Development of a Perchlorate Chemical Sensor Based on Magnetic Nanoparticles and Silicon Nitride Capacitive Transducer

We report in this work the development of a novel capacitance electrochemical sensors based on silicon nitride substrate (Si₃N₄) chemically modified with a structure of Cobalt phthalocyanine, C,C,C,C‐tetracarboxylic acid‐Polyacrylamide (Co(II)Pc‐PAA). This sensitive layer was tested with and without magnetic nanoparticles (MNP) for perchlorate ( ) detection. The developed chemical sensor with Si₃N₄/APTES‐MNP/Co(II)Pc‐PAA structure has shown a better performance when compared to the other structure based on Si₃N₄/Co(II)Pc‐PAA. Contact angle measurements (CAM) and atomic force microscopy (AFM) characterizations have been performed to characterize the functionalization of the chemical sensors surface. Under the optimized structure of the chemical sensor, electrochemical measurements were carried out using Mott‐Schottky analysis for detection within the large range of 10⁻¹⁰ to 10⁻⁴ M with a very low detection limit of 2×10⁻¹⁰ M. The chemical sensor has demonstrated a high selectivity toward when compared to other interfering anions such as Cl⁻, SO₄²⁻, and CO₃²⁻. The present capacitive chemical sensor is very promising for sensitive and rapid detection of for environmental applications.     

Implementation and Characterization of a femto-Farad Capacitive Sensor for pico-Liter Liquid Monitoring

An fF-level capacitive sensor, intended for pL liquid measurements, has been fabricated with MEMS technology and successfully characterized. The sensor measures liquid level variations in a microfluidic channel. The sensor’s capacitance varies from 1.5 fF (channel empty) to 12.8fF (channel filled with 63 pL of water). To reliably detect such small capacitance changes, a low noise measurement system, based on a lock-in amplifier, was implemented. The measured sensitivity of the system is 14.1 mV/fF, and the capacitance detection limit is 0.057 aF/Hz^1/2, which corresponds to a volumetric resolution of about 0.22 fL/Hz^1/2.     

光学氧传感器的研制

本文根据氧分子能有效地猝灭金属有机络合物的荧光的原理，研制了一种氧传感器。     

Copper‐based Metal‐organic Framework Applied in the Development of an Electrochemical Biomimetic Sensor for Catechol Determination

In this study, the synthesis and characterization of a Cu‐based metal‐organic framework (MOF) [Cu₃(BTC)₂(H₂O)₃]_n (where BTC=benzene‐1,3,5‐tricarboxylate), known as HKUST‐1, were performed. The Cu‐MOF was applied in the modification of a carbon paste to obtain a biomimetic sensor for the electrochemical determination of catechol. Kinetic assays confirmed that the Cu‐MOF acts as a catalyst for the oxidation of catechol and it can be considered as a catechol oxidase mimetic. Under optimized conditions, the calibration curve for catechol presented a linear range of 8.0×10⁻⁷ to 3.2×10⁻⁵ mol L⁻¹, with detection limit of=1.0×10⁻⁷ mol L⁻¹. The sensor demonstrated good intra‐day repeatability and inter‐electrode reproducibility (relative standard deviations of 3.8 % (n=10) and 4.3 % (n=6), respectively). In the selectivity study, an adequate peak‐to‐peak separation was observed for hydroquinone and uric acid in relation to catechol, demonstrating that this sensor has the potential for use in the simultaneous determination of these compounds. This sensor was successfully applied in the determination of catechol in water samples.     

