Continuous production of bimetallic nanoparticles on carbon nanotubes based on 3D-printed microfluidics.

Nanoparticle-functionalized carbon nanotubes are promising in many research fields, especially in sensing, due to their intriguing performance in catalysis. However, these nanomaterials are mainly produced through batch processes under harsh conditions, thus encountering inherent limitations of low throughput and uncontrollable morphology of functional nanoparticles (NPs). In this work, we propose a method for high-yield and continuous production of bimetallic (Pt-Pd) NPs on multi-walled carbon nanotubes (MWCNTs) at room temperature through a custom 3D-printed microfluidic platform. A homogenous particle nucleation and growth environment could be created on the microfluidic platform that was equipped with two 3D-printed micromixers. Pt-Pd NPs loaded on MWCNTs were prepared in the microfluidic platform with high throughput and controlled size, dispersity and composition. The synthetic parameters for these nanocomposites were investigated to optimize their electrocatalytic performance. The optimized nanocomposites exhibited excellent electrocatalytic activity with exceptional sensitivity and wide detection range, superior to their counterparts prepared via conventional approaches. This method proposed here could be further adapted for manufacturing other catalyst support materials, opening more avenues for future large-scale production and catalytic investigation of functional nanomaterials.

Multiplexed detection of biomarkers using a microfluidic chip integrated with mass-producible micropillar array electrodes.

Quantifying multiple biomarkers with high sensitivity in tiny biological samples is essential to meet the growing demand for point-of-care testing. This paper reports the development of a novel microfluidic device integrated with mass-producible micropillar array electrodes (µAEs) for multiple biomarker detections. The µAE are mass-fabricated by soft lithography and hot embossing technique. Pt-Pd bimetallic nanoclusters (BNC) are modified on the surface of µAEs by constant potential (CP)/multi-potential step (MPS) electrodeposition strategies to improve the electroanalytical performance. The experimental result displays that Pt-Pd BNC/µAEs have good sensitivity enhancement compared with bare planar electrodes and bare µAEs, the enhancement being 56.5 and 9.5 times respectively, from the results of the H2O2 detection. Furthermore, glucose, uric acid and sarcosine were used as model biomarkers to show the biosensing capability with high sensitivity. The linear range and LOD of the glucose, uric acid and sarcosine detection are 0.1 mM-12 mM, 10 µM-800 µM and 2.5 µM-100 µM, 58.5, 3.4 and 0.4 µM, respectively. In particular, biosensing chips show wide linear ranges covering required detection ranges of glucose, uric acid and sarcosine in human serum, indicating the developed device has great potential in self-health management and clinical requirements.

Can Trust Bring Satisfaction to the Festival Under Pandemic?

In existing festival research, trust is often placed at the post-experience stage by scholars, and there is no research to explore the relationship between festivalscape, trust, and experience. In addition, the main function of trust is to reduce uncertainty and risk perception. Existing festival-related research scenarios do not have typical risks, which will limit the findings of the research. This research focuses on festivals under covid-19 pandemic, which is a typical risky scenario. Exploring the antecedent variables and the consequences of the trust of the festival participants in this context may therefore make up the deficiency of existing research. Several interesting findings have been made: the perception of the festivalscape during the pandemic has been significantly simplified. Epidemic prevention measures and staff may increase trust, but trust cannot have a direct and significant impact on festival satisfaction. While staff positively strengthen trust, they will have a significant negative impact on satisfaction.

Development of a novel microfluidic biosensing platform integrating micropillar array electrode and acoustic microstreaming techniques.

Quantifying biomarkers at the early stage of the disease is challenging due to the low abundance of biomarkers in the sample and the lack of sensitive techniques. This article reports the development of a novel microfluidic electrochemical biosensing platform to address this challenge. The electrochemical sensing is achieved by utilizing a micropillar array electrode (µAE) coated with 3D bimetallic Pt-Pd nanotrees to enhance the sensitivity. A bubble-based acoustic microstreaming technique is integrated with the device to increase the contact of analyte molecules with the surface of electrodes to further enhance the electrochemical performance. The current density of Pt-Pd NTs/µAE with acoustic microstreaming is nearly 22 times that of the bare planar electrode in potassium ferrocyanide solution. The developed biosensor has demonstrated excellent sensing performance. For hydrogen peroxide detection, both the Pt-Pd NTs/µAE and acoustic microstreaming contribute to the sensitivity enhancement. The current density of the Pt-Pd NTs/µAE is approximatively 28 times that of the bare µAE. With acoustic microstreaming, this enhancement is further increased by nearly 1.6 times. The platform has a linear detection range of 5-1000 µM with a LOD of 1.8 µM toward hydrogen peroxide detection, while for sarcosine detection, the linear range is between 5 and 100 µM and LOD is 2.2 µM, respectively. Furthermore, the sarcosine biosensing shows a high sensitivity of 667 µA mM-1∙cm-2. Such a sensing platform has the potential as a portable device for high sensitivity detection of biomarkers.

