Chemical Surface Modification Research Articles

Enhancing the mechanical properties of CF-reinforced epoxy composites through chemically surface modification of carbon fibers via novel two-step approach by addition of epichlorohydrin

The chemical surface modification was carried out in this study to improve the interface connection between carbon fiber (CF) and epoxy matrix to study the mechanical and fracture behavior of CF-reinforced epoxy composites. Finite element analysis was carried out by using ABAQUS software to simulate the variation of the tensile strength (TS), interfacial shear strength (IFSS), and interlaminar shear strength (ILSS). The chemical surface modification was carried out by the chemical oxidation by nitric acid and subsequently, addition of monomer resin of epichlorohydrin in a solution at 80 °C. The Raman spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy were carried out to ensure the successful surface modification of CFs. Subsequently, surface-modified CF-reinforced epoxy composites were prepared through the hand lay-up method with the volume fraction of 20 wt.%, and curing was carried out at 80 °C for 4 h. The TS, IFSS, and ILSS values equaled 462.82 MPa, 156 MPa, and 4.1 MPa for modified CF/epoxy composites were achieved, respectively, which are improved remarkably compared to unmodified ones (380, 81, and 2.9 MPa). These improvements are attributed to the successful surface modification of CFs by epichlorohydrin. The surface modification causes the increase in wettability of CFs and the formation of mechanical interlocking and interaction between CFs and epoxy matrix was achieved through uniform and homogenous distribution of epichlorohydrin on the surface of CFs. Fractography was carried out, which indicated the sound and uniform adhesion between CF and epoxy matrix. Achieved results are consistent with simulated results.

Mechanically stable superhydrophobic surfaces constructed by laser surface texturing and micro-arc oxidation of TC4 alloy prepared based on SLM

In this paper, a superhydrophobic surface was prepared on the surface of Ti–6Al–4V (TC4) alloy prepared by selective laser melting (SLM), and the water contact angle (WCA) was 156.8°. The laser surface texturing (LST) and chemical modification treatments were combined with a micro-arc oxidation (MAO) treatment to improve the mechanical durability of the superhydrophobic surface. The surface morphology, wettability, wear resistance, and abrasion resistance of the composite coatings were analyzed, and the mechanism of abrasion resistance on superhydrophobic surfaces was discussed. The superhydrophobic surface that was prepared withstood abrasion under 600 # sandpaper at a pressure of 2.9 kPa and a movement distance of 1020 cm. In addition, the prepared superhydrophobic surface showed better wear resistance and friction reduction in friction experiment, exhibiting more stable coefficient of friction (COF) curve, lower COF value, and narrower abrasion marks. The results show that the prepared composite coatings not only exhibit superhydrophobicity, but also good mechanical stability, which effectively improves the mechanical property of superhydrophobic sample and significantly prolongs its service life in harsh environments. This study provided a new idea and preparation method for the preparation of mechanically stabilized superhydrophobic surface.

Facile chemical surface modification of boron nitride platelets and improved thermal and mechanical properties of their polymer compounds for 2.5D/3D packaging applications

Thermally conductive yet electrically insulative epoxy composites are sought after as encapsulation materials to tackle the heat dissipation challenges in modern electronics. In this work, we developed a novel one-step and facile solvothermal reflux method using a high-boiling-point solvent to surface-modify hexagonal boron nitride (h-BN) with glycine. By refluxing glycine at high temperature, amino functional groups are grafted onto the BN surface, which can enhance the affinity of fillers for epoxy and reduce the interfacial thermal resistance of the filler/epoxy composites. We investigated the mechanism of glycine-grafted layer formation, optimizing reactant mass ratios for enhanced interfacial thermal transport. The resulting BN@G11/epoxy composites exhibit a remarkable thermal conductivity of 1.04 W/mK at 30 wt% modified-BN loading, representing a 477.8 % increase over neat epoxy and 57.5 % higher than h-BN/epoxy composites at equivalent BN filler loading. Additionally, these composites demonstrate improved thermomechanical properties, confirming the strengthened BN/epoxy interface bonding using modified BN fillers. Compared to other surface treatment methods, this solvothermal reflux approach stands out for its scalability and cost-effectiveness. This scalable and eco-friendly innovation presents a competitive strategy for designing polymer-based composites for thermal management, catering to the demands of future 2.5D/3D semiconductor packaging.

