Array Surface Research Articles

Rapid fabrication of through-hole arrays in thin glass by femtosecond laser bursts assisted with chemical etching

A large-area vertical through-hole array in thin glass is rapidly fabricated by using femtosecond laser bursts assisted with chemical etching. By investigating the effects of the sub-pulse number and total pulse energy on the morphologies of the ablated microholes, as well as the effects of the chemical etching time and the concentration of HF acid solution on the morphologies of the through-holes, it is found that only under the condition that the upper surface of the glass microhole arrays is not ablated, but the exit is ablated by the femtosecond laser bursts with the increase of the sub-pulse number, a uniform and nearly vertical through-hole array can be obtained after etching in 5-wt% HF acid solution for 20 min. This single-step femtosecond laser bursts scanning method can significantly improve the fabrication efficiency of the ablated microhole arrays to about 18,000 microholes per second, which might provide a new technical guide for rapidly fabricating large-area vertical through-hole arrays in thin glass.

Optimization of Nanostructure and Characterization: Anodization of TiO2 in the Polyethylene Glycol-Based Electrolyte.

The homogeneity and stability of the structure of anodic TiO2 nanotube (ATNT) arrays have been a hot topic in materials synthesis research. In this work, the current density distribution during the anodization of ATNT arrays was optimized by adding polyethylene glycol-600 (PEG-600) to the conventional ethylene glycol-based electrolyte, which enhanced the dependence of the electronic current on the applied voltage, thus providing a stabilizing effect on anodization and improving the homogeneity of the pores on the surface of ATNT arrays. A new image processing approach, called the region-growing method, is reported in this work, which can quantitatively analyze the pore size of ATNT arrays through SEM images, and the surface morphology of ATNT arrays was evaluated based on this. The most stable anodization was obtained with a 50 wt % PEG-600 addition, and the equivalent diameters of the pores prepared at applied voltages of 40, 50, and 60 V were 34.5340, 42.4010, and 50.4791 nm, respectively, with a linear correlation of 0.9999.

Interfacial [S─Cu─C] Bonds Induced π-d Electron Coupling Toward Modulating Charge Transfer for Efficient Solar Water Oxidation.

Regulating the interfacial electric field to achieve rapid charge transfer is crucial for superior photoelectrochemical water splitting. Herein, the ultra-thin hydrogen-substituted graphdiyne (HsGDY) is precisely assembled on the surface of CdS nanorod array (Cu-CdS-HsGDY) by an in situ polymerization strategy. The strong π-d electron coupling is aroused by the delocalized π electrons of HsGDY and the delocalized d electrons of CdS through the interfacial [S─Cu─C] bonds. The strong interfacial electric field can effectively promote the charge localization distribution and reduce the charge transfer resistance. The optimized Cu-CdS-HsGDY photoanode obtain a photocurrent density as high as 4.83 mA cm-2 at 1.23 V versus reversible hydrogen electrode in neutral electrolyte solution under AM 1.5G illumination, which is 6.8 times that of the pristine CdS. Moreover, the photoanode maintains an initial photocurrent density of 84% within 4 h without any assistance of sacrificial agents, which is a rather competitive performance of similar sulfide photoanodes. The mechanism of strong π-d electron coupling on interfacial charge transfer and surface reaction kinetics is investigated by transient spectroscopy measurements, density functional theory calculation, and finite element simulation analysis. This work provides new insights into designing a reasonable interface structure to regulate charge transfer for achieve efficient PEC water splitting.

Exploring mechanisms of asymmetric droplet impact dynamics on roughness gradient surface

Droplet impact on surfaces with varying roughness and wettability is a common phenomenon in both natural and industrial environments. While previous studies have primarily examined asymmetric droplet rebound driven by impact velocity or Weber number, the influence of surface structure and associated impact mode transitions has received less attention. In this study, molecular dynamics simulations and detailed analyses are employed to investigate the mechanisms governing droplet rebound on nanopillar arrays with gradient distributions. Results reveal that nanopillar height significantly influences rebound direction, with two distinct directional transitions occurring as the height increases. Additionally, the effects of surface structure and Weber number on impact patterns, rebound velocity, and contact time are systematically evaluated, with contact angle calculations shedding light on the underlying force mechanisms. A phase diagram is developed to illustrate the relationship between rebound direction, Weber number, and nanopillar height. The study further extends the analysis to substrates with bidirectional gradient distributions, demonstrating consistency with single-directional gradient results and validating the broader applicability of the findings. This research provides critical insights into droplet dynamics on roughness gradient surfaces, emphasizing the role of nanopillar height and impact mode in controlling droplet behavior and highlighting potential applications in the design of structured array surfaces.

