One-step Fabrication Process Research Articles

Hollow fiber membranes with hierarchical spherulite surface structure developed by thermally induced phase separation using triple-orifice spinneret for membrane distillation

Polyvinylidene fluoride (PVDF) hollow fiber membranes were developed by the thermally induced phase separation (TIPS) process using a triple-orifice spinneret with solvent co-extrusion at the outermost channel for applications in membrane distillation (MD). The polymer surface concentration during membrane preparation was controlled by exploiting the interfacial interactions of the diluent and polymer at the extruded solvent surface. The membrane surface was controlled from a dense to a porous structure with a large pore size and a high porosity, which considerably enhanced the membrane water vapor permeability to 13.5 L m−2 h−1. Furthermore, the solvent co-extrusion was responsible for the formation of surface spherulites with different shapes, such as contacted spherulites, isolated spherulites, and isolated spherulites with humps. The spherulites with humps constructed a novel hierarchical structure, which created a superhydrophobic surface that conferred upon the PVDF membrane a remarkable wetting resistance in the MD process toward low-surface-tension saline water. More significantly, all the unique structures were achieved using the one-step membrane fabrication process of solvent co-extrusion without additional processes and materials. Thus, this work provides a new, simple, and useful alternative for the preparation of hollow fiber membranes with high performances for MD desalination.

Laser-Induced Flexible Electronics (LIFE) for Resistive, Capacitive and Electrochemical Sensing Applications

Engineering a cost-effective, flexible electronic device in a one-step fabrication process is quite challenging to perform. Herein, we have introduced a simple, low-cost, solid-state process for producing and printing of complex circuits using Laser-Induced Graphene (LIG). In the present work, LIG has been effectively and selectively formed from direct CO2 laser ablation on a polyimide sheet. Varying CO2 laser power and speed, the electrical conductivity of the LIG has shown a linear increment in the conductivity measurement. The laser-induced samples were structurally characterized using Scanning Electron Microscopy (SEM), EDX, X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy. The results show a one-step method to create Graphene-derived structures on the polyimide sheet surface. This method of generating LIG on a flexible substrate (polyimide sheet) offers an easy way to fabricate Laser-Induced Flexible electronics (LIFE) circuits. Using this, the feasibility and the realization of a capacitive touch sensor and liquid level sensor has been successfully demonstrated. Further, as a prototype system, the LIG was examined for the H2O2 electrochemical sensing application. It gives an appreciable response for the detection of H2O2 in comparison to other carbon-based electrodes with limit-of-detection (LOD) as $0.3~\mu \text{M}$ in a linear range from $1~\mu \text{M}$ to 10 $\mu \text{M}$ .

A one-step polymer screen-printing method for fabrication of microfluidic cloth-based analytical devices

We report the first use of a one-step polymer screen-printing method for fabrication of microfluidic cloth-based analytical devices (µCADs). The method involves a simple, low-cost and one-step fabrication process and requires only polystyrene and a patterned screen. Firstly, polystyrene solution is poured through the patterned screen and allowed to penetrate through the cotton fabrics to create a three-dimensional hydrophobic barrier which defined the test zones. Different types of cotton fabric and polystyrene concentrations were first investigated. By adjusting polystyrene concentration, various types of cotton cloth can be successfully fabricated. Under optimal condition, the smallest hydrophilic channel and hydrophobic barrier that the fabrication method can provide were 678 ± 59 µm and 329 ± 27 µm, respectively. High device-to-device repeatability was achieved with a relative standard deviation (%RSD) in the range of 1.10–2.03% (n = 64) obtained from the measured diameter of the circular-shaped fabricated test zones with a designed diameter of 5 and 7 mm. The cloth treatments using hot water, Na2CO3 and NaOH solutions were found to affect the wicking ability of the cloths where the highest wicking rate was found in the Na2CO3 treated-cloth followed by NaOH, hot water treated-cloths and untreated-cloth. To demonstrate the significance of the fabricated µCAD, the analysis of glucose and albumin in control human serum was carried out. The results showed no significant difference at 95% confident intervals of the glucose and albumin levels obtained from the µCAD analysis and the certified values verifying that the polymer-screen printing method can be alternatively used as a method for µCAD fabrication.

