Xueyong Wei

Lipid-AuNPs@PDA nanohybrid for MRI/CT imaging and photothermal therapy of hepatocellular carcinoma.

Multifunctional theranostic nanoparticles represent an emerging agent with the potential to offer extremely sensitive diagnosis and targeted cancer therapy. Herein, we report the synthesis and characterization of a multifunctional theranostic agent (referred to as LA-LAPNHs) for targeted magnetic resonance imaging/computed X-ray tomography (MRI/CT) dual-mode imaging and photothermal therapy of hepatocellular carcinoma. The LA-LAPNHs were characterized as having a core-shell structure with the gold nanoparticles (AuNPs)@polydopamine (PDA) as the inner core, the indocyanine green (ICG), which is electrostatically absorbed onto the surface of PDA, as the photothermal therapeutic agent, and the lipids modified with gadolinium-1,4,7,10-tetraacetic acid and lactobionic acid (LA), which is self-assembled on the outer surface as the shell. The LA-LAPNHs could be selectively internalized into the hepatocellular cell line (HepG2 cells) but not into HeLa cells due to the specific recognition ability of LA to asialoglycoprotein receptor. Additionally, the dual-mode imaging ability of the LA-LAPNH aqueous solution was confirmed by enhanced MR and CT imaging showing a shorter T1 relaxation time and a higher Hounsfield unit value, respectively. In addition, the LA-LAPNHs showed significant photothermal cytotoxicity against liver cancer cells with near-infrared irradiation due to their strong absorbance in the region between 700 and 850 nm. In summary, this study demonstrates that LA-LAPNHs may be a promising candidate for targeted MR/CT dual-mode imaging and photothermal therapy of hepatocellular carcinoma.

A net-shape fabrication process of alumina micro-components using a soft lithography technique

Microceramic components have outstanding properties, such as high temperature resistant, biocompatible, chemically stable and high hardness properties, and could be used in a wide range of applications. However, the fabrication of precision micro-components has long been a barrier and limited their applications. This paper presents a soft lithography technique to fabricate near net-shape alumina micro-components. The process uses elastomer polydimethysiloxane (PDMS) to replace traditional solid moulds and leaves the green patterns intact after demoulding. The whole soft lithography technique involves the following steps: (i) fabricating high aspect ratio SU-8 moulds using UV photolithography, (ii) producing PDMS soft moulds from SU-8 masters, (iii) making aqueous high solids loading alumina suspension, (iv) filling patterned PDMS mould with the aqueous alumina suspension and (v) demoulding and sintering. The rheological properties (zeta potential and viscosity) of aqueous alumina suspensions have been characterized in relation to the varying pH values and concentration of dispersant (D-3005). The optimal parameters of alumina suspension for mould filling have been achieved at a pH value = 11; concentration of dispersant = 0.05 g ml−1; amount of binder = 0.75%; highest solid loading = 70 wt%. After pressurized mould filling, complete, dense and free-standing micro-components have been achieved by using a 70 wt% alumina suspension and an optimum fabrication technique, while the overall linear shrinkage is found to be about 22%.

Large-scale fabrication of ordered metallic hybrid nanostructures

A low-cost and high-throughput method for the fabrication of large-area ordered hybrid metallic nanostructure arrays is presented. Each structure unit is a nanobowl with a hexagonal distributed pillar array upon it. A self-assembled monolayer of polystyrene (PS) nanospheres is used as a template. After thermal evaporation, electroforming and removal of the nanospheres and the conductive layer, ordered arrays of hybrid nickel nanostructures have been fabricated. Both nanobowl arrays and pillar arrays exhibit uniform sizes. Smooth interior surfaces were observed in the nanobowl arrays. The geometry of the structure can be tuned by controlling the thickness of the conductive layer. The approach presented in this paper can be extended to fabricate ordered hybrid nanostructures of a wide range of metals and alloys with controlled size.

Temperature dependent electrical resistivity of a single strand of ferromagnetic single crystalline nanowire

We have measured the electrical resistivity of a single strand of a ferromagnetic Ni nanowire of diameter 55 nm using a four-probe method in the temperature range 3–300 K. The wire used is chemically pure and is a high quality oriented single crystalline sample in which the temperature independent residual resistivity is determined predominantly by surface scattering. Precise evaluation of the temperature dependent resistivity (ρ) allowed us to identify quantitatively the electron-phonon contribution (characterized by a Debye temperature θR) as well as the spin-wave contribution, which is significantly suppressed upon size reduction.