A Clinically Feasible Electrode Array for 3D Intraoperative Electrical Impedance Tomography-Based Surgical Margin Assessment in Robot-Assisted Radical Prostatectomy.

A novel small form factor circular electrode array was designed specifically for electrical impedance tomography (EIT) based assessment of surgical margins during robot assisted radical prostatectomy (RARP). The electrode array consists of 33 gold-plated electrodes arranged within a 9.5 mm diameter circular footprint on the end of a surgical probe that can be introduced through a standard 12 mm laparoscopic port used during RARP. The electrode array contains 8 larger, low-contact impedance outer electrodes dedicated for current drive and an internal grid of 25 smaller electrodes for simultaneous voltage measurement. Separating electrode geometry by function is designed to improve current delivery, speed, and resolution while reducing hardware requirements. Simulations demonstrated that 1 mm diameter hemispherical prostate cancer inclusions could be localized within regions of adipose and benign prostate tissue; 1.5 mm diameter inclusions were required for localization within muscle tissue. A 2.38 mm diameter aluminum rod in 0.2 S/m saline could be localized throughout the imaging domain with a position error of less than 2.5 mm for depths from the electrode array surface of up to 1.7 mm. Ex vivo tissue experiments with a bovine model demonstrate visual congruence of muscle and adipose tissue locations between the sample and reconstructed images. Simulation and experimental results indicate good detection and location of inclusions. These results suggest the proposed electrode array design can provide sufficient accuracy in the detection and localization of prostate cancer against clinically relevant background tissues for use during RARP.

A hybrid solar and RF energy harvester for applications of self-Powered wireless sensor nodes

A hybrid solar and RF energy harvester is proposed for applications in self-powered wireless sensor nodes. A planar slot antenna array backed by substrate integrated waveguide (SIW) cavity is produced for RF energy harvesting. A designed rectifier connected to the antenna array converts the received RF energy into DC energy. Solar cells are placed on the rest of the antenna array except slots, fully utilizing the array's surface. The solar cell coverage ratio reaches 87%. The measurement results indicate that under solar simulator illumination, the solar energy harvester has a short-circuit current of 15.7 A, an open-circuit voltage of 0.542 V, and a maximum output power of 5.81 W. Under the RF power density of 85.5 μW/cm2, the RF energy harvester reaches its peak power conversion efficiency (PCE) of 69%. All simulated and measured results are in good agreement, verifying the capabilities of the designed hybrid harvester.

Radiofrequency Enhancer to Recover Signal Dropouts in 7 Tesla Diffusion MRI.

Diffusion magnetic resonance imaging (dMRI) allows for a non-invasive visualization and quantitative assessment of white matter architecture in the brain by characterizing restrictions on the random motion of water molecules. Ultra-high field MRI scanners, such as those operating at 7 Tesla (7T) or higher, can boost the signal-to-noise ratio (SNR) to improve dMRI compared with what is attainable at conventional field strengths such as 3T or 1.5T. However, wavelength effects at 7T cause reduced transmit magnetic field efficiency in the human brain, mainly in the posterior fossa, manifesting as signal dropouts in this region. Recently, we reported a simple approach of using a wireless radiofrequency (RF) surface array to improve transmit efficiency and signal sensitivity at 7T. In this study, we demonstrate the feasibility and effectiveness of the RF enhancer in improving in vivo dMRI at 7T. The electromagnetic simulation results demonstrated a 2.1-fold increase in transmit efficiency with the use of the RF enhancer. The experimental results similarly showed a 1.9-fold improvement in transmit efficiency and a 1.4-fold increase in normalized SNR. These improvements effectively mitigated signal dropouts in regions with inherently lower SNR, such as the cerebellum, resulting in a better depiction of principal fiber orientations and an enhanced visualization of extended tracts.

