Weihua Ming

Anti-bioadhesion on hierarchically structured, superhydrophobic surfaces

We prepared hierarchically structured, superhydrophobic surfaces, with single-, dual-, and triple-scale roughness, via a layer-by-layer (LbL) particle deposition approach. The dual-/triple-scale structured, superhydrophobic surfaces exhibited significantly reduced protein adsorption (up to a 90% decrease). Furthermore, platelet adhesion and activation was completely suppressed on the triple-scale structured surface.

Dual-Functional Antifogging/Antimicrobial Polymer Coating

Dual-functional antifogging/antimicrobial polymer coatings were prepared by forming a semi-interpenetrating polymer network (SIPN) of partially quaternized poly(2-(dimethylamino)ethyl methacrylate-co-methyl methacrylate) and polymerized ethylene glycol dimethacrylate network. The excellent antifogging behavior of the smooth coating was mainly attributed to the hydrophilic/hydrophobic balance of the partially quaternized copolymer, while the covalently bonded, hydrophobic quaternary ammonium compound (5 mol % in the copolymer) rendered the coating strongly antimicrobial, as demonstrated by the total kill against both Gram-positive Staphylococcus epidermidis and Gram-negative Escherichia coli. The antimicrobial action of the SIPN coating was based on contact killing, without leaching of bactericidal species, as revealed by a zone-of-inhibition test. This type of dual-functional coating may find unique applications where both antimicrobial and antifogging properties are desired.

A simple and effective 1,2,3-triazole based “turn-on” fluorescence sensor for the detection of anions

A novel and effective 1,2,3-triazole based fluorescence chemosensor has been synthesized for the specific detection of anions in homogeneous medium. Notably, the molecule, synthesized in one step using “Click chemistry”, is a simple 1,4-diaryl-1,2,3-triazole, containing a phenol moiety. The probe displayed the strongest response to fluoride ion through the “turn-on” fluorescence sensing mechanism when screened for selectivity and sensitivity against a series of anions (F−, Cl−, Br−, I−, H2PO4−, ClO4−, OAc−, BF4−). Fluorescence spectroscopy and Nuclear Magnetic Resonance Spectroscopy (NMR) studies substantiate 1 : 1 stoichiometry between the probe and fluoride anion. Kinetic studies and the single crystal X-ray spectroscopic evidence revealed the binding interaction occurs with the phenolic group and the anion.

Self-Stratified Antimicrobial Acrylic Coatings via One-Step UV Curing

We designed and synthesized a novel quaternary ammonium methacrylate compound (QAC-2) bearing a perfluoroalkyl tail on one end and an acrylic moiety on the other. Via one-step UV curing of QAC-2 and methyl methacrylate (MMA) with ethylene glycol dimethacrylate (EGDMA) as the cross-linker, we obtained cross-linked coatings with excellent antimicrobial property, as demonstrated by the total kill against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus epidermidis (S. epidermidis) at a QAC-2 concentration as low as ∼0.06 mol % (∼0.4 wt %) relative to MMA, which was substantially lower than the QAC amount needed in the coatings containing QACs with a hydrocarbon tail. A zone of inhibition test confirmed that the antimicrobial effect was on the basis of contact killing and there was no leaching of antimicrobial species from the cross-linked coating. The high antimicrobial potency in QAC-2-containing films was the consequence of strong surface enrichment of the fluorinated QAC, as confirmed by X-ray photoelectron spectroscopy (XPS).

Terpolymer-based SIPN coating with excellent antifogging and frost-resisting properties

We prepared an effective antifogging/frost-resisting coating by forming a semi-interpenetrating polymer network (SIPN) on the basis of a linear, random terpolymer poly(2-(dimethylamino)ethyl methacrylate-co-N-vinylpyrrolidone-co-methyl methacrylate), poly(DMAEMA-co-NVP-co-MMA), and a network of poly(ethylene glycol dimethacrylate). The excellent antifogging/frost-resisting property was mainly attributed to a balanced hydrophilicity/hydrophobicity of the terpolymer with the optimal DMAEMA/NVP/MMA molar ratio at 40/30/30. Compared to our previous work using poly(DMAEMA-co-MMA), the terpolymer-based coating demonstrated excellent antifogging property against both low- and high-temperature moist air, by eliminating the lower critical solution temperature related to the DMAEMA segments in the binary copolymer. By monitoring the coating thickness change during the fogging/frosting test, it appeared that water molecules could rapidly be absorbed into and desorbed from the terpolymer-based coating, implying long-term effectiveness of the antifogging/frost-resisting coating.