Recent advances to engineer tough basalt fiber reinforced composites: A review

AbstractBasalt fibers, known as “green materials without pollution in the 21st century”, have gained widespread attention due to its good mechanical properties. Basalt fiber‐based composites have applications in various fields such as construction, transportation, energy, and protection. However, as an inorganic fiber material, basalt fiber is hard and brittle and prone to catastrophic failure, reducing the safety of the material. Therefore, it is important to strengthen the toughness of basalt fiber‐based composites. This paper reviews the contributions made by researchers in recent years to enhance the toughness of basalt fiber reinforced composites. It mainly focuses on four aspects: physical and chemical modification of fibers surface, mixed application of multiple fibers, different textile and 3D printing technology, and design of biomimetic structures. Through these methods, the toughness of basalt fiber‐reinforced composite materials was increased by 10%–90%. In today's advocacy for green industrial development, the research and application of basalt fibers are very important for advancing the process of green development. These contributions can promote the application of basalt fiber in engineering fields.Highlights Basalt fiber is a green material without pollution. Basalt fiber reinforced composites is the key material for engineering field. Strengthening interfacial adhesion can significantly improve the toughness of composites. Basalt fibers can serve as an alternative to glass fibers in composite materials. The hybridization of basalt fibers with soft fibers can effectively enhance the toughness of composites.

Wettability tuning on stainless steel LIPSS by laser oxidation and its implication on cavitation bubble dynamics

The modification of surface wettability of stainless steel is essential for many biological applications and industrial implementations. Having a hydrophobic or hydrophilic surface is ideal depending on its application. In this study, the wettability tuning of stainless steel was carried out by producing LIPSS at different laser peak energies. Results showed non-significant changes in the periodicity of the ripples, however hydrophilicity increased with greater laser energies. Raman spectroscopy and SED analysis demonstrated the presence of iron oxide peaks and increased oxygen concentration, demonstrating a chemical surface modification governed by oxidation. Transitions from hydrophilic to hydrophobic surfaces were accomplished by ethanolic triethoxyoctylsilane coated LIPSS. Hydrophobicity enhancement was achieved by the adsorption of organic species promoted by the oxide layer at the ripples. The dynamics of cavitation bubbles close to the coated LIPPS were analyzed. A reduction of the main bubble lifetime with hydrophobicity, whereas a delay of collapse time and deformation of the rebound bubble were found. This led to an experiment for erosion testing producing multiple cavitation events. An increment of surface damage area with increased hydrophobicity was observed. This was attributed to longer collapse times of the rebound bubble which led to stronger shockwaves at the samples surface. This work demonstrates a simple method to tune the surface wettability of stainless steel by laser oxidation, which is a crucial factor for applications related to cavitation phenomena.

Unlocking the potential of a chemically modified blue phosphorene as anode materials for high-performance sodium-ion batteries

