are integrated to be a sensor, gas molecules is distinguished at different temperature according to dynamic difference of gas molecules adsorption on sensing materials. As a base, effect of adsorption and desorption of CO and H2 on the response is investigated during the process of temperature change. The result was as shown in Fig.1 that adsorption and desorption of H2 molecules on SnO2 materials had been a dynamic equilibrium in temperature range from 300oC, 350oC to 400oC, in which at 350oC H2 molecules were adsorbed most more on thermodynamics, and the rate of adsorption and desorption of H2 molecules was controlled by diffusion of gas molecules on dynamics. This provides an experimental base to improve the sensing characteristics of SnO2 materials.

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(Invited) Role of Surface p-n Heterojunctions in the Gas Sensing with Smox Based Devices - Operando Studies Insights
Authors: Barsan Nicolae
Published: May 2020

Resistive gas sensors based on semiconducting metal oxides (SMOX), such as SnO2, WO3 and In2O3, are widely applied for the detection of flammable or toxic gases such as hydrogen, methane or carbon monoxide. Because of their good sensitivity and stability, simplicity of use, low power consumption, ease of integration and low cost they are also obvious candidates to provide the IoT with the sense of smell. In their pristine form they have, however, inherent disadvantages such as strong interference with water vapour and poor stability. To overcome them, the semiconducting oxides are loaded with catalytically active metals, such as Pd, Pt, Rh or Au; this procedure is often referred to as doping. The understanding of the way in which these additives are impacting the sensor performance is crucial for the further improvement. The models that are generally used were established more than 25 years ago and are not in line with the wealth of new information acquired by applying the newest investigation approaches.

This contribution discusses the different chemical and electrical sensitization mechanisms of noble metal additives by examining their impact on the reception and transduction functions of the gas sensors. Based on state-of-the-art experimental findings, it revises and updates the concepts that are used to explain the mechanisms through which the additives influence the performance of typical gas sensing materials, i.e., oxide nanoparticles arranged in a porous layer. It will explain the differences between doping and loading and the importance of the accurate determination of their chemical state. It will also show how the chemical and electrical contributions to the sensitization are mutually influencing each other and the complex way in which they impact the sensing properties. It will also demonstrate that the understanding of the complex role of additives provides the basis for a knowledge-based design of gas sensors based on semiconducting metal oxide nanoparticles.

Experimental results obtained with the help of various operando investigation techniques will be presented and interpreted with the help of novel mechanistic concepts for the exemplary cases of SnO2:Au,Pt and WO3: Rh, Pd, Pt..
Metal Oxides Hetrostructure: An Efficient to NO2 Gas Detection
Authors: Patil Vikas B
Published: May 2020

A global environmental pollution has become serious problem, due to extensive automobile density and industrialization deeds where destructive as well as poisonous gases like hydrocarbons, carbon monoxide and nitrogen oxides in the surrounding are being extremely used. Nitrogen dioxide (NO2) gas is a usual contaminant in air, in general formed through the power plants, combustion in industrial factories and automotive engines etc. As per health and safety guidelines concern human should not be in contact to 3 ppm exposure of NO2 gas for the time more than 8 hr as its poisonous character can consequence into deterioration and olfactory paralysis. Thus, it is essential to develop sensitive, cost-effective, selective, and trustworthy sensor for the finding of extremely crouch concentration of poisonous NO2 gas.

A metal oxide semiconductors (MOS) such as zinc oxide (ZnO), copper oxide (CuO), tungsten oxide (WO3), iron oxide (Fe2O3), tin dioxide (SnO2), Nickel oxide (NiO) and chromium oxide (Cr2O3) etc., have been widely addressed as sensor resources for NO2 gas due to their high sensitivity, reproducible and stability in idiom of gas response. Conversely; MOS gas sensors normally have their difficulty in disgraceful selectivity, nevertheless; change in resistance of the sensor caused by gas species, which assembles it unachievable for a sensor to precisely identify the gas molecules. Such selectivity and other central gas sensing recital of chemiresistive type MOS gas sensors can be enhanced through the amalgamation of metal oxide semiconductors. Spaced out from the MOS p-type CuO and n-type ZnO are immensely concerned in gas sensing assert due to their effortless synthesis, tailorable electrochemical properties, cost-effectiveness and eco-friendly signature too.

