Breath Figure Method Research Articles

Research progress of breath figure method in device application

As a simple, low-cost, green, clean, and efficient method to prepare honeycomb porous membranes, breath figure method has been widely used in biology, medicine, surface science, organic electronics, sensors, electro chemistry and many other fields. This article summarizes the application of breath figure method in these fields in the last 10 years and discuss the influencing factors of breathing figure array. Finally, the research prospects and existing challenges of the breath diagram method are addressed.

Breath figure templated self-assembly of surface-acylated cellulose nanowhiskers confined as honeycomb films

The self-assembly of cellulose nanowhiskers (CNWs) in confined geometries provides a powerful method for the fabrication of novel structures. Herein, ordered honeycomb microporous films were first prepared with surface-acylated CNWs (CNWs-SU) through the breath figure method. Resulting films showed highly porous order over large regions and the iridescent color was only displayed by their rims, which is different from traditional dish-cast CNW films showing the iridescent color over the whole area. This is mainly due to the condensation of water droplets forming three-dimensional (3D) geometry, which forced CNWs-SU to self-assemble into cholesteric architectures in confined geometry and resulted in the iridescent color of the rims after drying. The mechanism was further studied by investigating the critical influencing factors, primarily the concentration of CNW-SU suspensions, the relative humidity of the atmosphere and the surface-attached moieties. In particular, CNW-SU suspensions with a concentration of 3 mg/mL at the relative humidity of 75% preferentially formed honeycomb films with uniform pores. Too low or too high concentrations of CNW-SU suspensions or relative humidity are not preferable for uniform porous films. CNWs-SU with further immobilized octadecane or fluoroalkyl groups on their surface strongly affected the formation of uniform porous films because of higher hydrophobicity and accompanying inhomogeneous condensation of water droplets. This work provides a novel method to study the interactions of CNWs beyond the planar geometry and the formation of uniform porous films solely with CNWs with structural colors open up interesting possibilities for broad application in photonic nanomaterials.Graphic abstract

Photoswitchable Configuration of Nematic Liquid Crystal Droplets Embedded in a Honeycomb‐Patterned Film

AbstractHoneycomb‐patterned polymer films prepared by the breath figure method exhibit unique shape features. These films have potential in various applications, but functional materials are rarely embedded into the arrayed cavity. Here, a photoswitchable function of a compartmented nematic liquid crystal (NLC) in a honeycomb array is proposed. Surface segregation and liquid crystal self‐assembly processes cover curved honeycomb walls of polystyrene (PS) with a high‐density polymer brush of an azobenzene side chain liquid crystalline polymer (SCLCP), producing honeycomb polymer films with isolated cavities. Spherical confinement of the cavities with the SCLC brush provides a bipolar nematic director (planar anchoring), whereas UV light irradiation induces a radial configuration (homeotropic anchoring) of NLC droplets. Photoisomerization of azobenzene UV and visible light irradiation repeatedly induces a photoswitchable change between the bipolar and radial modes.

Nicotinic-Acid-Ornamented Tetrameric Rare-Earth-Substituted Phospho(III)tungstates with the Coexistence of Mixed Keggin/Dawson Building Blocks and Its Honeycomb Nanofilm for Detecting Toxins.