Triple-scale structured superhydrophobic and highly oleophobic surfaces

We prepared triple-scale structured, superhydrophobic films via a layer-by-layer particle deposition approach: large silica particles (1.2 μm in diameter) were first partially embedded in an epoxy matrix, followed by electrostatic deposition of medium (180 nm) and small (20 nm) particles. Mechanical robustness of the triple-scale structured coating was enhanced by SiCl4-based cross-linking between silica particles. After chemical modification with a perfluoroalkyl silane, the triple-scale structured surface was turned superhydrophobic, on which the contact angle (CA) and roll-off angle were 167 ± 3° and ∼1° for 10 μL water droplets, and 171 ± 1° and 6 ± 2° for 1 μL water droplets, respectively. The triple-scale surface roughness was especially effective in achieving low roll-off angles for small droplets. The triple-scale structure demonstrated much higher stability for the non-wetting Cassie state for water over a dual-scale structure, as experimentally verified by a compression test. In addition, the triple-scale structured surface was also highly oleophobic, as evidenced by high CAs for hexadecane (134 ± 3°) and ethanol–water mixtures (advancing CA above 150° when the surface tension was greater than 35 mN m−1).

High-efficiency immunoassay platforms with controllable surface roughness and oriented antibody immobilization

High-efficiency immunoassay platforms with controlled surface roughness (single- and dual-scale structured surface) were prepared by combining a facile layer-by-layer particle deposition approach with oriented immobilization of antibodies through boronic acid moieties. The as-prepared surfaces showed significantly enhanced antibody loading capacity and antigen recognition, as proved by fluorescence images.

Antifogging and Frost-Resisting Polymeric Surfaces

Fogging/frosting can significantly reduce clarity of a transparent substrate, resulting in not only inconvenience but also potential danger in daily life. There has therefore been great demand for effective antifogging/frost-resisting surfaces to maintain visibility and transparency in high-humidity environments in a variety of applications. Although tremendous efforts have been made to prepare inorganic antifogging surfaces, the primary focus of this review is on polymeric antifogging/frost-resisting surfaces, as polymer-based antifogging/frost-resisting surfaces hold great promise for large-scale preparation via easily implementable techniques and, subsequently, find more practical applications. In this chapter, recent progress is reviewed in the design, preparation, and typical properties of various antifogging/frost-resisting polymeric surfaces.

Design of polyurethane acrylic antimicrobial films via one-step UV curing

We synthesized two reactive quaternary ammonium methacrylate compounds (QAC-10 and QAC-12) bearing hydrophobic tails with different alkyl chain lengths. Cross-linked films with excellent antimicrobial properties were obtained from a mixture of a polyurethane acrylate prepolymer and a reactive QAC via one-step UV curing. The QAC-containing films showed total kill against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus epidermidis (S. epidermidis) at QAC-12 concentrations as low as ∼2.5 wt% relative to the polyurethane acrylate prepolymer, which was substantially lower than the QAC amount needed in the films containing QAC-10 with a shorter hydrocarbon tail (C10H21). Compared with the QAC-10-containing films, the higher antimicrobial potency in the QAC-12-containing films was the consequence of the longer hydrophobic alkyl tail (C12H25), which offered a stronger driving force for the surface enrichment of the QAC and, thus, greater surface charge density (the longer tail may also penetrate the cell membrane more easily due to stronger hydrophobic interactions). A zone of inhibition test confirmed that the antimicrobial effect of these films was on the basis of contact killing and there was no leaching of antimicrobial species from the cross-linked films.