Here, a CuO nanoparticle (NPs) - ZnO nanowire (NWs) hetro-structure gas sensors have been developed by easy, catalyst free thermal evaporation (TE) technique, followed by annealing in different atmosphere such as argon and air. The crystal structural, surface morphological and gas sensing measurements of hetrostructure sensors were studied and reported. At optimized temperature of 150 °C, the hetero-structure sensors express a superior response up to 175% to concentration of 100 ppm NO2 gas. As synthesized hetro-structure sensors, responds to an enormously squat (1 ppm) disclosure of NO2 gas.

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(Invited) Trace Level Detections By Surface-Enhanced Raman Scattering
Authors: Zhang Zhengjun
Published: May 2020

The Raman signals of molecules attached on the very surface of noble metals nanostructures can be greatly enhanced due to the enhancement of the local electric field, by the localized surface plasmon resonance of the nanostructures incident by the laser beam. Therefore, one can make Raman scattering a powerful means in recognizing and quantifying molecules at trace levels. This, however, relies on the sensitivity, stability, etc., of the nanostructures which are used as the substrate surface-enhanced Raman scattering (SERS), and also, the methodologies to quantify the molecules, which are quite difficult even for normal Raman scattering.

We report here, our attempts to design and fabricate silver nano rods as substrate for surface-enhanced Raman scattering, with very high sensitivity, thermal and chemical stability, excellent reusability, etc., by glancing angle deposition techniques with an e-bam system, and covering the surface of the silver nano rods completely by atomic layers deposition of Al2O3 with a thickness of ~ 1.0 nm. These nanorods could be thermally stable in morphology and performance as the SERS substrates up to higher than 400 oC, and chemically stable in harsh environments. These makes the covered Ag nanorods applicable in real environments as SERS substrates. based on the principle component analysis (PCA), we also developed qualitative and quantitative analysis methodologies to quantify chemicals or molecules in complex systems even at trace levels by SERS. Several examples will be shown for trace level analysis of real samples by surface-enahnced Raman scattering with the substrates we designed and fabricated and the approaches we established.
Micro-Spherical ZnSnO3 Material Prepared By Microwave-Assisted Method and Its Ethanol Sensing Properties
Authors: Xu Jiaqiang , Cheng Zhicxuan , Zhang Dan
Published: May 2020

Monodispersed ZnSnO3 microspheres are successfully prepared via a facile microwave-assisted method combing with subsequently calcination treatment process. Powder X-ray diffraction (PXRD) results indicate that the structure of the products evolved from crystalline to amorphous with high-temperature treatments. Field emission scanning electron microscope (FESEM) and the transmission electron microscope (TEM) observations demonstrate that the as-obtained products are composed of uniform microspheres with rough surfaces and the mean diameter is measured as ~700 nm. Moreover, the morphology of ZnSnO3 microspheres can be well controlled by adjusting the ratio of Zn2+ and Sn4+. The gas sensing properties of ZnSnO3 microspheres with different ratios of Zn2+/Sn4+ are investigated. Our results indicate that the ZnSnO3 microspheres exhibit good selectivity and high sensitivity towards ethanol at the optimum working temperature of 230oC. When the sensor is exposed 50 ppm ethanol, the value of response reaches 47 and the response/recovery times are 11 s and 12 s, respectively.

