Liping Fang

Hierarchical polymer brush nanoarrays: a versatile way to prepare multiscale patterns of proteins.

This paper presents a versatile way to prepare multiscale and gradient patterns of proteins. The protein patterns are fabricated by conjugating proteins covalently on patterns of polymer brush that are prepared by techniques combining colloidal lithography with photolithography, and two-step colloidal lithography. Taking advantages of this technique, the parameters of protein patterns, such as height, diameters, periods, and distances between two dots, can be arbitrarily tuned. In addition, the protein patterns with varies of architectures, such as microdiscs, microstripes, microrings, microtriangles, microgrids, etc., consisting of protein nanodots, are prepared and the sample size is up to 4 cm(2). The as-prepared patterns of fibronectin can promote the cell adhesion and cell location.

Elliptical Polymer Brush Ring Array Mediated Protein Patterning and Cell Adhesion on Patterned Protein Surfaces

This paper presents a novel method to fabricate elliptical ring arrays of proteins. The protein arrays are prepared by covalently grafting proteins to the polymer brush ring arrays which are prepared by the techniques combining colloidal lithography dewetting and surface initiated atom-transfer radical polymerization (SI-ATRP). Through this method, the parameters of protein patterns, such as height, wall thickness, periods, and distances between two elliptical rings, can be finely regulated. In addition, the sample which contains the elliptical protein ring arrays can be prepared over a large area up to 1 cm(2), and the protein on the ring maintains its biological activity. The as-prepared ring and elliptical ring arrays (ERAs) of fibronectin can promote cell adhesion and may have an active effect on the formation of the actin cytoskeleton.

Polymer brush nanopatterns with controllable features for protein pattern applications

A novel technique is reported for preparing wafer-scale polymer brush nanopatterns by combining colloidal lithography with surface-initiated atom-transfer radical polymerization. The nanoarchitecture parameters of the polymer patterns can be fully controlled by tuning the experimental conditions and polymer nanopatterns with a lateral resolution down to 100 nm are successfully achieved. In addition, by coupling this technique with photolithography, hierarchical polymer brush nanopatterns have been fabricated. Significantly, the influences of nanodot morphologies on the feature sizes of the polymer nanopatterns are explained in detail. More importantly, complex protein patterns are prepared by conjugating proteins on the polymer brush nanopatterns. The proteins are covalently immobilized on the polymers and exhibit 3D distribution without denaturation. Cells can adhere quickly to the fibronectin patterns and elongate along the stripes of the protein patterns.

Tunable Polymer Brush/Au NPs Hybrid Plasmonic Arrays Based on Host−guest Interaction

The fabrication of versatile gold nanoparticle (Au NP) arrays with tunable optical properties by a novel host-guest interaction are presented. The gold nanoparticles were incorporated into polymer brushes by host-guest interaction between β-cyclodextrin (β-CD) ligand of gold nanoparticles and dimethylamino group of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). The gold nanoparticle arrays were prepared through the template of PDMAEMA brush patterns which were fabricated combining colloidal lithography and surface-initiated atom-transfer radical polymerization (SI-ATRP). The structure parameters of gold nanoparticle patterns mediated by polymer brushes such as height, diameters, periods and distances, could be easily tuned by tailoring the etching time or size of colloidal spheres in the process of colloidal lithography. The change of optical properties induced by different gold nanoparticle structures was demonstrated. The direct utilization of PDMAEMA brushes as guest avoids a series of complicated modification process and the PDMAEMA brushes can be grafted on various substrates, which broaden its applications. The prepared gold naoparticle arrays are promising in applications of nanosensors, memory storage and surface enhanced spectroscopy.

The fabrication of long-range ordered nanocrescent structures based on colloidal lithography and parallel imprinting

A method for fabricating nanocrescent structures is presented based on a combination of colloidal lithography and parallel imprinting. In this process, non-close-packed colloidal spheres were prepared by a simple lift-up soft lithography technique, and subsequently the individual particles were used as shadow masks to angle deposit a layer of silver on the silicon substrates. Then, the silver-coated samples were etched to get silicon crescent nanohole arrays, which served as templates to mold patterned photocurable resin membranes. The patterned photocurable resin membranes were used to print gold nanocrescent nanostructures onto glass substrates. The size of the opening and the width of the gold nanostructures could be freely adjusted by changing the azimuth angle and tilt angle. Very importantly, the central angle of the nanocrescents could be adjusted in the range of 0°-360°. This method provides a low-cost and highly reproducible way to prepare complex nanostructure arrays for applications related to near field enhancement materials, optical sensors and surface-enhanced Raman spectroscopy, etc.