Blue phosphorene (Blu-Pn) has recently been identified as a new two-dimensional (2D) form of black phosphorus via the epitaxial growth method and has shown the ability to host a substantial amount of Na while serving as an anode in sodium-ion batteries (NIBs). However, its structural instability is an issue that hinders its further exploitability in NIBs. In this paper, we propose to chemically modify the Blu-Pn network by substituting six phosphorus atoms with a carbon source in the form of a C6 ring, constructing a new and robust CP2 nanosheet. Based on the state-of-the-art non-local van der Waals corrected density functional theory and ab initio molecular dynamic (AIMD) simulations, we systematically explore the feasibility of the designed CP2 as a potential anode material for NIBs. Adding a C6 ring in the Blu-Pn lattice reduces its energy gap from 2 eV to 1.3 eV, which disappears after Na adsorption, indicating a conductive character. Attributed to the synergistic effect, the adsorption energy of Na on CP2 nanosheet (−2.22 eV) is greatly decreased in comparison to the pristine carbon source (e.g., graphene with −0.78 eV) and pristine Blu-Pn (−1.85 eV). The Na diffusivity on CP2 at 300 K is predicted to be 4.90 × 10−11 m2/s by AIMD. The specific capacity is up to 604.1 mAh/g, which exceeds that of the commercialized graphite anode (372 mA h/g). Ultimately, the designed electrode provides a small open circuit potential of 0.66 V that falls within a desirable voltage range. This work paves the way for exploring Blu-Pn 2D anode materials for NIBs technology and provides valuable insights into surface chemical modification towards the long-term stability of Blu-Pn.

Physical and Chemical Surface Modification of Recycled Polystyrene Films for Improved Triboelectric Properties

Polystyrene (PS) is a very common material in packaging. In this study, it is recycled by turning it into energy harvesting devices: triboelectric generators. Herein, heat‐pressed films of recycled PS are formed and their surfaces are modified physically and chemically. The triboelectric properties of the films are determined using a dynamic testing machine, and the performance of the triboelectric generators is evaluated with a high‐speed contact–separation system. The developed charge density of the triboelectric generator increases two orders of magnitude—from 0.03 to 1.52 nC cm−2—by combining these surface modification methods. Such high values of charge density enable the production of single material triboelectric generators.

Laser Machining at High ∼PW/cm2 Intensity and High Throughput

Laser machining by ultra-short (sub-ps) pulses at high intensity offers high precision, high throughput in terms of area or volume per unit time, and flexibility to adapt processing protocols to different materials on the same workpiece. Here, we consider the challenge of optimization for high throughput: how to use the maximum available laser power and larger focal spots for larger ablation volumes by implementing a fast scan. This implies the use of high-intensity pulses approaching ∼PW/cm2 at the threshold where tunneling ionization starts to contribute to overall ionization. A custom laser micromachining setup was developed and built to enable high speed, large-area processing, and easy system reconfiguration for different tasks. The main components include the laser, stages, scanners, control system, and software. Machining of metals such as Cu, Al, or stainless steel and fused silica surfaces at high fluence and high exposure doses at high scan speeds up to 3 m/s were tested for the fluence scaling of ablation volume, which was found to be linear. The largest material removal rate was 10 mm3/min for Cu and 20 mm3/min for Al at the maximum power 80 W (25 J/cm2 per pulse). Modified surfaces are color-classified for their appearance, which is dependent on surface roughness and chemical modification. Such color-coding can be used as a feedback parameter for industrial process control.

Enhancing optical biosensing: Comparing two physical treatments for GPTES chemical functionalization of Cyclo-Olefin Copolymer foil

Cyclo-olefin-copolymer (COC) transparent films are currently the best choice for micro-fluidic bio-sensors for point-of-care diagnostic applications using optical signal detection. However, while the optical and mechanical properties of this polymer are extremely good, the adhesion of the bio-probes on this surface is not optimal, due to its chemical structure, that presents only saturated carbon bonds. The deposition of organo-silane molecules on the COC surface is one of the most effective ways to overcome this problem. But, for the surface functionalization, a surface physical treatment is necessary before the chemical modification of the COC surface. In this paper a comparison of the effectiveness of two different physical treatments, oxygen plasma and UV-ozone, is reported. In particular, the exposure time of the UV-Ozone treatment has been selected to avoid the problem of auto-fluorescence of the modified COC surface, that was observed also for relatively short UV exposure (around 10 min). An investigation of the reactive radicals created on the surface after the physical treatments and the following chemical modification with the organo-silane molecule (GPTES) has been performed using X-ray photoemission spectroscopy. The surface energy and morphology of the films have been also measured by contact angle and optical profilometry. Finally, the bio-probes adhesion performances of the COC surfaces obtained with the two physical treatments and the chemical modification were tested in a fluorescence-based assay, using an organic light emission diode to excite the fluorescence. We observed that the UV-ozone treatment allows to obtain a siloxane network with some reactive epoxy radicals on the COC surface, however, their quantity and distribution are less important and homogeneous than in the oxygen plasma treated surfaces.