Stable Droplet Manipulation in Multiple Directions on a Magnetically Responsive Micropillar Array Surface

AbstractDroplets constitute an essential discrete form of liquids and are prevalent in both natural and industrial fields. Droplet manipulation technologies have broad application prospects in various fields, including biomedical devices, chemical engineering, water collection, and so on. The manipulation of surfaces with magnetic responsiveness has emerged as a pivotal technique in droplet control owing to its flexibility and precision in remote operations. In this study, the dynamic rolling behavior of low‐surface‐tension working fluids and water droplets on a superhydrophobic magnetically responsive micropillar array (SMMA) is investigated, with a focus on the mechanisms that generate instabilities during the directional rolling motion of droplets. The factors influencing these instabilities are studied using data analysis. Moreover, techniques for capturing and releasing droplets are investigated, offering significant insights into the efficient handling of minute amounts of liquids in experiments and the automation of intricate chemical processes.

Free Electron Density Gradients Enhanced Biosensor for Ultrasensitive and Accurate Affinity Assessment of the Immunotherapy Drugs.

Accurate affinity assessments play an important role in drug discovery, screening, and efficacy evaluation. Label-free affinity biosensors are recognized as a dependable and standard technology for addressing this challenge. This study constructs a free electron density gradient-enhanced meta-surface plasmon resonance (FED-MSPR) biosensor through a finite-difference time-domain simulation model, the biosensor demonstrates superior detection performance in accurately determining affinity and kinetic rate constants. By controlling the dielectric properties of the metal on the surface of the nanocup arrays, the plasmon resonance effects are easily tuned without changing the nanostructure design. Compared with the single-layer gold chip, the triple-layer FED-MSPR chip demonstrated a four-fold improvement in resolution at the optimal resonance peak. Additionally, the sensitivity and figure of merit (FOM) of the multi-layer chip increased by 3.5 and 7.99 times, respectively. Following modification with high- and low-staggered carboxylation, the noise-signal ratio and baseline stability of the real-time kinetic curves based on these chips are significantly enhanced. The developed carboxylation FED-MSPR platform is successfully used to perform affinity assays for Adalimumab and TNF-α protein, resulting in favorable dynamic curves. These findings validate the proposed FED-MSPR biosensor platform as cost-effective, rapid, sensitive, and label-free, facilitating real-time quality control in drug development.

Photonic Microbead Array Digital Time-Resolved Fluorescence Ultrasensitive Platform for Simultaneous Detection of Multiple Mycotoxins.

Limitations in the sensitivity, linear detection range, and cross-reaction of lateral flow immunoassays mainly hamper their application in rapid screening for multiple targets. In this work, we designed a new time-resolved fluorescence immunoassay (TRFIA) platform to overcome these limitations. This platform uses europium chelate polystyrene (PS@Eu) nanoparticles conjugated with monoclonal antibodies to sense multiple mycotoxins. We employed a competitive TRFIA protocol in which the conjugated PS@Eu was used on the surfaces of photonic microbead arrays (PMAs). The TRFIA signal of PMAs on the pad was recorded with the digital time-resolved fluorescence reader. The developed TRFIA shows wide detection linear ranges (0.01-1000 ng/mL for DON, 0.1-100 ng/mL for OTA, and 0.01-100 ng/mL for AFB1), low limits of detection (LODs) (7.9 pg/mL for DON, 18 pg/mL for OTA, and 7.7 pg/mL for AFB1), good specificity, good recovery ratios (76.68-117.26%), and good reproducibility in grain samples. The simulated fluorescence enhancement effect of PMA indicated that the electric field distribution on the surface of PS@Eu on PMA is twice higher than that on the surface of PS@Eu. The new TRFIA for three kinds of mycotoxins was 1000-fold more sensitive than the classical TRFIA, and it has great potential application in rapid screening for multiple targets.