Continuous microfluidic encapsulation of single mesenchymal stem cells using alginate microgels as injectable fillers for bone regeneration

The encapsulation of cells in microscale hydrogels can provide a mimic of a three-dimensional (3D) microenvironment to support cell viability and functions and to protect cells from the environmental stress, which have been widely used in tissue regeneration and cell therapies. Here, a microfluidics-based approach is developed for continuous encapsulation of mesenchymal stem cells (MSCs) at the single-cell level using alginate microgels. This microfluidic technique integrated on-chip encapsulation, gelation, and de-emulsification into a one-step fabrication process, which enables scalable cell encapsulation while retaining the viability and functionality of loaded cells. Remarkably, we observed MSCs encapsulated in Ca-alginate microgels at the single-cell level showed significantly enhanced osteogenesis and accelerated mineralization of the microgels which occurred only after 7 days of induction. Furthermore, MSCs laden in alginate microgels displayed significantly enhanced bone formation compared to MSCs mixed with microgels and acellular microgels in a rat tibial ablation model. To conclude, the current microfluidic technique represents a significant step toward continuous single cell encapsulation, fabrication, and purification. These microgels can boost bone regeneration by providing a controlled osteogenic microenvironment for encapsulated MSCs and facilitate stem cell therapy in the treatment of bone defects in a minimally invasive delivery way. Statement of SignificanceThe biological functions and therapeutic activities of single cells laden in microgels for tissue engineering remains less investigated. Here, we reported a microfluidic-based method for continuous encapsulation of single MSCs with high viability and functionality by integrating on-chip encapsulation, gelation, and de-emulsification into a one-step fabrication process. More importantly, MSCs encapsulated in alginate microgels at the single-cell level showed significantly enhanced osteogenesis, remarkably accelerated mineralization in vitro and bone formation capacity in vivo. Therefore, this single-cell encapsulation technique can facilitate stem cell therapy for bone regeneration and be potentially used in a variety of tissue engineering applications.

Stimuli-Responsive Actuator Fabricated by Dynamic Asymmetric Femtosecond Bessel Beam for In Situ Particle and Cell Manipulation.

Microscale intelligent actuators capable of sensitive and accurate manipulation under external stimuli hold great promise in various fields including precision sensors and biomedical devices. Current microactuators, however, are often limited to a multiple-step fabrication process and multimaterials. Here, a pH-triggered soft microactuator (<100 μm) with simple structure, one-step fabrication process, and single material is proposed, which is composed of deformable hydrogel microstructures fabricated by an asymmetric femtosecond Bessel beam. To further explore the swelling-shrinking mechanism, the hydrogel porosity difference between expansion and contraction states is investigated. In addition, by introducing the dynamic holographic processing and splicing processing method, more complex responsive microstructures (S-shaped, C-shaped, and tortile chiral structures) are rapidly fabricated, which exhibit tremendous expected deformation characteristics. Finally, as a proof of concept, a pH-responsive microgripper is fabricated for in situ capturing polystyrene (PS) particles and neural stem cells rapidly. This flexible, designable, and one-step approach manufacturing of intelligent actuator provides a versatile platform for micro-objects manipulation and drug delivery.

Effect of MWCNT on the Structure and Property of Nanofibrous Bundles by Blown Bubble Spinning.

Many spinning patents and technologies have been explored to produce diverse types of nanomaterials for different applications. As a novel method, the blown bubble-spinning is a one-step process for fabrication of nanofibrous bundles. In this study, polyamide6/66(PA6/66) nanofibrous bundles filled with different concentrations of multi-walled carbon nanotubes (MWCNTs) were prepared by the blown bubble-spinning. The dispersion of MWCNT in nanofibers under different treatments was investigated and a detailed characterization focusing on the influence of the presence of MWCNT on the morphology, thermal property and electrical property was carried out. The results showed that MWCNTs treated by Tween60 and ultrasonication were embedded in the PA6/66 nanofibers with uniform dispersion. In addition, it was observed that thermal stability and electrical conductivity of nanofibrous bundles increased with an increase in MWCNT content. The PA6/66/MWCNT nanofibrous bundles fabricated by the blown bubble spinning have the great potential applications in sensors and supercapacitors.