Molecularly Imprinted Polyresorcinol Based Capacitive Sensor for Sulphanilamide Detection

A molecularly imprinted polymer (MIP) based capacitive sensor for antibiotic detection in drinking water and milk has been developed on a gold coated silicon electrode (Au Electrode). The electrode was fabricated by electropolymerizing monomer resorcinol (RN) on Au surface in presence of sulphanilamide (SN) as a template molecule, to get insulated RN polymer antibiotic composite. The insulation of the polymer film was improved by incubation of electrode in 1‐Dodecanethiol solution. Subsequently MIP sensor was obtained by extraction of SN in ethanol and acetic acid solution. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements were performed for characterization of the developed MIP electrode at different steps of fabrication. The surface morphology of MIP electrode was characterized using atomic force microscopy (AFM), X‐ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x‐ray spectroscopy (EDS). Performance of MIP sensor was evaluated by measuring change in capacitance against varying concentration of SN using EIS. A linear response in the range 1 to 200 μg L^?1 SN was recorded for MIP sensor with a detection limit of 0.1 μg L^?1. The developed MIP sensor exhibited good selectivity towards SN in water and milk with recoveries in the range 92 % to 105 %. The obtained results suggest the usability of MIP based sensor for SN estimation in water and milk samples.     

Pencil‐drawn Paper‐based Non‐invasive and Wearable Capacitive Respiration Sensor

This paper describes a fully‐drawn pencil‐on‐paper based low‐cost capacitive sensor for non‐invasive respiration monitoring. The sensor utilizes the hygroscopic character of the paper to measure the breathing rate and pattern. The adsorption and desorption of water molecules on paper during inhalation and exhalation results in variation in its dielectric constant. This change in dielectric constant during respiration reflects the change in capacitance of the sensor. By interfacing the sensor with the microcontroller, the capacitance data was acquired and transferred to a smartphone through Bluetooth communication. Being a low cost, wearable, non‐invasive and disposable sensor, it holds tremendous potential in healthcare technology and can be commercialized into a viable product for easy‐to‐use diagnostic purpose.     

Capacitive Saccharide Sensor Based on Immobilized Phenylboronic Acid with Diol Specificity

Applied Biochemistry and Biotechnology - A capacitive sensor for saccharide detection is described in this study. The detection is based on selective interaction between diols and...     

一种高透明、可拉伸导电水凝胶的制备及其在电容传感器中的应用

导电水凝胶由于具备良好的电学特性、可调节的机械性能、易于加工性和生物相容性等,是制备柔性电子设备的理想基材。本文使用马来酸与丙烯酰胺作为共聚单体,氯化锂作为导电离子,N,N'-二甲基双丙烯酰胺作为交联剂,使用光引发剂,采用原位光聚合的方式制备了一种导电水凝胶。制得的水凝胶可见光透过率高达93%,最大拉伸形变~380%,导电率最大为12 S/m。鉴于其优异的综合性能,实验中使用导电水凝胶制备了电容传感器并应用于人体活动监测。结果表明,制备的导电水凝胶电容传感器对不同程度的手指弯曲形变和不同力度的手指触碰均表现出灵敏的响应行为,为未来可穿戴柔性电子产品的发展起到了一定的推动作用。     

Biomimetic design of microfluidic manifolds based on a generalised Murray's law

The relationship governing the optimum ratio between the diameters of the parent and daughter branches in vascular systems was first discovered by Murray using the principle of minimum work. This relationship is now known as Murray's law and states that the cube of the diameter of the parent vessel must equal the sum of the cubes of the daughter vessels. For symmetric bifurcations, an important consequence of this geometric rule is that the tangential shear stress at the wall remains constant throughout the vascular network. In the present paper, we extend this important hydrodynamic concept to arbitrary cross-sections and provide a framework for constructing a simple but elegant biomimetic design rule for hierarchical microfluidic networks. The paper focuses specifically on constant-depth rectangular and trapezoidal channels often employed in lab-on-a-chip systems. To validate our biomimetic design rule and demonstrate the application of Murray's law to microfluidic manifolds, a comprehensive series of computational fluid dynamics simulations have been performed. The numerical predictions are shown to be in very good agreement with the theoretical analysis, confirming that the generalised version of Murray's law can be successfully applied to the design of constant-depth microfluidic devices.     