Figure 1
Niobium Pentoxide Nanorods for the Determination of Dissolved Oxygen in Aqueous Media
Authors: Cadorin Martina , Ortega Vega Maria Rita , Ticona Arenas Leliz , de Fraga Malfatti Célia
Published: May 2020

Niobium oxides are a group of materials with great potential for applications within various research fields. The wide variety of Nb-O bonds, structures and allotropic forms results in unique properties, extensively described in literature as catalyst for various chemical reactions. Since this material has shown itself promising for catalytical applications, the goal of this study was to investigate its performance for the fabrication of a sensor device for the electrochemical determination of dissolved oxygen, which is of fundamental importance in areas such as environmental monitoring. Thus, a hydrothermal synthesis was used to obtain the niobium oxide and samples that, beyond the hydrothermal process, underwent calcination heat treatment, were compared. The obtained niobium oxides were morphologically analyzed through SEM and Raman spectroscopy. The hydrothermal synthesys produced amorphous niobium pentoxide nanorods, while the calcination heat treatment resulted in crystalline niobium pentoxide. The electrochemical behavior was studied through cyclic voltammetry and the pH effect over the oxygen reduction reaction was taken into consideration. The amperometric response of the sensor between the working electrode and a saturated calomel reference electrode was measured in a 0,5 M lithium perchlorate (LiClO4) solution. Results have shown that the synthesized niobium pentoxide is a promising material for the determination of the dissolved oxygen in aqueous media since it showed and electrocatalytic activity towards the oxygen reduction reaction. The amperometric response has shown itself linearly related to the concentration of the dissolved oxygen and detected concentrations below 1mg/L.
Formaldehyde Gas Sensor Based on Melamine Foam and Tin Dioxide Composites
Authors: Xu Jiaqiang , Cheng Zhixuan , Li Yuxi
Published: May 2020

Formaldehyde (HCHO) is a volatile organic compound (VOC). It can caused great harm to human and environment. Since the increasing concerns of this problem, to develop effective methods to detect this toxic and hazardous gas has become more and more important , which play an important role in personal safety and environment protection. In this study, melamine foam and tin oxide composites were prepared by in-situ growth and subsequent treatment by using a simple hydrothermal reaction. The morphology, structure and sensing properties of the composites were systematically studied. The results show that tin oxide nanoparticles can grow well on the melamine foam skeleton through a simple hydrothermal reaction and has a good stable morphology. It is found that the three-dimensional spherical/skeletal composite material has better gas sensitivity and selectivity to formaldehyde gas than the pristine tin dioxide under a suitable concentration. The response of the composite to 5 ppm formaldehyde gas can reach 30.0 at 120°C. The reactant of formaldehyde on the surface of the material was studied by in situ IR. At the same time, melamine foam has a certain flexibility, which will have a good development for flexible, miniaturized and wearable formaldehyde sensor.

Keywords：melamine foam plastics；tin oxide；formaldehyde；gas sensor

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Facile Electrochemical Routes for the Composite Coating on Au Inverse Opals As Highly-Sensitive Enzyme-Free Biosensors
Authors: Chung Wei-An , Hung Pei-Sung , Chou Shih-Cheng , Wu Chieh-Jui , Wu Pu-Wei
Published: May 2020

The highly sensitive detection of hydrogen peroxide (H2O2) is of practical importance due to its involvement in the biofunction and signal transduction of cells. Various electrochemical techniques have been explored and studied for its detection, which can be realized through either enzymatic or non-enzymatic sensors. Particularly, non-enzymatic biosensors have been in great demand because of their high stability, high reproducibility, and less susceptible to environmental factors compared to the enzyme-based approach. However, many of them display inferior sensitivity or poor selectivity. Hence, this work aims to develop a highly sensitive non-enzymatic biosensor through structural and compositional approaches. From a structural point of view, Au inverse opals are utilized as the sensor scaffold due to their intriguing porous structure. The spatial arrangement of these materials resembles a honeycomb structure, which provides a high specific surface area, efficient mass transport, and strong mechanical stability. In addition to the benefits brought by inverse opals, we further incorporate a composite coating based on Cu2O to decorate the scaffold surface. Through the combination of a well-ordered pore structure with additional functionalization by composite formation, a synergistic improvement could be realized. To fabricate such structural biosensors, an expedited self-assembly process exploiting electrophoresis technique is first adopted to produce a colloidal crystal template. Subsequent electrodeposition processes are performed to construct the Au inverse opals and relevant functional coatings. The sensing performance of these 3D sensors is then evaluated by the detection of H2O2 using cyclic voltammetric analysis. Their structural and compositional characterizations are conducted by SEM, EDX, XPS, and Raman spectroscopy.
Synthesis and Characterization of Reduced Graphene Oxide Supported Ag/PANI Nanocomposite As Electrochemical Sensor for the Detection of Selected Toxic Heavy Metals
Authors: Woldegebriel Belay Minase
Published: May 2020