A fascinating class of nicotinic-acid-ornamented tetrameric rare-earth (RE)-substituted phospho(III)tungstates [NH2(CH3)2]10Na4H8[RE2(NA)(HNA)(H2O)6(W2O4)(β-H2P2IIIW13O49)(α-HPIIIW9O33)]2·22 H2O [RE = Nd3+ (1-Nd), Tb3+ (2-Tb), Dy3+ (3-Dy), Ho3+ (4-Ho), HNA = nicotinic acid] were isolated through a one-step reaction method of Na2WO4·2H2O, H3PO3, HNA, NH2(CH3)2·HCl, and RE(NO3)·6H2O. Of meticulous concern is that HPO32- was used as a template to construct tetrameric RE-substituted phospho(III)tungstates including mixed heteropolyoxotungstate building blocks. Their hybrid polyoxoanions are composed of two symmetrical [RE2(NA)(HNA)(H2O)6(W2O4)(β-H2P2IIIW13O49)(α-HPW9O33)]11- units linked by RE-O-W bonds. The symmetrical unit consists of one peculiar heterometal nicotinic-acid-ornamented [RE2(NA)(HNA)(W2O4)]9+ cluster connecting a pentavacant Dawson-like [β-H2P2W13O49]12- and a trivacant Keggin [α-HPW9O33]8- subunits. Furthermore, dimethyldioctadecylammonium chloride (DMDODA·Cl) was used to combine with 1-Nd in the CHCl3-H2O system through electrostatic interactions, leading to the 1-Nd@DMDODA composite material. The honeycomb-patterned film of the 1-Nd @DMDODA composite material was successfully constructed by using the breath figure method on a glassy carbon electrode, which can offer abundant binding sites to Au nanoparticles (nano-Au). Ulteriorly, Au-functionalized 1-Nd@DMDODA-modified electrode was utilized as an electrochemical sensor to detect ochratoxin A, showing a good detection limit of 1.19 pM.

Hexameric to Trimeric Lanthanide-Included Selenotungstates and Their 2D Honeycomb Organic-Inorganic Hybrid Films Used for Detecting Ochratoxin A.

Two types of organic-inorganic hybrid structure-related lanthanide (Ln)-included selenotungstates (Ln-SeTs) [H2N(CH3)2]11Na7[Ce4(H2PTCA)2(H2O)12(HICA)]2[SeW4O17]2[W2O5]4[SeW9O33]4·64H2O (1, H3PTCA = 1,2,3-propanetricarboxylic acid, H2ICA = itaconic acid) and [H2N(CH3)2]6Na4[Ln4SeW8(H2O)14(H2PTCA)2O28] [SeW9O33]2·31H2O [Ln = Pr3+ (2), Nd3+ (3)] were obtained by Ln nature control. The primary frameworks of 1-3 are composed of trivacant Keggin-type [B-α-SeW9O33]8- and [SeW4Om]n- [Ln = Ce3+ (1), m = 17, n = 6; Ln = Pr3+ (2), Nd3+ (3), m = 18, n = 8] fragments bridged by organic ligands and Ln clusters. Intriguingly, Ln nature results in the degradation of hexameric 1 to trimeric 2-3. Besides, 1@DMDSA and 3@DMDSA composites (DMDSA·Cl = dimethyl distearylammonium chloride) were prepared through the cation exchange method, which were then reorganized to form two-dimensional (2D) honeycomb thin films by the breath figure method. Using these honeycomb thin films as electrode materials, the aptasensors were further established by utilizing methylene blue as an indicator and cDNA and Au nanoparticles as signal amplifiers to enhance the response signal so as to realize the purpose of ochratoxin A (OTA) detection. This work provides a new platform for detecting OTA and explores the application potential of POM-based composites in biological and clinical analyses.

Effect of Pore Size of Honeycomb-Patterned Polymer Film on Spontaneous Formation of 2D Micronetworks by Coculture of Human Umbilical Vein Endothelial Cells and Mesenchymal Stem Cells.

The geometrical control of micronetwork structures ( NSs) formed by endothelial cells is an important topic in tissue engineering, cell-based assays, and fundamental biological studies. In this study, NSs are formed using human umbilical vein endothelial cells (HUVECs) by the coculture of HUVECs and human mesenchymal stem cells (MSCs) confined in a honeycomb-patterned poly-l-lactic acid film (honeycomb film (HCF)), which is a novel cell culture scaffold. The HCF is produced using the breath figure method, which uses condensed water droplets as pore templates. The confinement of the HUVECs and MSCs in the HCF along with the application of centrifugal force results in NS formation when the pore size is more than 20 m. Furthermore, NS development is geometrically restricted by the hexagonally packed and connected pores in the horizontal direction of the HCF. Network density is also controlled by changing the seeding density of the HUVECs and MSCs. The threshold pore size indicates that NSs can be formed spontaneously by using an HCF with a perfectly uniform porous structure. This result provides an important design guideline for the structure of porous cell culture scaffolds by applying a blood vessel model in vitro.