High-Throughput Microfluidic Production of Bimetallic Nanoparticles on MXene Nanosheets and Application in Hydrogen Peroxide Detection.

Nanoparticle-functionalized transition-metal carbides and nitrides (MXenes) have attracted extensive attention in electrochemical detection owing to their excellent catalytic performance. However, the mainstream synthetic routes rely on the batch method requiring strict experimental conditions, generally leading to low yield and poor size tunability of particles. Herein, we report a high-throughput and continuous microfluidic platform for preparing a functional MXene (Ti3C2Tx) with bimetallic nanoparticles (Pt-Pd NPs) at room temperature. Two 3D micromixers with helical elements were integrated into the microfluidic platform to enhance the secondary flow for promoting transport and reaction in the synthesis process. The rapid mixing and strong vortices in these 3D micromixers prevent aggregation of NPs in the synthesis process, enabling a homogeneous distribution of Pt-Pd NPs. In this study, Pt-Pd NPs loaded on the MXene nanosheets were synthesized under various hydrodynamic conditions of 1-15 mL min-1 with controlled sizes, densities, and compositions. The mean size of Pt-Pd NPs could be readily controlled within the range 2.4-9.3 nm with high production rates up to 13 mg min-1. In addition, synthetic and electrochemical parameters were separately optimized to improve the electrochemical performance of Ti3C2Tx/Pt-Pd. Finally, the optimized Ti3C2Tx/Pt-Pd was used for hydrogen peroxide (H2O2) detection and shows excellent electrocatalytic activity. The electrode modified with Ti3C2Tx/Pt-Pd here presents a wide detection range for H2O2 from 1 to 12 000 µM with a limit of detection down to 0.3 µM and a sensitivity up to 300 µA mM-1 cm-2, superior to those prepared in the traditional batch method. The proposed microfluidic approach could greatly enhance the electrochemical performance of Ti3C2Tx/Pt-Pd, and sheds new light on the large-scale production and catalytic application of the functional nanocomposites.

Numerical Study on a Bio-Inspired Micropillar Array Electrode in a Microfluidic Device.

The micropillar array electrode (µAE) has been widely applied in microchip-based electrochemical detection systems due to a large current response. However, it was found that amplifying the current through further adjusting geometrical parameters is generally hindered by the shielding effect. To solve this problem, a bio-inspired micropillar array electrode (bµAE) based on the microfluidic device has been proposed in this study. The inspiration is drawn from the structure of leatherback sea turtles' mouths. By deforming a µAE to rearrange the micropillars on bilateral sides of the microchannel, the contact area between micropillars and analytes increases, and thus the current is substantially improved. A numerical simulation was then used to characterize the electrochemical performance of bµAEs. The effects of geometrical and hydrodynamic parameters on the current of bµAEs were investigated. Moreover, a prototypical microchip integrated with bµAE was fabricated for detailed electrochemical measurement. The chronoamperometry measurements were conducted to verify the theoretical performance of bµAEs, and the results suggest that the experimental data are in good agreement with those of the simulation model. This work presents a novel bµAE with great potential for highly sensitive electrochemical detection and provides a new perspective on the efficient configuration of the µAE.

A Ti3 C2 TX /Pt-Pd based amperometric biosensor for sensitive cancer biomarker detection.