Reduced graphene oxidesupported Ag/PANI nanocomposite electrochemical sensor was synthesized through electrochemical methods from electrochemical polymerization of 0.2M aniline monomer in 1M HClandelectrodeposition of silver nanoparticles from AgNO3on a reduced graphene oxide modified bare electrode. The as synthesized(Ag/PANI/RGO) nanocomposites modified electrodewas further characterized by Cyclic Voltammetry. The results show that Ag/PANI/RGO nanocomposite was the highest electroactive substrate than PANI and PANI/RGO. This isdue to reduced graphene oxide and synergetic effects as well as electrocatalytic properties of silver nanoparticles. Forcomparing and as well as forspectroscopic characterization; PANI, PANI/RGO and Ag/PANI/RGO nanocomposites were synthesized by chemical precipitation methods using APS, (NH4)2SO4 as an oxidant and characterized by CV, FTIR, SEM, XRD and UV-Vis and the results showed that a comparable electrochemical properties, optical and structural properties and uniform distribution of silver nanoparticles on the surface of PANI/RGO were observed on SEM micrographs. Fast electron transfer properties werecalculated from standard rate constantfor electrochemically and chemicallysynthesized(Ag/PAN/RGO) nanocomposite sensor werekoof 71.3x10-3s-1and 63.9x10-3s-1, respectively. This (Ag/PANI/RGO) nanocomposite electrochemical sensor was carefully tested with the help of anodic stripping voltammetric process as results; linear regression coefficient (R2) of 0.9990 and 0.9977 for Pb2+ and Cd2+, respectively, were obtained. The results have shown that for surface water, specifically for Cd has higher valuethan the WHO (2008) recommended maximum admissible limits. This is an indication of pollution hazards and weak drinking water treatment practices in the areas, which in turn have important human health implications. Therefore, the government and other responsible authorities to take appropriate corrective measures.
Fast Screening of Pesticides By Raman Spectroelectrochemistry Based on EC-SERS Effect
Authors: Fanjul Pablo , Ibáñez David , Junquera-Pérez Alejandro , González-García María Begoña , Hernández-Santos David
Published: May 2020

Electrochemical Surface-enhanced Raman spectroscopy (EC-SERS) effect is an outstanding procedure that ensures the enhancement of Raman signal, a careful control of the nanostructures prepared and the possibility of detecting different analytes while the substrate preparation is taking place. Development of novel EC-SERS procedures provide these benefits in the simultaneous preparation and measurement process [1,2], and open new gates for analytical applications. Activation of metallic screen-printed electrodes (SPEs) by electrochemical routes leads to the generation of reproducible nanostructures with excellent SERS properties. In that way, gold, silver and copper SPEs circumvent the traditional reproducibility limitation and produce the enhancement of the Raman intensity to favor the detection of low concentrations.

In this work, detection of different pesticides was achieved by the development of new electrochemical activation procedures using metallic SPEs as SERS substrates (Figure 1). The obtained results demonstrate that Raman spectroelectrochemistry is a powerful technique for monitoring the levels of pesticides, being this study the previous step in their detection in real samples.