Multifunctional curcumin-based polymer coating: A promising platform against bacteria, inflammation and coagulation

The extensive use of polymers in the medical field has facilitated the development of various devices and implants, contributing to the restoration of organ function. However, despite their advantages such as biocompatibility and robustness, these materials often face challenges like bacterial contamination and subsequent inflammation, leading to implant-associated infections (IAI). Integrating implants effectively is crucial to prevent bacterial colonization and reduce inflammatory responses. To overcome these major issues, surface chemical modifications have been extensively explored. Indeed, click chemistry, and particularly, copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has emerged as a promising approach for surface functionalization without affecting material bulk properties. Curcumin, known for its diverse biological activities, suffers from low solubility and stability. To enhance its bioavailability, bioconjugation strategy has garnered attention in recent years. This study represents pioneering work in immobilizing curcumin derivative onto polyethylene terephthalate (PET) surfaces, aiming to combat bacterial adhesion, inflammation and coagulation. Before curcumin derivative bioconjugation, a fluorophore, dansyl derivative, was employed in order to monitor and determine the efficiency of the proposed methodology. Previous surface chemical modifications were required for the immobilization of both dansyl and curcumin derivatives. Ultraviolet-Visible (UV-Vis) demonstrated the amidation functionalization of PET surface. Other surface characterization techniques including X-ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflectance Fourier Transformed Infrared (ATR-FTIR), Scanning Electron Microscopy (SEM) and contact angle, among others, confirmed also the conjugation of both dansyl and curcumin derivatives. On the other hand, different biological assays corroborated that curcumin derivative immobilized PET surfaces do not exhibit cytotoxicity effect. Additionally, corresponding inflammation test were performed, indicating that these polymeric surfaces do not produce inflammation and, when curcumin derivative is immobilized, they decrease the inflammation marker level (IL-6). Moreover, the bacterial growth of both Gram positive and Gram negative bacteria were measured, demonstrating that the immobilization of curcumin derivative on PET provided antibacterial properties to the material. Finally, hemolysis rate analysis and whole blood clotting assay demonstrated the antithrombogenic effect of PET-Cur surfaces as well as no hemolysis concern in the fabricated functional surfaces.

Tendon Decellularized Matrix Modified Fibrous Scaffolds with Porous and Crimped Microstructure for Tendon Regeneration.

Current engineered synthetic scaffolds fail to functionally repair and regenerate ruptured native tendon tissues, partly because they cannot satisfy both the unique biological and biomechanical properties of these tissues. Ideal scaffolds for tendon repair and regeneration need to provide porous topographic structures and biological cues necessary for the efficient infiltration and tenogenic differentiation of embedded stem cells. To obtain crimped and porous scaffolds, highly aligned poly(l-lactide) fibers were prepared by electrospinning followed by postprocessing. Through a mild and controlled hydrogen gas foaming technique, we successfully transformed the crimped fibrous mats into three-dimensional porous scaffolds without sacrificing the crimped microstructure. Porcine derived decellularized tendon matrix was then grafted onto this porous scaffold through fiber surface modification and carbodiimide chemistry. These biofunctionalized, crimped, and porous scaffolds supported the proliferation, migration, and tenogenic induction of tendon derived stem/progenitor cells, while enabling adhesion to native tendons. Together, our data suggest that these biofunctionalized scaffolds can be exploited as promising engineered scaffolds for the treatment of acute tendon rupture.