Polymer-Based Honeycomb Films on Bioactive Glass: Toward a Biphasic Material for Bone Tissue Engineering Applications.

The development of innovative materials for bone tissue engineering to promote bone regeneration while avoiding fibrous tissue infiltration is of paramount importance. Here, we combined the known osteopromotive properties of bioactive glasses (BaGs) with the biodegradability, biocompatibility, and ease to shape/handle of poly-l-co-d,l-lactic acid (PLDLA) into a single biphasic material. The aim of this work was to unravel the role of the surface chemistry and topography of BaG surfaces on the stability of a PLDLA honeycomb membrane, in dry and wet conditions. The PLDLA honeycomb membrane was deposited using the breath figure method (BFM) on the surface of untreated BaG discs (S53P4 and 13-93B20), silanized with 3-aminopropyltriethoxysilane (APTES) or conditioned (immersed for 24 h in TRIS buffer solution). The PLDLA membranes deposited onto the BaG discs, regardless of their composition or surface treatments, exhibited a honeycomb-like structure with pore diameter ranging from 1 to 5 μm. The presence of positively charged amine groups (APTES grafting) or the precipitation of a CaP layer (conditioned) significantly improved the membrane resistance to shear as well as its stability upon immersion in the TRIS buffer solution. The obtained results demonstrated that the careful control of the substrate surface chemistry enabled the deposition of a stable honeycomb membrane at their surface. This constitutes a first step toward the development of new biphasic materials enabling osteostimulation (BaG) while preventing migration of fibrous tissue inside the bone defect (honeycomb polymer membrane).

Study of the capacity of poly(N‐vinylcarbazole) derivatives to form honeycomb‐like patterns

AbstractPoly(N‐vinylcarbazole), two dihalogenated derivatives, and nanocellulose/poly(N‐vinylcarbazole) nanocomposite thin films have been fabricated with micrometric pore topography. This patterned structure has been developed by using breath figure method, which is an easy and cost‐effective method to obtain honeycomb‐like arrays. In addition, the effect of the dihalogenated substitutions and the presence of nanocellulose fillers in the topography and conformational entropy were evaluated. The conformational entropy of each sample was calculated by using Voronoi tessellation. It is important to notice that highly regular patterns have been obtained from this photoconductive polymer, since the conductivity of this kind of material is proportional to the absorbed light, this honeycomb‐like topography could improve the light capture and the efficiency of photoelectric conversion, increasing the potential applicability of these materials.

Gradient Porous Structure Templated by Breath Figure Method

Surfaces with gradient topography are important in various fields but are difficult to fabricate. Herein, we report a facile and robust way to fabricate a surface with gradient topography of porous structure, in one direction, based on the breath figure (BF) method for the first time. The influencing factors including relative humidity (RH), sample immersion time, and solvent composition, affecting the speed, time, and model of the droplet growth, respectively, were investigated to control gradient BF pores with different ranges of pore sizes. Applying appropriate parameters, gradient BF pores with a diameter difference over 400% were prepared on one sample. The mechanism of gradient duration of solvent evaporation at different regions of a sample for fabricating gradient pores was proposed and experimentally verified with recording optical and thermographic changes of the sample in the BF procedure. This new method provides a novel site for gradient topography fabrication.