Figure 1. Raman spectrum of thiram obtained during a cyclic voltammetry using Ag SPE.

References

[1] D. Martín-Yerga, A. Junquera-Pérez, M. B. González-García, J. V. Perales-Rondon, A. Heras, A. Colina, D. Hernández-Santos, P. Fanjul-Bolado, Electrochim. Acta 264 (2018) 183-190.

[2] D. Ibáñez, A. Junquera-Pérez, M. B. González-García, D. Hernández-Santos, P. Fanjul-Bolado, Talanta 206 (2020) 120190.

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Deciphering Plant Signaling Pathway with Semiconducting Single-Walled Carbon Nanotubes
Authors: Lew Tedrick , Strano Michael
Published: May 2020

As a consequence of their sessile nature, plants have developed complex signaling mechanisms to cope with the highly dynamic environment that they live in. In response to external stimuli, plants can utilize various signaling pathways for intercellular communication to engage different metabolic and genetic machineries involved in the plant defense system. Among the many signaling molecules recently uncovered, hydrogen peroxide (H2O2) represents one of the most versatile signaling molecule in plants in response to environmental stresses such as mechanical wounding. Here, we develop an optical nanosensor platform using DNA-wrapped semiconducting single-walled carbon nanotubes (SWNT) to monitor the wound-induced H2O2 signaling pathway in plants. This approach enables non-destructive, real-time detection of changes in endogenous H2O2 level in plants at a remote distance with portable and inexpensive electronics. We demonstrate the versatility of this method to investigate the dynamics between H2O2 and electric signalling pathways in different vegetable crops and plant species. The reversibility of the sensor in vivo and its use to monitor insect feeding for agricultural applications are also demonstrated. In addition, we also developed an auto-propagating wave model to explain the propagation dynamics of H2O2 post-wounding. This newly developed tool offers new opportunities to understand plant defense responses as well as to monitor crop health in real time.
Ceramic Additive Manufacturing for the Rapid Prototyping of Mixed Potential Electrochemical Sensors
Authors: Tsui Lok-kun , Benavidez Angelica D , Garzon Fernando H
Published: May 2020

Ceramic electrochemical sensors play a major role in chemical analysis of gas species, and mixed potential sensors are attractive for their robustness in harsh environments such as automotive exhaust gases. A major challenge for rapid prototyping of ceramic chemical sensors is the high cost, high material waste, and low geometric flexibility of traditional screen printing and tape casting methods. While these two methods are suitable for mass production of thousands to millions of devices, they tend to be cost prohibitive for small scale rapid prototyping applications. Additive manufacturing techniques enable greater flexibility in working with small batches of materials, customized geometry, and shorter turnaround time.

We will discuss efforts in the additive manufacturing of ceramic mixed potential sensors by extrusion of ceramic and conductor pastes onto zirconia laminates. [1] We evaluated the sensor performance to various test gases at the 100 PPM level including NOX, NH3, and C3H8, observing responses on the order of mV/100 ppm. Electrochemical techniques were employed to probe the effects of porosity on sensor response and evaluate the reproducibility of AM techniques. Finally, we will report on the printing of a ceramic gas sensor by extrusion of a ceramic paste to form the substrate instead of using a laminate substrate to demonstrate a complete device can be produced by AM techniques only.

[1] Tsui, L.K.; Benavidez, A.; Evans, L.; Garzon, F.G. Prog. Additive Manuf. 2019, 4, 1, 13-21
Cheap and Simple Optical Anodic Stripping Voltammetry with Closed-Cell Bipolar Electrodes for Sub-Ppb Detection of Lead in Drinking Water
Authors: Fahrenkrug Eli
Published: May 2020