Silk fibroin catheter with stable bioinspired inner-surfaces for inhibition of bioadhesion

Biofilm formation on indwelling medical devices such as catheters and ventilators due to the adhesion of bacteria poses significant challenges in healthcare. Surface modification with micro- and nano-structures offers a promising strategy to prevent bioadhesion and is safer than surface chemical modification approaches. Here, catheters were prepared using silk fibroin (SF) hydrogels and an infusion molding method, with the inner surface featuring a micropapillae structure inspired by lotus leaves (SF-CMP). After phenylethanol (PEA) fumigation treatment, the resulting catheters (SF-CMP PEA) displayed improved swelling resistance and mechanical properties compared to methanol-treated catheters (SF-CMP MeOH). PEA was more efficient than methanol in controlling the size, distribution, and content of silk crystalline β-sheet blocks and thus the swelling and mechanical properties. Moreover, the micro-papillae structure on SF-CMP PEA remained stable over 35 days in solution, in contrast to SF-CMP MeOH, which lasted <7 days. SF-CMP PEA exhibited repellent effects against E. coli and S. aureusin vitro, and low cytotoxicity to the endothelial cells cultured on the unpatterned surface. Additionally, subcutaneous implantation studies showed reduced inflammation around the micropatterned samples compared to controls with a plain, unpatterned surface. The unique properties of SF-based materials, including tunable structures, biocompatibility, degradation, and drug-loading capability make them an attractive material for anti-bioadhesion in applications ranging from indwelling medical devices to tissue engineering scaffolds.

Controlled Wrinkle Patterning on Thin Films to Improve Hydrophobicity.

Controlling surface morphology is one of the main strategies used to tune surface hydrophobic and icephobic properties. Taking advantage of coating growth by initiated chemical vapor deposition, random and ordered wrinkles were induced on a thin film of polyperfluorodecyl acrylate (pPFDA) deposited on polydimethylsiloxane (PDMS) to simultaneously modify surface chemistry and morphology. A range of wrinkles of different wavelengths were studied, and how the wrinkle characteristics change with varying coating thickness. Ordered wrinkles enhanced hydrophobicity more when compared to random wrinkles, with a noticeable effect for coating thickness on the order of hundreds of nanometers. An insight into the mechanism of surface wrinkling and its effect on freezing delay is also provided, and promising results were found on ordered wrinkles, where a freezing delay was observed.

Surface-engineered in-situ fibrillated thermoplastic polyurethane as toughening reinforcement for geopolymer-based mortar

Geopolymer composites often exhibit severe brittle failure when subjected to tensile and flexural loads, mainly owing to their inherently ceramic-like structure. Therefore, this study aims to overcome the previously mentioned weaknesses by introducing 2 wt% of surface-modified, in-situ fibrillated Co-PP (copolymer of polyethylene (PE) and polypropylene (PP))/thermoplastic polyurethane (TPU) blend to produce fiber-reinforced geopolymer mortars. The fiber-in-fiber Co-PP/TPU was first fabricated using spunbond, then functionalized using a mild, two-step, one-pot chemical surface modification process. A comprehensive and detailed study of the fibers' chemical structure, morphology, and mechanical properties has been conducted. As well as their impact on the geopolymer mortars' mechanical performances. Moreover, incorporating the modified fibers dramatically increased the flexural toughness and strength at failure of the composite, reaching up to 1600 % and 280 % compared to the control sample, respectively. Furthermore, the flexural modulus was improved by 2 folds. Additionally, the split tensile and compressive strength were improved by 84 % and 17 %, respectively. These findings and the SEM images of the fractured samples indicate the presence of several toughening mechanisms, associated with an improved matrix-fiber interface and an enhanced growth of geopolymer products around the fiber's surface.

Hydrophobization of Cold Plasma Activated Glass Surfaces by Hexamethyldisilazane Treatment.