Detecting methylphenethylamine vapor using fluorescence aggregate concentration quenching materials

Abstract Organic thin-film fluorescent sensors for vapor with high sensitivity, rapid response, and no pollution to analytes have received widespread attention. However, the development of vapor sensors is very slow. The difficulty lies in most fluorescent materials cannot luminesce in solid state because of ACQ (aggregate concentration quenching) effect. Previous works have usually focused on the design and synthesis of new materials to avoid ACQ effect. Whereas, if existing ACQ materials can be utilized, it will greatly expand the selection range of fluorescent materials used in vapor sensors. In this study, a high-performance vapor sensor utilizing ACQ fluorescent material was successfully prepared based on doping/breath figure method. Firstly, the fluorescence emission of ACQ molecule in solid state was realized by doping with polymer. Then porous sensing film was fabricated via breath figure method (BFs) with large surface-to-volume ratio. Finally, the vapor sensing of ACQ molecule was realized. Herein, the molecule BOR−CHO was selected as ACQ probe doping with polystyrene to get good solid-state luminescence. Then high-quality porous sensing film was obtained by optimizing the BFs parameters. Such a film showed a quick fluorescence quenching response to MPEA (simulant of methamphetamine) gas within 20 s with a detection limit of 1.58 ppm. Our results identify a simple strategy to get enhanced optical intensity of BOR−CHO and achieve superior sensing performance towards MPEA. Most importantly, these findings provide a low-cost method for the facile realization of high surface-to-volume ratio fluorescent sensors for vapor analytes via using ACQ materials, with great flexibility and expandability.

Breath figure‐derived porous fluorine‐containing poly(ether sulfone) membranes with low dielectric constant

AbstractAs an important part of electronic packaging materials, low‐dielectric materials can ensure effective signal transmission between electronic components and have an impact on the performance of microprocessor chips. Herein, a porous poly(ether sulfone) membrane with low dielectric constant is fabricated via a breath figure method to meet requirements for high performance of new packaging materials. Perfluorononyl oxide side groups are introduced into the molecular structure of a block poly(ether sulfone) polymer by post‐grafting, and the pore‐making process and the dielectric properties of the materials are studied. The resulting multi‐block copolymers are found to have different electric and thermal properties depending on the molar ratio of perfluorononyl oxide side groups. Regular honeycomb pores can be formed with a polymer segment length of 8/16. Besides, the porous membranes with ordered pore structure on the surface possess low dielectric constant values ranging from 1.57 to 2.19 at 10 kHz. © 2021 Society of Industrial Chemistry.

Enhancing stability and antioxidant efficacy of fisetin by encapsulating as β-cyclodextrin inclusion complex with porous polylactic acid film from breath figure

This research aims to investigate the scope of fisetin (FIT)/β-cyclodextrin (β-CD) inclusion complexes with the ratios of 1:2 and 2:1 mole by means of freeze-drying, kneading and physical mixing methods (controlled process). Moreover, the complex compounds are analyzed by Fourier-Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC). The results show that the most suitable preparation method of fisetin (FIT)/β-CD complex is the freeze-drying method with the fisetin (FIT) to β-CD ratio at 1:2. The emission of FIT/β-CD was investigated and it is found that the emission rate of freeze-dried FIT/β-CD in 1:2 ratio by freeze-drying method is lower than that by kneading and physical mixing methods. These results lead to an initiation of the innovative active packaging materials with synthetic polylactic acid (PLA) porous film by breath figure (BF) method in order to entrap FIT/β-CD inclusion complex. The honeycomb structure with and without the FIT/β-CD complex were analyzed by Scanning Electron Microscopy (SEM). Thereafter, the effectiveness of Antioxidant Activities (%AA) of the porous PLA films is measured by the anti-oxidation caused by 2,2-diphenyl-1-picrylhydrazyl (DPPH method). The result shows that PLA entrapping complex fisetin is more effective than PLA entrapping pure fisetin, by result of 53.0% and 48.6%, respectively.