Hierarchical-Multiplex DNA Patterns Mediated by Polymer Brush Nanocone Arrays That Possess Potential Application for Specific DNA Sensing

This paper provides a facile and cost-efficient method to prepare single-strand DNA (ssDNA) nanocone arrays and hierarchical DNA patterns that were mediated by poly(2-hydroxyethyl methacrylate) (PHEMA) brush. The PHEMA brush nanocone arrays with different morphology and period were fabricated via colloidal lithography. The hierarchical structure was prepared through the combination of colloidal lithography and traditional photolithography. The DNA patterns were easily achieved via grafting the amino group modified ssDNA onto the side chain of polymer brush, and the anchored DNA maintained their reactivity. The as-prepared ssDNA nanocone arrays can be applied for target DNA sensing with the detection limit reaching 1.65 nM. Besides, with the help of introducing microfluidic ideology, the hierarchical-multiplex DNA patterns on the same substrate could be easily achieved with each kind of pattern possessing one kind of ssDNA, which are promising surfaces for the preparation of rapid, visible, and multiplex DNA sensors.

Functional interface based on silicon artificial chamfer nanocylinder arrays (CNCAs) with underwater superoleophobicity and anisotropic properties

A functional interface based on silicon chamfer nanocylinder arrays (CNCAs) was successfully fabricated by carrying out secondary etching of silicon nanopillar arrays via a facile inclined etching method. The structure of the novel CNCAs was finely modulated by varying the nanopillar array structure and the etching conditions. The underwater oil wetting behavior of this CNCAs-based interface can be easily modulated from superoleophilic (oil contact angle (OCA) of ~8.13°) state to superoleophobic (OCA of ~163.79°) state by modifying the surface using different substances. Moreover, a reversible transformation of underwater oil wetting behavior from superoleophobic (OCA of ~155.67°) state to oleophilic (OCA of ~31.27°) state was achieved by grafting a temperature-responsive polymer onto this specific asymmetric structure. The functional interface exhibited isotropic wetting behavior under certain oleophilic conditions. Chemically heterogeneous structures, obtained via asymmetry modification of CNCAs, exhibited amphiphobic properties while maintaining their anisotropic wetting ability.

From 1D to 3D: a new route to fabricate tridimensional structures via photo-generation of silver networks

A rapid and cost effective method has been developed to fabricate 3 dimensional (3D) ordered structures by photo-generating silver networks inside a 1D layered heterogeneous laminate composed of poly(vinyl alcohol) (PVA) and poly(methyl methacrylate) (PMMA). By designing the photo-mask meticulously, the silver nanoparticles (NPs) produced by UV light aggregate to form frameworks in different forms, which perform as the anisotropic component, i.e. the building blocks, thus converting the 1D structure into 3D. Formation of silver NPs increases the refractive index (RI) of the PVA layers, thus bringing optical change to the 1D laminar structure, which allows us to trace the silver formation process by measuring the change of RI value and reflectance spectra. The 1D layered structure is a good building matrix for 3D construction because the total number of layers and the layer thickness can be finely tuned flexibly which allow us to further study the various properties caused by the structural modulation. By utilizing photo-reactive silver ions, an innovative strategy of fabricating 3D structures through in situ photo-generating silver building blocks inside the laminar matrix is established, which makes it possible to fabricate 3D micro/nano composite materials with potential applications in fields such as sensors and photonic meta-materials.

Highly sensitive deep-silver-nanowell arrays (d-AgNWAs) for refractometric sensing

Large-area deep-silver-nanowell arrays (d-AgNWAs) for plasmonic sensing were manufactured by combining colloidal lithography with metal deposition. In contrast to most previous studies, we shed light on the outstanding sensitivity afforded by deep metallic nanowells (up to 400 nm in depth). Using gold nanohole arrays as a mask, a silicon substrate was etched into deep silicon nanowells, which acted as a template for subsequent Ag deposition, resulting in the formation of d-AgNWAs. Various geometric parameters were separately tailored to study the changes in the optical performance and further optimize the sensing ability of the structure. After several rounds of selection, the best sensing d-AgNWA, which had a Ag thickness of 400 nm, template depth of 400 nm, hole diameter of 504 nm, and period of 1 μm, was selected. It had a sensitivity of 933 nm·RIU–1, which is substantially higher than those of most common thin metallic nanohole arrays. As a proof of concept, the as-prepared structure was employed as a substrate for an antigen-antibody recognition immunoassay, which indicates its great potential for label-free real-time biosensing.

Large-scale Au nanoparticle cluster arrays with tunable particle numbers evolved from colloidal lithography

The assembly of metal nanoparticles (NPs) can regulate their plasmon resonance properties to pursue the best properties for applications. However, the controllable assembly of large-scale metal NP cluster arrays remains a significant challenge. This paper presents a novel strategy to prepare large-scale Au NP cluster arrays based on colloidal lithography and template-guided self-assembly technique. The NPs arrays are fabricated by introducing Au NPs onto the quaternized poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) brush templates via electrostatic interaction. The number of Au NPs in cluster can be arbitrarily tuned by changing the surface area of the polymer templates created by colloidal lithography, which resulted in tunable plasmonic properties. The prepared Au NP cluster arrays were used for surface enhanced Raman scattering (SERS) and the SERS properties of the Au NP cluster arrays were studied.