The detection of cancer biomarkers is of great significance for the early screening of cancer. Detecting the content of sarcosine in blood or urine has been considered to provide a basis for the diagnosis of prostate cancer. However, it still lacks simple, high-precision and wide-ranging sarcosine detection methods. In this work, a Ti3 C2 TX /Pt-Pd nanocomposite with high stability and excellent electrochemical performance has been synthesized by a facile one-step alcohol reduction and then used on a glassy carbon electrode (GCE) with sarcosine oxidase (SOx ) to form a sarcosine biosensor (GCE/Ti3 C2 TX /Pt-Pd/SOx ). The prominent electrocatalytic activity and biocompatibility of Ti3 C2 TX /Pt-Pd enable the SOx to be highly active and sensitive to sarcosine. Under the optimized conditions, the prepared biosensor has a wide linear detection range to sarcosine from 1 to 1000 µM with a low limit of detection of 0.16 µM (S/N = 3) and a sensitivity of 84.1 µA/mM cm2 . Besides, the reliable response in serum samples shows its potential in the early diagnosis of prostate cancer. More importantly, the successful construction and application of the amperometric biosensor based on Ti3 C2 TX /Pt-Pd will provide a meaningful reference for detecting other cancer biomarkers.

Electrochemical Performance of Micropillar Array Electrodes in Microflows.

The microchip-based electrochemical detection system (µEDS) has attracted plenty of research attention due to its merits including the capability in high-density integration, high sensitivity, fast analysis time, and reduced reagent consumption. The miniaturized working electrode is usually regarded as the core component of the µEDS, since its characteristic directly determines the performance of the whole system. Compared with the microelectrodes with conventional shapes such as the band, ring and disk, the three-dimensional (3D) micropillar array electrode (µAE) has demonstrated significant potential in improving the current response and decreasing the limits of detection due to its much larger reaction area. In this study, the numerical simulation method was used to investigate the performance of the µEDS, and both the geometrical and hydrodynamic parameters, including the micropillars shape, height, arrangement form and the flow rate of the reactant solution, were taken into consideration. The tail effect in µAEs was also quantitatively analyzed based on a pre-defined parameter of the current density ratio. In addition, a PDMS-based 3D µAE was fabricated and integrated into the microchannel for the electrochemical detection. The experiments of cyclic voltammetry (CV) and chronoamperometry (CA) were conducted, and a good agreement was found between the experimental and simulation results. This study would be instructive for the configuration and parameters design of the µEDS, and the presented method can be adopted to analyze and optimize the performance of nanochip-based electrochemical detection system (nEDS).

Development of micropillar array electrodes for highly sensitive detection of biomarkers.

Micropillar array electrodes (µAEs) have been widely applied in electrochemical detection owing to their advantages of increased mass transport, lower detection limit, and potential to be miniaturized. This paper reports the fabrication, simulation, surface modification, and characterization of PDMS-based µAEs coated with gold films. The µAEs consist of 9 × 10 micropillars with a height of either 100 µm, 300 µm, or 500 µm in a 0.09 cm2 region. Numerical simulation was employed to study the influence of geometrical parameters on the current density. The µAEs were fabricated by soft lithography and characterized using both SEM and cyclic voltammetry. Experiments revealed that high pillars enabled enhanced voltammetric current density regardless of the scan rates. The platinum-palladium/multi-walled carbon nanotubes (Pt-Pd/MWCNTs) were coated on the µAEs to improve their electrochemical detection capability. The µAEs demonstrated 1.5 times larger sensitivity compared with the planar electrode when hydrogen peroxide was detected. Furthermore, µAE500 with Pt-Pd/MWCNTs was employed to detect sarcosine, a potential biomarker for prostate cancer. The linear range and limit of detection for sarcosine were from 5 to 60 µM and 1.28 µM, respectively. This detection range covers the concentration of sarcosine in human tissues (0-60 µM). These results suggest that the µAEs have better detection performance in comparison to planar electrodes due to their large surface area and pillar height. This paper provides essential guidelines for the application of µAEs in high sensitivity electrochemical detection of low abundance analytes.

The Effect of Sensor Dimensions on the Performance of Flexible Hot Film Shear Stress Sensors.

This paper presents a study to determine the effect of sensor dimensions (length, width, and thickness) on the performance of flexible hot film shear stress sensors. The sensing component of a hot film sensor is nickel thermistor, and the flexible substrate material is polyimide. Several groups of flexible hot film shear stress sensors with different lengths, widths, and thicknesses were studied. The temperature coefficient of resistance (TCR) was measured. The TCR increased slightly with increasing thickness. The frequency response (time constant) of the flexible hot film shear stress sensor was obtained by the square wave, while the sensitivity was tested in a wind tunnel. The study found that as the sensor length was shortened, the frequency response increased, and the sensitivity decreased.