Capacitive Chemical Sensor for Thiopental Assay Based on Electropolymerized Molecularly Imprinted Polymer

A novel capacitive sensor based on electropolymerized molecularly imprinted polymer (MIP) for thiopental detection is described. The molecularly imprinted film as a recognition element was prepared by electropolymerization of phenol on a gold electrode in the presence of thiopental (template). Cyclic voltammetry and capacitive measurements were used for characterization and evaluation of the polymeric film. The template molecules were removed from the modified electrode surface by washing with an ethanol:water solution. The sensor’s linear response range was between 3 and 20 µM, with a detection limit of 0.6 µM. The proposed sensor exhibited good selectivity, reproducibility. Satisfactory results were obtained in the direct detection of real samples.     

Biomimetic Ion Nanochannels as a Highly Selective Sequential Sensor for Zinc Ions Followed by Phosphate Anions

A novel biomimetic ion‐responsive multi‐nanochannel system is constructed by covalently immobilizing a metal‐chelating ligand, 2,2′‐dipicolylamine (DPA), in polyporous nanochannels prepared in a polymeric membrane. The DPA‐modified multi‐nanochannels show specific recognition of zinc ions over other common metal ions, and the zinc‐ion‐chelated nanochannels can be used as secondary sensors for HPO₄^2? anions. The immobilized DPA molecules act as specific‐receptor binding sites for zinc ions, which leads to the highly selective zinc‐ion response through monitoring of ionic current signatures. The chelated zinc ions can be used as secondary recognition elements for the capture of HPO₄^2? anions, thereby fabricating a sensing nanodevice for HPO₄^2? anions. The success of the DPA immobilization and ion‐responsive events is confirmed by measurement of the X‐ray photoelectron spectroscopy (XPS), contact angle (CA), and current–voltage (I–V) characteristics of the systems. The proposed nanochannel sensing devices display remarkable specificity, high sensitivity, and wide dynamic range. In addition, control experiments performed in complex matrices suggest that this sensing system has great potential applications in chemical sensing, biotechnology, and many other fields.     

Wearable Capacitive Pressure Sensor for Contact and Non-Contact Sensing and Pulse Waveform Monitoring

Sensitive and flexible pressure sensors have invoked considerable interest for a broad range of applications in tactile sensing, physiological sensing, and flexible electronics. The barrier between high sensitivity and low fabrication cost needs to be addressed to commercialize such flexible pressure sensors. A low-cost sacrificial template-assisted method for the capacitive sensor has been reported herein, utilizing a porous Polydimethylsiloxane (PDMS) polymer and a multiwalled carbon nanotube (MWCNT) composite-based dielectric layer. The sensor shows high sensitivity of 2.42 kPa⁻¹ along with a low limit of detection of 1.46 Pa. The high sensitivity originates from adding MWCNT to PDMS, increasing the composite polymer’s dielectric constant. Besides this, the pressure sensor shows excellent stability at a cyclic loading of 9000 cycles, proving its reliability for long-lasting application in tactile and physiological sensing. The high sensitivity of the sensor is suitable for the detection of small deformations such as pulse waveforms as well as tactile pressure sensing. In addition, the paper demonstrates a simultaneous contact and non-contact sensing capability suitable for dual sensing (pressure and proximity) with a single data readout system. The dual-mode sensing capability may open opportunities for realizing compact systems in robotics, gesture control, contactless applications, and many more. The practicality of the sensor was shown in applications such as tactile sensing, Morse code generator, proximity sensing, and pulse wave sensing.     

Non-Aqueous Assay System for Phenobarbital Using Biomimetic Bulk Acoustic Wave Sensor Based on a Molecularly Imprinted Polymer

ABSTRACT

A new biomimetic bulk acoustic wave (BAW) sensor based on a molecularly imprinted polymer (MIP) was fabricated and applied for the determination of phenobarbital The MIP was synthesized using phenobarbital as the template molecule and methacrylic acid as the functional monomer by the non-covalent method. In absolute ethanol, the sensor exhibited good selectivity and sensitivity. A linear relationship between 9.0×10^?8 M and 5.0×10^?5 M was revealed. The determination limit was 5.0×10^?8 M. In harsh chemical environments such as high temperature, organic solvent, bases, acids, etc., the sensor still exhibited long-time stability. Satisfactory results of real sample assay were obtained by the proposed method.     