Aging infrastructure has spurred elevated levels of heavy metals in drinking water across the United States. Individual and community access to reputable home tests have been stymied by the expense, limited portability, and impracticality of many existing testing technologies. We developed a new low-cost closed-cell bipolar electrochemical technique that couples conventional anodic stripping voltammetry with on-chip optical readout to a cell phone device in an inherently parallelized fashion. This presentation will introduce the sensing scheme which couples a cathodic electrochemiluminescence (ECL) reaction at one pole of the bipolar electrode with an anodic stripping event at the opposite pole. When the chip is operated in a close-cell bipolar format, near 100% Faradaic efficiencies can be achieved. Electrochemical implications of both the physical chip design and the electrolyte composition on the sensor functionality will be described. Detailed electrochemical characterization of the Ru(bpy) ECL reaction system will also be highlighted. More recent efforts towards replacing ECL readout with an all solid-state transduction mechanism will also be mentioned, with an emphasis on significantly increasing the analysis precision and chip reusability while achieving detection limits in the sub part per billion range.
Nonenzymatic Hydrogen Peroxide Electrochemical Sensor Based on Inkjet-Printed Reduced Graphene Oxide
Authors: Shamkhalichenar Hamed , Choi Jin-Woo
Published: May 2020

The vital role of hydrogen peroxide (H2O2) in many enzyme-catalyzed reactions, has attracted much interest to develop novel approaches for accurate and fast detection of this simple compound [2]. Also, the determination of the hydrogen peroxide level is essential in food processing, environmental analysis, and clinical diagnosis [2]. Reduced graphene oxide (rGO) has shown to be a superior electrode material for electrochemical analysis due to its high electron transfer rate and active surface area [3]. However, the fabrication of such rGO-based electrodes involves complicated and expensive fabrication processes. Herein, we present a disposable, simple, and low-cost H2O2 electrochemical sensor based on rGO for amperometric detection of hydrogen peroxide concentration.

First, the rGO ink material was prepared by mixing 10 ml of graphene oxide (GO) solution with 10 ml of DI water, and sodium dodecyl sulfate (2 mg/ml). The SDS works as a surfactant and reduces the possibility of printer nozzle clogging. The solution was sonicated for 30 minutes and was loaded to a cartridge of an office inkjet printer. To achieve a thicker layer of GO, the printing process was repeated 25 times on a PET film. Next, the electrodes were placed inside hydroiodic (HI) acid for 24 hours at 100 oC to remove oxygenated groups from GO molecular structure. The color of the electrodes became darker after the GO was reduced to rGO (Figure 1.A). Then, the printed pattern was sliced into 20 by 2.5 mm electrodes, and the resistance of the electrode was measured to validate the reduction process.

The step voltammetry method was adopted to measure the H2O2 inside 0.1 M PBS buffer. The solution was stirred at 200 rpm, and -800 mV vs. Ag/AgCl was applied to the working electrode. As it is shown in Figure 1.B, after the addition of 100 µM of H2O2, the current increases due to the reduction of H2O2. Finally, the selectivity of the sensor was evaluated against ascorbic acid and glucose.

In summary, the rGO-based electrochemical sensor was fabricated by inkjet printing graphene oxide with a regular office inkjet printer followed by chemical reduction procedure. The sensor was used to determine the hydrogen peroxide level in aqueous solution. Inkjet-printed rGO electrodes can be used for simple and precise measurement of hydrogen peroxide with high selectivity and sensitivity.

References

[1] W. Chen, S. Cai, Q.-Q. Ren, W. Wen, and Y.-D. Zhao, Analyst, 137 (1), 49-58 (2012).

[2] S. Chen, R. Yuan, Y. Chai, and F. Hu, Microchimica Acta, 180 (1-2), 15-32 (2013).

[3] M. Zhou, Y. Zhai, and S. Dong, Analytical chemistry, 81 (14), 5603-5613 (2009).