A rapid one-step nanosecond laser process for fabrication of super-hydrophilic aluminum surface

This paper reports a way of forming super-hydrophilic surface on the pure aluminum plate (99.999% aluminum) that the nanoarray structure is formed on the surface using a nanosecond pulsed laser. It is found that different micro/nano structure have certain influence on the hydrophilicity of aluminum plates. Two different laser scanning methods, single horizontal and grid pattern scanning, were selected in this study. It was found that the scanning marking method of the grid pattern can form a relatively regular dot sequence nanoarray structure on the surface of aluminum plate. This structure makes the aluminum surface super hydrophilic with a contact angle of almost 0°.

Fully printed one-step biosensing device using graphene/AuNPs composite

Driven by the growing need of simple, cost efficient and flexible sensing systems, we have designed here a fully printed Reduced Graphene Oxide (rGO) based impedimetric sensor for one step sensing of DNA. The DNA sensor was fabricated by stamping of layered rGO and rGO/gold nanoparticles/single stranded DNA (rGO/AuNPs/ssDNA) composites over PET substrates using wax-printing technique. rGO works as an excellent working electrode, while the AuNPs create a suitable environment for ssDNA immobilization. Counter and reference electrodes were previously screen-printed on the plastic substrate, making thus a compact and highly integrated sensing platform. The change in electron transfer resistance after hybridization with a target ssDNA specific of Coxsackie B3 virus was monitored using electrochemical impedance spectroscopy (EIS), finding a linear response in the range of concentrations 0.01–20 µM. The novel, simple and straightforward one-step printing process for fabrication of a biosensing device developed keeps in mind the growing need of large scale device manufacturing. The successful proof-of-concept for the detection of DNA hybridization can be extended to other affinity biosensors, taking advantage of the integration of the bioreceptor on the sensor surface. Such ready-to-use biosensor would lead to a one-step electrochemical detection.

Transition States of Nanocrystal Thin Films during Ligand-Exchange Processes for Potential Applications in Wearable Sensors

Ligand exchange is an advanced technique for tuning the various properties of nanocrystal (NC) thin films, widely used in the NC thin-film device applications. Understanding how the NC thin films transform into functional thin-film devices upon ligand exchange is essential. Here, we investigated the process of structural transformation and accompanying property changes in the NC thin films, by monitoring the various characteristics of silver (Ag) NC thin films at each stage of the ligand-exchange process. A transition state was identified in which the ligands are partially exchanged, where the NC thin films showed unexpected electromechanical features with high gauge factors up to 300. A model system was established to explain the origin of the high gauge factors, supported by the observation of spontaneously formed nanocracks and metal-insulator transition from the structural analysis and charge transport study, respectively. Taking advantages of the unique electromechanical properties of the NC thin films, we fabricated flexible strain gauge sensor devices with high sensitivity, reliability, and stability. We introduce a one-step fabrication process, namely, "the time- and spatial-selective ligand-exchange process", for the design of low-cost and high-performance wearable sensors that effectively detect human motion, such as finger or neck muscle movement. This study provides a fundamental understanding of the ligand-exchange process in NCs, as well as an insight into the functionalities of the NC thin films for technological applications.

Direct Li+ incorporation during the anodic formation of compact TiO2 layers.

In this work, compact titanium oxide layers are formed by anodization in 1 M H3PO4 aqueous electrolyte containing LiClO4. Elastic Recoil Detection Analysis (ERDA) measurements demonstrate that incorporation of lithium ions occurs during anodization, and cell-voltage transient measurements evidence the different electronic properties of Li-doped TiO2 layers. The mechanism of direct incorporation of Li during the fabrication of TiO2 layers is discussed.

Synthesis of different types of carbon nanohybrid and their effects in polymer composites

Different types of carbon nanohybrid, including carbon nanotubes–graphene (CNT–G), carbon nanospheres–graphene (CNS–G), and carbon nanotubes–carbon nanospheres (CNT–CNS), were synthesized in a one-step fabrication process by chemical vapor deposition with acetylene as carbon source at different reaction temperatures and bimetallic catalyst (Ni/Cu) molar ratios, then applied as reinforcing nanofillers in polypropylene matrix to evaluate their effects on the resulting polymer composites. Characterization of the produced nanohybrids, including their size, structure, morphology, graphitization, composition, and surface area, was performed by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, electron-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller (BET) surface area measurements, respectively. The influence of the different nanofillers on the nanocomposites was analyzed by Raman spectroscopy, thermogravimetric analysis, and tensile testing. Finally, a mathematical model for the mechanical properties of the nanohybrids was applied, showing good agreement with experimental results.