Capacitive Sensor to Monitor Enzyme Activity by Following Degradation of Macromolecules in Real Time

Applied Biochemistry and Biotechnology - A capacitive sensor was developed to analyze the presence and enzymatic activity of a model protease from standard solutions by following the degradation of...     

Sensitive Biomimetic Sensor Based on Molecular Imprinting at Functionalized Indium Tin Oxide Electrodes

We initially report an electrochemical sensing platform based on molecularly imprinted polymers (MIPs) at functionalized Indium Tin Oxide Electrodes (ITO). In this research, aminopropyl-derivatized organosilane aminopropyltriethoxysilane (APTES), which plays the role of functional monomers for template recognition, was firstly self-assembled on an ITO electrode and then dopamine-imprinted sol was spin-coated on the modified surface. APTES which can interact with template dopamine (DA) through hydrogen bonds brought more binding sites located closely to the surface of the ITO electrode, thus made the prepared sensor more sensitive for DA detection. Potential scanning is presented to extract DA from the modified film, thus DA can rapidly and completely leach out. The affinity and selectivity of the resulting biomimetic sensor were characterized using cyclic voltammetry (CV). It exhibited an increased affinity for DA over that of structurally related molecules, the anodic current for DA oxidation depended on the concentration of DA in the linear range from 2×10⁻⁶ M to 0.8×10⁻³ M with a correlation coefficient of 0.9927. In contrast, DA-templated film prepared under identical conditions on a bare ITO showed obviously lower response toward dopamine in solution. It should be noted that potential scanning is a very effective approach for DA extraction, and surface modification of the electrochemical transducer with functional monomers is responsible for the development of MIPs-based highly sensitive biomimetic sensor.     

Development of a Fluorescent Pb2+ Sensor

A real turn‐on : The emission intensity of heterocycle 1 increases upon binding to Pb²⁺. Thus, 1 acts as a small‐molecule “turn‐on” fluorescent sensor for lead. The sensor is highly selective and is functional over a wide range of pH values.

     

Biomimetic piezoelectric quartz sensor for caffeine based on a molecularly imprinted polymer

A piezoelectric quartz sensor coated with molecularly imprinted polymer (MIP) for caffeine was developed. The MIP was prepared by co-polymerizing methacrylic acid (MAA) and ethylene glycol dimethacrylate (EDMA) in the presence of azobis(isobutyronitrile) as initiator, caffeine as template molecule, and chloroform as solvent. The MIP suspension in polyvinyl chloride/tetrahydrofuran (6:2:1 w/w/v) solution was spin coated onto the surface of the electrode of a 10 MHz AT-cut quartz crystal. The sensor exhibited a linear relationship between the frequency shift and caffeine concentration in the range of 1×10^–7 mg mL^–1 up to 1x10^–3 mg mL^–1 [correlation coefficient (r)=0.9935] in a stopped flow measurement mode. It has a sensitivity of about 24 Hz/ln(concentration, mg mL^–1). A steady-state response was achieved in less than 10 min. The performance characteristic of the sensor shows a promising and inexpensive alternative method of detecting caffeine. Surface studies were carried out for the reagent phase of the sensor using SEM, AFM, and XPS analysis in order to elucidate the imprinting of the caffeine molecule. The SEM micrograph, AFM image, and XPS spectra confirmed the removal of caffeine by Soxhlet extraction in the imprinting process and the rebinding of caffeine to the MIP sensing layer during measurement.     

Biomimetic synthesis of a preclavulone a model

A synthetic route to the preclavulone-A (3) analogs 11 and 14 via allene oxide and 2-oxidopentadienyl cation intermediates is described which is based on the proposed biosynthesis of 3.     

Biomimetic photoelectric conversion systems based on artificial membranes

Biological light-driven proton pumps which could transfer light energy to electrical energy have aroused intense interest in the past years.Many related researches have been conducted to mimic this process in vitro because of its potential significant applications.This review describes the progress in biomimetic photoelectric conversion systems based on different kinds of promising artificial membranes.Both biological bacteriorhodopsin and the photosensitive chemical molecules which could be used to achieve...