Sensors and Actuators Reports最新文献

In this paper, we study size effects on the reference electrode performance of flexible inkjet printed electrochemical (EC) sensors and present a scheme to print a reliable miniaturized Ag/AgCl(s) electrode for biomedical device applications. The newly printed electrode only with a size of 6900 μm², i.e., equivalent to 83 × 83 μm² can perform as well as the commercial one. Experimental results show the electrode impedance is effectively reduced via the incorporation of graphene flakes into the ionic liquid-based PVC film coated on the electrode to accelerate the ion-transferring rate of the chloride ions, thereby facilitating rapid chloride ion redistribution for the film to reach a quick potential balance with the reference electrode for open circuit potential (OCP) measurement. The EC sensors using the reference electrode can exhibit a fixed OCP output with a low potential variation, quick response time and potential drift, which are ±2.1 mV variant, 50 s, and 23.5 μV/h, respectively regardless of the concentration of chloride ions in the tested environment.

Nafion®-nanostructured polyaniline (nsPANi) composite film is prepared using cyclic voltammetry (CV) and immobilized with creatinine deiminase (CD) enzyme and is used to sense creatinine in a buffer phosphate solution. The conditions for preparing Nafion®-nsPANi composite film are optimized by using a mixture design for which the sensitivity is the response. The relationship between the sensitivity of the amperometric creatinine biosensor (y) and the normalized aniline concentration (Y₁), HCl concentration (Y₂) and scanning rate (Y₃) is y = 119.44Y₁ + 45.23Y₂ + 100.93Y₃ + 255.69Y₁Y₂ + 313.16Y₁Y₃ + 430.56Y₁Y₂Y₃

The maximum sensitivity of an amperometric creatinine biosensor that is constructed using Nafion®-nsPANi composite film in 0.0943 M aniline, 0.9024 M HCl and using a scanning rate of 27.88 mV s ^− 1 is 2013.2 μA mM⁻¹ cm⁻², which is 54.9% better than the sensitivity of a conventional experimental technique. The amperometric creatinine biosensor is 6.60% less sensitive after sensing 0.15 mM creatinine 240 times. The amperometric creatinine biosensor incurs insignificant interference in 0.138 mM urea, 0.085 mM ascorbic acid (AA) and 5.54 mM glucose.

Molecularly imprinted polymer (MIP)-based electrochemical sensors have received growing attention over past decades owing to its robust nature, simple electrochemical control for template removal and cavity regeneration, and go-as-you-please cavity designs into various geometries specific to target analytes. The strength of MIP scheme, in combination with the advantages of electrochemical sensing techniques such as operation simplicity, rapid response, and high sensitivity, provide a synergistic effort to form a highly effective sensing platform suitable for an extremely wide range of interest. In this Review, the introduction of MIP and the comparison between electrochemical sensing methods and other detection strategies are briefly discussed. Then, a broad range of analytes determined using MIP-based electrochemical sensors are listed and critically reviewed, mainly focusing on the applied electrochemical technique, presented linear range along with limit of detection (LOD), biological fluid used in real testing, and pretreatment for real sample. Other sensor performances like selectivity towards analyte, signal repeatability, sensor-to-sensor reproducibility, and stability, are carefully compared with other reported papers. MIP sensors fabricated via the nanoMIP technology, and the ones integrated with portable analyzers, are given in more details as good results are always observed in such instances. Finally, a conclusion regarding recent advances on MIP-based electrochemical sensors is presented, followed by current issues and future development depicted at the last section of the Review.

While resistive pulse sensor (RPS) has been used to characterize the nano/micro-targets (cells, biomolecules, etc.) in biomedical research, one long standing drawback is its low throughput. Here we report a novel geometry modulation based RPS to improve the throughput without increasing the complexity of measurement electronics. The sensor consists of multiple parallel sensing channels whose geometries are uniquely designed based on 7-bit spreading sequences. Because of the unique geometry, when a particle passes a sensing channel, the voltage signal from this channel is encoded by a specific waveform. Only a DC source was applied, and only one combined signal from all sensing channels was collected. For demodulation, the maximum correlation coefficient between the combined signal and each template waveform was used to identify the passage of a particle from a specific sensing channel, and the occurring time of the passage. An iterative cancellation scheme was developed to extract the identified waveforms, by a series of subtractions of the identified waveforms with amplitudes from high to low, until the correlation coefficients between the remaining signal with all template waveforms became less than 0.4 (weak correlation). Mixtures of different-sized polystyrene particles were used to test the device. Results showed that the device is capable of accurately sizing and counting various microparticles with errors of 5.8% and 5.2% while the throughput was improved 300%. With the simple structure and measurement setup, the geometry-modulated RPS has great potential for the detection and analysis of a variety of micro/nano bio-objects.

1D nanostructures of TiO₂ have been extensively researched in chemical sensing. The need for deployment of 3D nanostructures such as flower-like and urchin-like morphology for chemical sensing is very essential. This morphology provides distinctive attributes because of the properties afforded by the micrometre and nanometre building blocks within the crystal of the nanomaterial. 3D nanostructure nanorutile titania was fabricated using a facile hydrothermal method. The gas sensing performance showed that the hierarchical morphology, high surface area, high porosity and humidity played a vital role in the sensing of ethanol vapour at room temperature. The radially aligned nanorutile (RANR) TiO₂ sensor showed high sensitivity with responses of 86.75% and 38.27% towards ethanol and methanol vapours, respectively. The sensor displayed good sensitivity, reproducibility, rapid response, and recovery times towards alcohol vapours.