Growth mechanism and SERS effect of Ag nanowire arrays prepared by solid-state ionics method

Solid-state ionic method has attracted more and more attention due to its simple operation and controllable preparation, but its growth mechanism is still uncertain. In this work, Ag nanowire (Ag NW) arrays prepared by solid-state ionics method at 5 μA impressed currents using fast ionic conductor RbAg4I5 films and different metal electrodes were reported. The conduction mode of Ag+ in RbAg4I5 films, the growth mechanism of Ag NW arrays prepared by solid-state ionics method and the effect of microscopic morphology on surface-enhance Raman scattering (SERS) performance were investigated. The results show that Ag nanoparticles (Ag NPs) with diameters from 40 nm to 70 nm were attached to the surface of Ag NW arrays with diameters of 80–150 nm prepared with different metal electrodes, which lead to Ag NW arrays have high surface roughness. The conduction velocity and stability of Ag+ in RbAg4I5 films are closely related to the morphology of Ag NW arrays. The irregular electrode interface and apical growth advantage resulted in the fractal dimension of Ag NW arrays prepared with Ag electrodes is 1.69 due to macroscopic dendritic structure. Ag NW arrays have excellent SERS performance due to the many Ag NPs attached to the surface of the closely aligned Ag NWs, the limit of detection (LOD) for Basic Fuchsin (BF) and Crystal Violet (CV) detected by Ag NW arrays SERS substrates prepared with Ag electrodes are as low as 10−11and 10−14mol/L, respectively. This paper provides a reference for the preparation method of metal nanostructures, Ag NW arrays have good potential for application in the field of trace analysis.

Investigation of Energy Deposition by Soft X-rays into Solar Cell Materials

A high-altitude nuclear detonation releases a significant portion of energy as X-rays with a blackbody spectrum. Satellites are particularly vulnerable to prompt soft X-rays (~1 keV) absorbed within a few microns of the surface of the solar array, causing melting and evaporation of its materials. The absorption of soft X-rays in solar cell materials is studied using GEANT4 computer software. Energy deposition as a function of depth (depth-dose profile) is calculated for slab geometries of dielectric and metallic materials. The photo-absorption and Compton scattering of X-rays and the contribution of secondary radiation, such as photo-electrons, Auger-electrons, and fluorescence photons are taken into account. The effect of the production of secondary radiation on the distribution of deposited dose in the near-surface region of materials is investigated. The results presented in this work are validated against published data and provide valuable insights into X-ray absorption by solar cell materials, the redistribution of energy by secondary radiation, and the spatial scale of power density deposition that can be used as a source term for the further thermomechanical analysis of a material’s phase transformations and melting.

Directional Transportation Behavior of Droplets on a Magnetically Responsive Micropillar Array Surface.

Technologies for manipulating droplets have applications in various fields, such as biomedical devices, chemical engineering, water collection, and thermal management. The morphology of magnetically responsive surfaces are modified using magnetic fields for inducing droplet directional rolling and bouncing. Herein, a study on the directional transport of droplets on magnetically responsive surfaces is reported, identifying three movement modes and analyzing the mechanisms influencing the transport behavior. The study explored working fluids with surface tension lower than that of water, achieving the directional transport of 30% ethanol droplets with a maximum transport velocity of 130 mm s-1. The practical applications of the droplets on a modified surface were analyzed, and methods were developed to accelerate droplet mixing. This study explored efficient operations and automation of complex chemical processes.

Enhanced speed of microswimmers adjacent to a rough surface.

Increased speed is not only the goal of human sports but also the aim we seek to achieve for artificial microswimmers. Microswimmers driven by various power mechanisms have shown unrivaled advantages in drug delivery and cancer therapy. Attaining high mobility with limited power has been a never-ending motive for researchers. We show the speed of squirmer-type microswimmers can be noticeably enhanced as they are released to move along the surface of a pillar array, which is constructed of multiple pillars of equal sizes and spacing. An additional pressure force arising from the significant low pressure between the swimmers and the surface is likely behind this enhancement. According to their polarity strengths, the speed of the microswimmers can be double or triple (or even more) compared with that in an unbounded environment. In particular, for systems requiring microswimmers moving along a complex path, the transport rate, instead of being slowed down, may be increased owing to the curvatures of the path constructed by the pillar arrays. We reveal two types of motion for microswimmers after increasing the pillar gap: free and forced oscillating. Our study sheds light on the hydrodynamic interactions between squirmer-type microswimmers and a rough wall.