Figure 1
Indium Tin Oxide for Sensitive Detection of Manganese in Environmentally and Biogically Relevant Samples
Authors: Rusinek Cory Allen
Published: May 2020

Indium tin oxide (ITO) has long been used as an optically transparent electrode for a variety of applications. For sensing, ITO is commonly seen as the working electrode for spectroelectrochemical measurements where spectroscopic measurements are made under electrochemical control. In this work, however, ITO was investigated for its ability to detect manganese (Mn) in both environmentally and biologically relevant samples using cathodic stripping voltammetry (CSV). ITO exhibited superior performance compared to traditionally-used electrode materials such as glassy carbon, platinum, and boron-doped diamond. The ITO physical vapor deposition (PVD) processes were optimized for Mn detection, including substrate heating during deposition and post-process annealing. Crystallographic changes were observed with the <400> orientation showing the most promise towards Mn detection. Characterization was achieved using multiple topographical and electrochemical methods. Charge-selective polymer films were deposited on the ITO surface to investigate increases in selectivity and/or sensitivity. Using various ITO electrode types, limits of detection (LODs) below 1 ppb were obtained in short measurement times (2-3 min) in environmental samples. In bovine whole-blood samples, ITO exhibited comparable results to those obtained with both graphite furnace- atomic absorption spectroscopy (GF-AAS) and inductively coupled plasma-mass spectrometry (ICP-MS). This work expands on the use of ITO and metal oxides as voltammetric electrodes/sensors; the results presented may be applicable to other analytes amenable to detection by CSV.
Optimization of Printing Properties to Fabricate Devices on Ultra-Thin Flexible Ceramic Substrate
Authors: Kirtania Sharadindu Gopal , Riheen Manjurul Ahsan , Sekhar Praveen K.
Published: May 2020

In this work, the optimization of the inkjet printing properties on a new flexible ceramic substrate is reported. Printing parameters like drop spacing, number of printed layer, sintering temperature and sintering time were varied to ensure an electrically conductive and repeatable pattern. The test patterns were printed using silver nanoparticle ink and Dimatix 2831 inkjet printer. Then electrical conductivity, bending, and adhesion tests were performed on the printed samples. The three factor factorial design analysis showed that the number of printed layers, sintering temperature, and sintering time were significant factors affecting electrical conductivity. The optimum printing parameters for the E-Strate substrate were found to be 20 μm drop spacing, three layers of printing, and 300°C sintering temperature for 30 minutes. The measured optimum resistivity was found to be 7.88 μΩ-cm. Repetitive bending, adhesion test, and ASTM tape test were pursued to inspect mechanical stability.
3-D Printed Multifunctional Sensor Platform for Space Applications
Authors: Sultana Mahmooda
Published: May 2020

Nanomaterials offer a unique set of advantages as sensors for space applications. For instance, one and two dimensional materials such as carbon nanotube, graphene and molybdenum disulfide have high surface-to-volume ratio and superior electrical properties, resulting in highly sensitive environmental sensors. In addition, great mechanical, thermal, and electrical stability, as well as radiation hardness due to minute cross-sectional area, make them useful in space applications. Furthermore, lightweight, low power consumption and small size make nanomaterial-based devices suitable for targeted space missions with limited resources. Nanomaterial-based environmental sensors can be used for the in situ detection of neutrals, trace gases, volatile organics and environmental parameters in a wide range of mission architectures, including atmospheric probes, plume flybys on icy or ocean worlds such as Enceladus or Europa, and landed missions. For example, the multifunctional sensor platform can detect trace gases that can fingerprint various biological and abiotic processes on outer planetary bodies. It can be used to simultaneously detect methane, ammonia and other gases difficult to detect using mass spectrometry due to mass interference issues, and thus can be used in tandem with mass spectrometers. In addition, such a platform can be used for quick screening of samples in sample return missions without adding significantly to the mass and power of the payload. Furthermore, Human exploration missions can benefit from these highly sensitive sensors to detect leaks of toxic gases that are commonly onboard such as hydrazine, ensuring human safety and mission success. This talk will discuss the development of the multifunctional sensor platform with a suite of environmental nanosensors fabricated with additive manufacturing techniques, the performance of the sensors and their applicability to space missions.