Distributed Feedback Laser Based on Single Crystal Perovskite

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry–Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

Spontaneously formed high-performance charge-transport layers of organic single-crystal semiconductors on precisely synthesized insulating polymers

Charge-transporting semiconductor layers with high carrier mobility and low trap-density, desired for high-performance organic transistors, are spontaneously formed as a result of thermodynamic phase separation from a blend of π-conjugated small molecules and precisely synthesized insulating polymers dissolved in an aromatic solvent. A crystal film grows continuously to the size of centimeters, with the critical conditions of temperature, concentrations, and atmosphere. It turns out that the molecular weight of the insulating polymers plays an essential role in stable film growth and interfacial homogeneity at the phase separation boundary. Fabricating the transistor devices directly at the semiconductor-insulator boundaries, we demonstrate that the mixture of 3,11-didecyldinaphtho[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene and poly(methyl methacrylate) with the optimized weight-average molecular weight shows excellent device performances. The spontaneous phase separation with a one-step fabrication process leads to a high mobility up to 10 cm2 V−1 s−1 and a low subthreshold swing of 0.25 V dec−1 even without any surface treatment such as self-assembled monolayer modifications on oxide gate insulators.

High efficiency planar Sn–Pb binary perovskite solar cells: controlled growth of large grains via a one-step solution fabrication process

A well-controlled one-step method, assisted by sec-butyl alcohol solvent engineering and N,N-dimethylformamide solvent annealing under an N2 atmosphere, is developed for the growth of a high quality CH3NH3Pb(1−x)SnxI3 perovskite film.

One-step fabrication of a tunable nanofibrous well insert via electrolyte-assisted electrospinning

One-step fabrication process of a nanofibrous well insert is developed. Both fabrication and integration of the nanofiber membrane on a Transwell insert could be achieved by adopting electrolyte-assisted electrospinning.

Multi-plate, thin-film electrodes of manganese oxide synthesized via the thermal decomposition of a manganese-amine complex for use as electrochemical supercapacitors

Multi-plate, thin-film manganese oxide electrodes were synthesized via the thermal decomposition of a complex of manganese (II) formate (MnF) and triethylenetetramine (TETA) at 260°C. These approximately 200nm thick plates contained 50–100nm nanoparticles and were obtained from a complex of TETA and MnF with a molar ratio of 4. A cyclic voltammetry (CV) test confirmed the pseudocapacitive properties of these multi-plate, thin-film manganese oxide electrodes. The specific capacitance of multi-plate, thin-film electrodes with a mass loading of 10μg was calculated from a CV curve at 10mV/s that reached 938F/g. The specific capacitance degradation was measured via a galvanostatic charge-discharge of 0.5mA/cm2 and was almost stable after 1,000 cycles, which resulted in good cycle stability. Thus, an electrode of non-composite manganese oxide with high specific capacitance and good stability was obtained via a simple one-step fabrication process by thermal decomposition.

Packaged Optical Add-Drop Filter Based on an Optical Microfiber Coupler and a Microsphere

In this letter, a packaged add-drop filter composed of a silica microsphere resonator with a diameter of $80~\mu \text{m}$ and an optical microfiber coupler with a waist diameter of 1 $\mu \text{m}$ is investigated. A one-step fabrication process using UV curable epoxy is shown to stabilize the coupling between the microsphere and the microfiber coupler, which is used for the add and drop ports. The packaged microsphere-microfiber coupler device has a high $Q$ -factor of $1\times 10^{7}$ in the add–drop filter configuration. This device has excellent features, such as improved ease of fabrication, multiple resonant peaks, and high mechanical stability.