Pinning of domain walls in epitaxial garnet film patterned by surface arrays of ferromagnetic metal particles

Rare-earth iron garnet epitaxial films famous for their unique magnetic, microwave and optical properties consistently attract high interest. Domain structure of both bulk and interfaces of garnet films is closely connected with their magnetic properties and magnetization dynamics. In this work, we investigate the magnetic behaviour and domain structure of an epitaxial bismuth-substituted lutetium iron garnet film with a regular array of planar submicron particles made of Co film or Co/Pt multilayer on its surface. Optical polarization microscopy and magnetic force microscopy techniques used for the characterization of these composite structures confirm the mutual influence of the garnet and metal nanostructured layers on each other. On the one hand, dense ordered metal particles provide the pinning of the surface magnetic domains of the garnet film, which further affects the organization of the bulk stripe domains. On the other hand, we observed that the domain structure in the metallic pattern is governed by the domain structure of the garnet placed beneath it.

Study on plasma expansion model of primary discharge on spacecraft solar array

In the space plasma environment, primary discharge may occur on the solar array and evolve into a destructive sustained arc, which threatens the safe operation of the spacecraft. Based on the plasma expansion fluid theory, a new multicomponent plasma expansion model is proposed in this study, which takes into account the effects of ion species, ion number, initial discharge current, and Low Earth Orbit (LEO) plasma environment. The expansion simulation of single-component and multicomponent ions is carried out respectively, and the variations of plasma number density, expansion distance, and speed during the expansion process are obtained. Compared with the experimental results, the evolution of propagation distance and speed is closed and the error is within a reasonable range, which verifies the validity and rationality of the model. The propagation characteristics of the primary discharge on the solar array surface and the influence of the initial value on the maximum propagation distance and the propagation current peaks are investigated. This study can provide important theoretical support for the propagation and evolution of the primary discharge and the key behavior of the transition to secondary discharge on spacecraft solar array.

Surface-enhanced Raman scatting microfluidic chip based on the identification competition strategy were used for rapid and simultaneous detection of liver cancer related proteins

Biomarker testing plays a crucial role in the early detection of liver cancer. Herein, we developed a dual-signal amplification approach utilizing magnetic aggregation and a recognition competition strategy for the simultaneous detection of alpha-fetoprotein (AFP) and manganese superoxide dismutase (MnSOD) in serum. 4-MBA@AuNPs@H1 and DTNB@AuNPs@H2 were synthesized by functionalizing Raman signaling molecules and aptamer complementary chains onto the surface of gold nanoparticles (AuNPs). The detection complex Raman signal molecule@AuNPs@H-Fe3O4@cDNA was assembled by conjugating 4-MBA@AuNPs@H1 and DTNB@AuNPs@H2 with two nucleic acid aptamers (cDNA1 and cDNA2) modified with Fe3O4 through partial base complementary pairing. The target protein exhibited specific binding with the aptamer, leading to the competitive displacement of 4-MBA@AuNPs@H1 and DTNB@AuNPs@H2 from the Fe3O4 array surface, consequently resulting in a reduction of the Surface-Enhanced Raman Spectroscopy (SERS) signal. Through this approach, the limit of detection (LOD) for AFP and MnSOD in serum was achieved at remarkably low levels of 5.89 pg/mL and 6.23 pg/mL, respectively, with a reaction incubation period of only 5 min. Finally, the platform was utilized for the quantification of AFP and MnSOD in the serum of a nude mouse hepatocellular carcinoma model. The results obtained through SERS were consistent with those from enzyme-linked immunosorbent assay (ELISA), validating its accuracy. This methodology presents a novel approach for the swift and concurrent detection of proteins, holding significant clinical promise for the early diagnosis of hepatocellular carcinoma.