Laser-assisted nanowetting (LAN): Hierarchical Nanocomposites containing polymer/gold nanorods on breath figure films

Polymer nanostructures have drawn tremendous interest in recent years owing to their unique properties and widespread applications in various fields. It is still a great challenge, however, to develop novel methods that are capable of preparing hierarchical polymer structures with patterning ability. To conquer this challenge, in this work, we demonstrate the fabrication of hierarchical structures containing polystyrene (PS)/gold nanorods (AuNRs) by combining the modified breath figure method and the laser-assisted nanowetting (LAN) method. PS/PS-AuNRs films are dipped into good/poor solvents (CHCl3/MeOH) mixture solutions using the modified breath figure method to form the porous films with micrometer-sized pores. Subsequently, the porous films are brought in contact with anodic aluminum oxide (AAO) templates and shone by laser beams. The AuNRs then absorb the laser energy and heat the surrounding polymer chains via plasmonic heating, inducing the PS chains to wet the nanopores of the AAO templates. As a result, hierarchical PS/PS-AuNRs films with controlled regions and dimensions can be obtained. This study opens a new research direction for developing hierarchical polymer structures using porous templates.

Biomimetic antibiofouling oil infused honeycomb films fabricated using breath figures

Microorganisms form strong communities known as biofilms, which are ubiquitous in both natural and artificial environments and lead to problems such as health hazards and energy loss. The most effective solution against biofouling is to prevent the initial adhesion of the microbial cells to the material surface. This paper reports the fabrication of slippery liquid-infused porous surfaces (SLIPSs) through a simple method and the antibiofouling properties of these surfaces against microorganisms. The principle of these surfaces is inspired by Nepenthes, which are pitcher plants. SLIPSs can be easily and inexpensively generated through the breath figure method and ultrasonic processing. The developed silicon oil-infused substrate exhibited a low fall angle and antifouling characteristics. The results suggest that the proposed simple method can be used to successfully generate an antibiofouling substrate. A microstructured film was fabricated using the breath figure method, and a slippery surface was achieved by infusing silicone oil onto the film. Among the obtained samples, oil-supported pincushion films (oPCF) most efficiently prevented water droplets and microorganisms from adhering to the surfaces. In addition, the adhesion of E. coli and B. subtilis to oPCF was reduced to 7.1 and 13% of that pertaining to PTFE, respectively. These results suggest that our efficient antifouling substrate can ensure human health and environmental safety without the use of any toxic compounds.

Fabrication of Pore-Selective Metal-Nanoparticle-Functionalized Honeycomb Films via the Breath Figure Accompanied by In Situ Reduction.

Honeycomb films pore-filled with metal (Au, Ag, and Cu) nanoparticles were successfully prepared by combining the breath figure method and an in situ reduction reaction. First, a polyhedral oligomeric silsesquioxane (POSS)-based star-shaped polymer solution containing metal salt was cast under humid conditions for the formation of honeycomb films pore-filled with metal salt through the breath figure method. The morphology of the honeycomb films was mainly affected by the polymer molecular structure and the metal salt. Interestingly, the promoting effect of the metal salt in the breath figure process was also observed. Then, honeycomb films pore-filled with metal nanoparticles were obtained by in situ reduction of the honeycomb films pore-filled with metal salt using NaBH4. Notably, the metal nanoparticles can be selectively functionalized in the pores or on the surface of the honeycomb films by controlling the concentration of the NaBH4. Metal-nanoparticle-functionalized honeycomb films can prospectively be used in catalysis, flexible electrodes, surface-enhanced Raman spectroscopy (SERS), and wettability patterned surfaces.

Fabrication of porous polymer coating layers with selective wettability on filter papers via the breath figure method and their applications in oil/water separation.