A rapid one-step electrodeposition process for fabrication of superhydrobic surfaces on anode and cathode

This work presents a method to solve the weak solubility of zinc chloride (ZnCl2) in the ethanol by adding some reasonable water into an ethanol electrolyte containing ZnCl2 and myristic acid (CH3(CH2)12COOH). A rapid one-step electrodeposition process was developed to fabricate anodic (2.5 min) and cathodic (40 s) superhydrophobic surfaces of copper substrate (contact angle more than 150°) in an aqueous ethanol electrolyte. Morphology, composition, chemical structure and superhydrophobicity of these superhydrophobic surfaces were investigated by SEM, FTIR, XRD, and contact angle measurement, respectively. The results indicate that water ratio of the electrolyte can reduce the required deposition time, superhydrophobic surface needs over 30 min with anhydrous electrolyte, while it needs only 2.5 min with electrolyte including 10 mL water, and the maximum contact angle of anodic surface is 166° and that of the cathodic surface is 168°. Two copper electrode surfaces have different reactions in the process of electrodeposition time, and the anodic copper surface covers copper myristate (Cu[CH3(CH2)12COO]2) and cupric chloride (CuCl); while, zinc myristate (Zn[CH3(CH2)12COO]2) and pure zinc (Zn) appear on the cathodic surface.

Gecko-inspired chitosan adhesive for tissue repair

The advent of nanotechnology has opened the possibility of fabricating nanoscopic pillars on the surface of polymeric films mimicking the Gecko’s foot, in an attempt to increase their adhesive capabilities enhanced by van der Waals forces. However, these forces are considerably weakened in a wet physiological environment. To circumvent this loss in force, current biocompatible adhesives with nanopillars require complex multiple-step fabrication, including an extra layer of adhesive coating to stabilize tissue bonding under physiological conditions. In this report, we describe a simple one-step fabrication process of a single-layer chitosan film that has pillars with base diameter in the range of 100–600 nm and a height of ~70 nm. The nanostructured adhesive is laser-bonded to tissue and does not require pillar coating to enhance bonding in water. In comparison with a ‘flat’ adhesive (without pillars), the nanostructured adhesive bonded significantly stronger to tissue under either stress or pressure. Atomic force spectroscopy also confirmed the superior bonding capability of the nanostructured adhesive. This study demonstrates a one-step fabrication technique to produce a monolayer gecko-inspired adhesive that is biocompatible and bonds effectively to tissue. A gecko-inspired adhesive that retains its adhesion in wet environments and can be easily fabricated has been demonstrated. Gecko-inspired adhesives have strong adhesion due to nanoscale protrusions that maximize the surface area and hence Van der Waals forces, but they tend to lose their sticking power in the wet. Although biocompatible adhesives that are suitable for wet conditions have been produced, they require an extra layer and complex fabrication processes. Now, Antonio Lauto of Western Sydney University in Australia and his co-workers report a single-layer chitosan film with nanoscale pillars that can be fabricated by a simple one-step process involving dry casting. The film bonds strongly to tissue on laser irradiation, making it promising for biomedical applications such as facilitating wound sealing and tissue repair. This study describes a simple one-step fabrication process of a chitosan film that has nanoscale pillars. The adhesive is laser-bonded to tissue and does not require pillar coating to enhance bonding in water. In comparison with a ‘flat’ adhesive without pillars, the nanostructured adhesive bonded significantly stronger to tissue under either stress or pressure. This adhesive combines two mechanisms for tissue bonding: one based on the nanopatterned surface that increases the adhesion strength over short distances (van der Waals and electrostatic interactions) and another based on elastic interaction with polymer chains over much longer distances.

One-step sol–gel imprint lithography for guided-mode resonance structures

Guided-mode resonance (GMR) structures consisting of sub-wavelength periodic gratings are capable of producing narrow-linewidth optical resonances. This paper describes a sol–gel-based imprint lithography method for the fabrication of submicron 1D and 2D GMR structures. This method utilizes a patterned polydimethylsiloxane (PDMS) mold to fabricate the grating coupler and waveguide for a GMR device using a sol–gel thin film in a single step. An organic–inorganic hybrid sol–gel film was selected as the imprint material because of its relatively high refractive index. The optical responses of several sol–gel GMR devices were characterized, and the experimental results were in good agreement with the results of electromagnetic simulations. The influence of processing parameters was investigated in order to determine how finely the spectral response and resonant wavelength of the GMR devices could be tuned. As an example potential application, refractometric sensing experiments were performed using a 1D sol–gel device. The results demonstrated a refractive index sensitivity of 50 nm/refractive index unit. This one-step fabrication process offers a simple, rapid, and low-cost means of fabricating GMR structures. We anticipate that this method can be valuable in the development of various GMR-based devices as it can readily enable the fabrication of complex shapes and allow the doping of optically active materials into sol–gel thin film.