Covalent Grafting of Tanfloc on Titania Nanotube Arrays: An Approach to Mitigate Bacterial Adhesion and Improve the Antibacterial Efficacy of Titanium Implants

AbstractImplanted medical devices often face the challenge of infections, which can compromise their successful integration and use. To address this issue, this study demonstrates the covalent grafting of a tannin‐based antimicrobial biopolymer tanfloc (TAN) onto the titania nanotube arrays (TiNTs) surface to enhance antibacterial properties. Due to its polyphenolic and ionic structural configuration, tanfloc possesses unique properties that enable it to interact with and disrupt bacterial cell walls and membranes. Combining the topographical effect of TiNTs with the inherent antibacterial properties of tanfloc, this approach aims to mitigate bacterial threats on medical implants effectively. The successful attachment of tanfloc on TiNTs is confirmed through X‐ray photoelectron spectroscopy (XPS) and Fourier‐transform infrared spectroscopy (FT‐IR). The antibacterial and antibiofilm efficacy of the tanfloc‐functionalized TiNTs is evaluated against Staphylococcus aureus (Gram‐positive) and Pseudomonas aeruginosa (Gram‐negative) bacteria. The findings suggest that the covalent conjugation of tanfloc onto TiNTs is a promising approach to improve the infection resistance of titanium‐based medical implants, with potential applications in orthopedic, dental, and other biomedical device areas.

Electrical resistivity imaging of crude oil contaminant in coastal soils – A laboratory sandbox study

Characterizing the subsurface distribution of crude oil after a spill in a coastal environment is challenging due to variations in the soil and fluid properties. In situ sampling is limited in capturing the lateral and vertical migration of the crude oil within the vadose and saturated zones. This study presents a laboratory sandbox framework used to assess the effectiveness of electrical resistivity imaging for investigating the spatiotemporal distribution of crude oil in coastal sandy soils. A sandbox with dimensions L = 240 cm, W = 60 cm, and H = 60 cm was constructed using a 10 mm plexiglass and filled to a 40 cm height with 2 mm medium to fine-grained sand. At each stage of the experiment, 20 kg of sand was mixed with 1 l of water to create moist sand, after which the mixture was flushed over 12 h to remove suspended fine particles. Both saturated and unsaturated conditions were simulated by setting the water table at 10 cm and draining a fully saturated system overnight. Two liters of crude oil were spilled and monitored for 30 h. A surface array of 98 electrodes, with a unit electrode spacing of 2 cm, was installed along two transects 12 cm apart. Resistivity measurements were collected using a dipole-dipole array before, during, and after the simulated crude oil spill. The time-lapse electrical resistivity results revealed an initial gravity-induced vertical migration under both saturated and unsaturated conditions; over time, lateral migration of crude oil became apparent. In the saturated zone, there was a noticeable reduction in the percentage difference in resistivity from 700 % to 400 % after 24 h, depicting a spatial and temporal redistribution of the crude oil attributed to variation in pore geometry. This highlights the sensitivity of electrical resistivity measurements to subtle but measurable anisotropy in the distribution of soil pores. Overall, electrical resistivity proved successful in imaging the non-ideal behavior of crude oil pollutants and the associated spatial changes in the pore-size distribution of subsurface sediments.

Study of ash deposition characteristics of photovoltaic arrays taking into account the effect of photovoltaic module spacing and its effect on output characteristics: Indoor experiment

The problem of ash deposition on the surface of photovoltaic (PV) arrays during actual operation seriously affects their power generation efficiency. Because traditional research does not consider the PV module spacing, it cannot reflect the actual PV array ash deposition problem. This study explored the influence of PV module spacing, combined with different tilt angles and inlet wind speeds, on the characteristics of ash deposition and power output of the PV array through indoor experiments. The study designed a set of experimental equipment for simulating the formation process of ash deposition on the surface of PV arrays and set up an experimental platform to measure the influence of ash deposition on the maximum output power (Pmax), open-circuit voltage (Uoc), and short-circuit current (Isc) of the PV modules. The findings indicate that as the tilt angle increases, the PV array experiences reduced ash deposition and increased output power. Conversely, higher inlet wind speeds lead to greater ash deposition and decreased output power. Moreover, widening the spacing between PV modules results in increased ash deposition and reduced output power. Notably, within the PV array, the front PV module accumulates more ash than the rear module, with larger particle sizes. These research findings have significant implications for optimizing PV array design and enhancing power generation efficiency.