The objective of this study was to investigate the modification of glass surfaces by the synergistic combination of cold plasma and chemical surface modification techniques. Glass surface hydrophobicity was obtained as a result of various plasma and deposition operational conditions. The mechanisms governing the hydrophobization process were also studied. Glass plates were activated with plasma using different gases (oxygen and argon) at different treatment times, ranging from 30 to 1800 s. Then, the plasma-treated surfaces were exposed to hexamethyldisilazane vapors at different temperatures, i.e., 25, 60, and 100 °C. Complete characterization, including contact angle measurements, surface free energy calculations, 3D profilometry, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy, was accomplished. It was found that the extent of the hydrophobicity effect depends on both the plasma pre-treatment and the specific conditions of the hexamethyldisilazane deposition process. Plasma activation led to the formation of active sites on the glass surface, which promoted the adsorption and reaction of hexamethyldisilazane species, thereby inducing surface chemical modification. Longer plasma pre-treatment resulted in stronger modification on the glass surface, resulting in changes in the surface roughness. The largest water contact angle of ≈100° was obtained for the surface activated by argon plasma for 1800 s and exposed to hexamethyldisilazane vapors at 25 °C. The changes in the surface properties were caused by the introduction of the hydrophobic trimethylsilyl groups onto the glass surface as well as roughness development.

Advanced film/substrate interface engineering for adhesion improvement employing time- and energy-controlled metal ion irradiation

Pre-deposition substrate etching by metal ion bombardment is an efficient and fast cleaning method that ensures improved chemical and topological substrate surface modification. Here, we study the effects of metal ion mass and kinetic energy on etching of industrially-relevant cemented carbide (WC) substrate as well as on adhesion at the Ti0.50Al0.50N/WC interface. Cr+ or W+ ion fluxes are generated by high-power impulse magnetron sputtering (HiPIMS), while their kinetic energy Ekin is tuned by applying negative substrate bias voltage synchronously with the metal ion-rich portion of the flux. The time evolution of ion fluxes at the substrate plane is studied with energy- and time-resolved ion mass spectrometry. The threshold substrate bias voltage required to initiate substrate etching is in the 900–1000 V range for both Cr+ and W+ fluxes. Moreover, we show that the adhesion strength of Ti0.50Al0.50N coatings correlates with Ekin. For Ekin < 900 eV, Cr or W interlayers are grown and no significant improvement in the adhesion strength is observed. Contrary, for Ekin > 900 eV, effective substrate etching with energetic metal ions significantly improves the adhesion strength: we demonstrate an increase of 76–79 % after etching with metal ions as compared to the untreated substrate.

Enhancing surface morphology, mechanical, and wettability properties of PVA/chitosan/HAp nanofiber scaffold through dielectric barrier discharge plasma treatment

Dielectric barrier discharge (DBD) plasma treatment has been widely used for surface functionalization, allowing for precise modification of surface chemistry and morphology. This study investigates the efficacy of DBD plasma treatment in enhancing the surface morphology and wettability of electrospun nanofiber scaffolds composed of polyvinyl alcohol (PVA), chitosan, and hydroxyapatite (HAp), with potential applications in bone tissue engineering. Scanning electron microscopy (SEM) revealed significant alterations in surface morphology after treatment, including a reduction in average fiber diameter and the presence of uneven, damaged, and even broken fibers. Interestingly, the ultimate strength of the nanofibers increased from 1.13 ± 0.05 MPa to 6.99 ± 0.07 MPa despite the decrease in diameter. Contact angle measurements confirmed a remarkable improvement in wettability, with the contact angle decreasing from 39.46° to 7.45° following increasing treatment time. This enhanced wettability suggests improved cell adhesion, potentially leading to more effective bone tissue regeneration.