Recently, significant efforts have been made to develop prostheses, soft rehabilitation, and assistive devices that enhance the quality of life of limb amputees and the activities of daily living (ADL) of stroke patients. Therefore, this present study provides a general overview of the current prosthetic, assistive, and rehabilitative devices with a focus on actuators that provide actuation via shape-memory alloys (SMA). Shape-memory alloy (SMA)-based actuators are the subject of considerable research as they possess high force-to-weight ratio, quiet operation, muscular mobility, bio-compatibility, and accessible design options, all of which can potentially be used to develop inventive actuating systems. Several studies have examined the use of SMA-actuated devices in the medical and engineering industry. They have also, more recently, been used to develop soft robotic systems. This present review primarily focuses on the characterization, number, type of actuator, degrees of freedom (DOF), weight, cooling technique, control strategies, and applications as well as the advantages and disadvantages of plate, spring, and wire-based SMA actuators. Composite-based upper limb SMA actuators were also reviewed and compared in terms of the matrix, reinforcing materials, SMA configuration actuator dimensions, and manufacturing method as well as their advantages and disadvantages. The findings indicate that, in the last few years, more studies have examined developing novel intelligent materials with which to improve hand flexibility. Therefore, SMA materials have a promising future in the development of intelligent designs for hand-robots. They may also be used to improve control robustness as well as the accuracy of hand functions for ADL and effective rehabilitation.

Diabetes is a serious disease with a huge number of patients worldwide. Glucose levels in people with diabetes are above 6.6 mM in blood samples and 200 μM in saliva samples. Metal-organic frameworks (MOFs) have outstanding properties for glucose sensors, such as a large surface area and being rich in active sites. In this research, a silver nanoparticle@Ni-BTC (AgNP@Ni-BTC) composite was synthesized through one-pot synthesis using a microwave at 130 °C for 1 hour at 200 W. The results showed that the 4%AgNP@Ni-BTC-modified carbon paste electrode obtained better sensor performance than Ni-BTC with a limit of detection (LoD) of 14.73 μM, a sensitivity of 6584.89 μA mM⁻¹ cm⁻², and a linear range of 10–1250 μM. The 4%AgNP@Ni-BTC-modified carbon paste electrode also had better stability than Ni-BTC and had good reproducibility. Glucose detection tests on salivary samples showed that the 4%AgNP@Ni-BTC-modified carbon paste electrode could be used to measure glucose levels in salivary samples.

The rapid and sensitive detection of pepsin plays an important role in clinical and medical practice. A label-free and sensitive micro-tapered long-period fiber grating (MTLPFG) sensor that functionalized by graphene oxide (GO) was proposed for pepsin detection. MTLPFG was fabricated with CO₂ laser heating and tapered to form a series of periods, and the GO that activated oxygen groups by EDC/NHS was deposited onto MTLPFG surface. On account of large specific surface area and oxygen containing groups of GO, the biomolecules can be adsorbed on the GO surface through amide groups and π-π stacking. The spectrum variation trend during sensing process obeys Langmuir absorption mode, which illustrates biomolecule adsorption on GO layer. The bare MTLPFG and GO-MTLPFG separately demonstrate the limit of detection (LOD) of 104.6 ng/ml and 25.79 ng/ml, which corresponding to the effectively detection range of 1–1000 ng/ml. Combination of GO and optical fibers exhibit great adaptive capacity to the biosensors, and provides inspirations for biochemical sensing applications.

The development of simple sensing platforms for evaluating the oral conditions has attracted great attentions for healthcare. Saliva or toothpaste contains various analytes that can indicate health conditions. A salivary glucose sensing platform can provide a convenient and non-invasive alternative detection approach for diabetic patients. Toothbrush is used every day, and it has an easy access to saliva biomarker and toothpaste residues. Here, we demonstrate for the first time an amperometric biosensor on a toothbrush, using glucose as a typical analyte. The carbon graphite ink and the Ag/AgCl ink are painted on a toothbrush as the sensing electrodes, followed by the enzyme immobilization. The sensor shows an excellent detection performance for glucose with a concentration ranging from 0.18 mM to 5.22 mM and a short detection time of less than 5 min. The sensor is promising for the non-invasive monitoring of salivary glucose levels in diabetic patients when they brush their teeth. We anticipate that these results would open up exciting opportunities for developing new toothbrush sensors, as well as advance related healthcare applications.

Developing efficient monitoring systems to control reinforced concrete structures (RCS) is still an open research line in the building sector. Thus, in this work was proposed the novelty use of Ni voltammetric sensor to control the concrete conditions by means of PCA model. The efficiency of voltammetric sensors are verified in other sectors like food or wastewater treatment, where the sensors are used in liquid media, in the study was intended verify the high potential use of this sensors in porous materials such as concrete. With this purpouse the sensor response was characterized in three different concretes (w/c = 0.6, w/c = 0.5 and w/c = 0.4) and three different concrete conditions (water satured conditions, presence of chlorides and concrete carbonation). Then, was developed a PCA model, where was verified the capability of the sensor to classify the concrete state. The validation of the model pointed an acceptance range between 78.3% and 95.4% (with a 95% confidence index).