A comb-like amphiphilic polymer (PBTF), composed of hydrophobic backbones and hydrophilic side chains, was employed to grow honeycomb coating layers in situ on a filter paper via directly casting a polymer solution and by the subsequent dynamic breath figure (BF) method. Through regulating the hydrophilic polymer side chain density and the solution concentration, a continuous honeycomb coating layer contouring to the filter paper surface profile, in addition to possessing a water contact angle (WCA) as high as 146°, was successfully fabricated. The present study also finds that increasing the hydrophilic side chain density will turn PBTF into a surfactant-like polymer, and thus, endow the PBTF solution with the capacity of numerous micro–nano-sized water droplets, rather than simply stabilizing the ordered water droplet arrays on the surface of the solution. With vast nano-sized water droplets in it, the once transparent PBTF solution changed into a translucent nano-emulsion, which demonstrates a strong Tyndall effect. While casting such nano-emulsion on a filter paper and then subjecting to the BF process, the polymeric solute takes both nano-emulsion intrinsic nano-sized water droplets and solvent evaporation-induced water droplets as templates and self-assembles into a bird-nest-like three-dimensional porous microstructure, which possesses micro–nano-sized communicating pores. By regulating the water content in the nano-emulsion, the bird-nest-like structure can be uniformly formed on the surface of the filter paper, which revealed a WCA of 152°. The coated filter papers possess selective wettability, and meanwhile, maintain the inherent permeability of the substrates, which therefore can be directly utilized as oil/water separation materials.

Preparation of hydrophobic honeycomb films with an amphiphilic copolymer via the breath figure method

Preparation of hydrophobic honeycomb films with an amphiphilic copolymer via the breath figure method

The surface morphology and dynamic impact properties with rebounding and splashing of water droplet on phase separation and breath figure assisted electrospinning films

ABSTRACT Electrospinning provides a versatile, efficient and low-cost method for the preparation of continuous nanofibres from various polymers. In this study, the polyhedral oligomeric silsesquioxanes (POSS) block copolymer was synthesized via atom transfer radical polymerization. The smooth fiber, porous fiber or hierarchically porous microspheres were prepared by electrospinning from POSS block copolymer, poly(vinylidene fluoride) (PVDF) and aluminium oxide (Al2O3). The influence of copolymer concentration, the ratio of the solvents, the diameter and concentration of the Al2O3 on the surface morphology were investigated. Porous fibers and porous microspheres were prepared by regulating the ratio of the solvents from the phase separation and breath figure methods. The dynamic behavior of the water droplet with the constant volume impacting on the electrospinning films were reported. The morphology evolution, restitution coefficient, the change of energy of the water droplets are examined. The droplet bounces several times on the superhydrophobic surface, while the droplet remains pinned and does not rebound when the contact angles was lower than 150°. On the other hand, the water droplets were splashed on the Al2O3 based electrospinning films. Finally, the mechanical properties of the electrospinning films were investigated.

Fabrication of Polypseudorotaxane-Based Responsive Film via Breath Figure Method

Fabrication of Polypseudorotaxane-Based Responsive Film via Breath Figure Method

Preparation of photoactive ZnS-composite porous polymer films: Fluorescent and morphological properties

ABSTRACT This work describes the use of the breath figure (BF) method for the fabrication of photoactive porous polymer films and the characterization of their responsive to photo stimulus. The films incorporate self-assembled photoactive polymers and ZnS nanoparticles (NPs). The effect of both components on the optical and morphological properties of the films were analyzed. Films with a hexagonally ordered pattern were obtained. The photoactive polymer was prepared by grafting the photochromic component 1-(2-hydroxyethyl)-3,3-dimethylindoline-6-nitrobenzopyran (SP) to polystyrene-block-polymethacrylic acid (PS-b-PMMA). ZnS NPs were incorporated into the polymer solution, and the films were prepared using spin-coating on glass substrates before subjecting them to the BF method. The hollow footprints were obtained before introducing the ZnS NPs in order to maintain the necessary conditions for hexagonal film growth. Accordingly, the SEM micrographs of the films prepared in the presence of ZnS NPs displayed a loss in the pore arrangement as a consequence of the interaction between SP moiety and NPs. The light-emitting properties of films were characterized by blue and violet colors when exposed to UV light under fluorescence. Progress in the field of breath-figure formation and its application, such as exemplified in this work, leads to functional structures with suitable applications in chemistry and materials science. It is expected that such microstructured polymeric films will have interesting applications in photonic and optoelectronic devices.