Strategies for the quantification and characterization of nanoplastics in AOPs research

There is a growing interest in developing new targeted degradation technologies for the removal of micro- and nanoplastics (NPs) in water, corresponding to increased public concerns regarding their potential negative impacts on urban water systems, and consequently on human life quality. Recently, Advanced Oxidation Processes (AOPs) have been proposed as promising treatment alternatives for effective degradation of NPs in water. However, the selection of appropriate analytical methods for monitoring these oxidation tests remains a challenge. Herein, the feasibility of different characterization strategies for monitoring the evolution of NPs in water upon oxidation tests was systematically studied using polystyrene (PS) NPs of different particle sizes (D0 = 140, 252, 460, and 909 nm) as model plastic pollutants. To quantify NPs in water, Total Organic Carbon (TOC), Chemical Oxygen Demand (COD) and turbidity measurements were assessed. Moreover, turbidity was correlated to the particle size and PS NPs concentration by developing a response surface. Among the analytical techniques employed to characterize the solid particles, transmission electronic microscopy (TEM) was used to evaluate morphology and particle size. Alternatively, the viability of Dynamic Light Scattering (DLS), Nanoparticle Tracking Analysis (NTA) and Atomic Force Microscopy (AFM) to determine particle size is discussed. Chemical surface modifications were explored by Fourier-Transform Infrared Spectroscopy (FTIR). As a proof of concept, the degradation of PS NPs in water upon photo-Fenton oxidation was investigated at ambient conditions and fully characterized using the mentioned techniques.

Insights into the writing process of the mask-free nanoprinting fluid force microscopy technology

Platelets are activated immediately when contacting with non-physiological surfaces. Minimization of surface-induced platelet activation is important not only for platelet storage but also for other blood-contacting devices and implants. Chemical surface modification tunes the response of cells to contacting surfaces, but it requires a long process involving many regulatory challenges to transfer into a marketable product. Biophysical modification overcomes these limitations by modifying only the surface topography of already approved materials. The available large and random structures on platelet storage bags do not cause a significant impact on platelets because of their smallest size (only 1–3 μm) compared to other cells. We have recently demonstrated the feasibility of the mask-free nanoprint fluid force microscope (FluidFM) technology for writing dot-grid and hexanol structures. Here, we demonstrated that the technique allows the fabrication of nanostructures of varying features including grid, circle, triangle, and Pacman-like structures. Characteristics of nanostructures including height, width, and cross-line were analyzed and compared using atomic force microscopy imaging. Based on the results, we identified several technical issues, such as the printing direction and shape of structures that directly altered nanofeatures during printing. Importantly, both geometry and interspace governed the degree of platelet adhesion, especially, the structures with triangular shapes and small interspaces prevent platelet adhesion better than others. We confirmed that FluidFM is a powerful technique to precisely fabricate a variety of desired nanostructures for the development of platelet/blood-contacting devices if technical issues during printing are well controlled.

Dynamic Electrostatic Interfacial Engineering for Block Copolymer Microparticles with Reversible Structures.

Responsive nanoparticle surfactants (NPSs) can dynamically and reversibly modulate the interfacial interactions between incompatible components, which are essential in the interfacial catalysis, corrosion, and self-assembly of block copolymers (BCPs). However, NPSs with stimuli-responsive behavior often involve tedious chemical synthesis and surface modifications. Herein, we propose a strategy to in situ construct a kind of dynamic and reversible NPSs by the interfacial electrostatic interaction between the negatively charged nanoparticles (NPs) and the positively charged homopolymers. The NPSs assembled at the oil/water interface reduce the interfacial tension and direct the confined assembly of BCP. Meanwhile, the dynamic NPSs can be disassembled by increasing the pH value or introducing competitive electrostatic attractions, which can dynamically and reversibly change the interfacial properties as well as the alignment of polymer chains, enabling BCP microparticles with reversibly switchable lamellar and cylindrical structures. Furthermore, by the introduction of aggregation-induced emission luminogens as tails to the NPSs, the reversible transformation of BCP microparticles can be visualized by fluorescence emission, which is dependent on the nanostructures of microparticles. This work establishes a concept for dynamically manipulating interfacial interactions and reversibly switching BCP microparticles without time-consuming NPS synthesis, showing promising applications in the fabrication of smart materials with switchable structures and properties.