Nonlinear Dynamics of a Periodically Driven Duffing Resonator Coupled to a Van der Pol Oscillator

We explore the dynamics of a periodically driven Duffing resonator coupled elastically to a van der Pol oscillator in the case of 1?:?1 internal resonance in the cases of weak and strong coupling. Whilst strong coupling leads to dominating synchronization, the weak coupling case leads to a multitude of complex behaviours. A two-time scales method is used to obtain the frequency-amplitude modulation. The internal resonance leads to an antiresonance response of the Duffing resonator and a stagnant response (a small shoulder in the curve) of the van der Pol oscillator. The stability of the dynamic motions is also analyzed. The coupled system shows a hysteretic response pattern and symmetry-breaking facets. Chaotic behaviour of the coupled system is also observed and the dependence of the system dynamics on the parameters are also studied using bifurcation analysis.

The fabrication of high-aspect-ratio, size-tunable nanopore arrays by modified nanosphere lithography

A modified nanosphere lithographic process for producing high aspect ratio and size-tunable nanopore arrays is described. A self-assembled bilayer nanosphere template is created as an etch mask for a deep reactive ion etching (DRIE) process. The size of the nanopores is tuned by reducing the diameter of the top-layer nanospheres using oxygen etching. Nanopore arrays with mean in-plane widths ranging from 120.9 to 343 nm and depths up to 2 microm have been achieved. This process offers excellent control over the nanopore size, aspect ratio and pitch of the fabricated nanostructures. The approach can also be extended to fabricate nanopore arrays of a wide range of materials.

Phase noise analysis of a mechanical autonomous impact oscillator with a MEMS resonator

In this paper, phase noise analysis of a mechanical autonomous impact oscillator with a MEMS resonator is performed. Since the circuit considered belongs to the class of hybrid systems, methods based on the variational model for the evaluation of either phase noise or steady state solutions cannot be directly applied. As a matter of fact, the monodromy matrix is not defined at impact events in these systems. By introducing saltation matrices, this limit is overcome and the aforementioned methods are extended. In particular, the unified theory developed by Demir is used to analyze the phase noise after evaluating the asymptotically stable periodic solution of the system by resorting to the shooting method. Numerical results are presented to show how noise sources affect the phase noise performances.

Fabrication of Nickel Nanostructure Arrays Via a Modified Nanosphere Lithography

In this paper, we present a modified nanosphere lithographic scheme that is based on the self-assembly and electroforming techniques. The scheme was demonstrated to fabricate a nickel template of ordered nanobowl arrays together with a nickel nanostructure array-patterned glass substrate. The hemispherical nanobowls exhibit uniform sizes and smooth interior surfaces, and the shallow nanobowls with a flat bottom on the glass substrate are interconnected as a net structure with uniform thickness. A multiphysics model based on the level set method (LSM) was built up to understand this fabricating process by tracking the interface between the growing nickel and the electrolyte. The fabricated nickel nanobowl template can be used as a mold of long lifetime in soft lithography due to the high strength of nickel. The nanostructure–patterned glass substrate can be used in optical and magnetic devices due to their shape effects. This fabrication scheme can also be extended to a wide range of metals and alloys.

Thick photoresists for electroforming metallic microcomponents

Recently, microelectroforming has been extensively applied to fabricating metallic components for sensors, actuators, and other systems. Thick photoresists are used for making micromoulds for electroforming and closely related to the quality and costs of an electroforming process. In the current paper, thick UV photoresists SU8, BPR100, and KMPR are analysed and compared in their electroforming performance of nickel microcomponents. Optimized UV lithography processes are introduced for producing micromoulds in each of the resists and scanning electron microscope (SEM) images of the moulds are presented and analysed. Then, electroformed nickel components from the micromoulds are presented. Finally, applicability of the photoresists to electroforming microcomponents is discussed. Each of the resists demonstrates advantages and disadvantages to suit different applications.

Study of ZnS Nanostructures Based Electrochemical and Photoelectrochemical Biosensors for Uric Acid Detection

Uric acid (UA) is a kind of purine metabolism product and important in clinical diagnosis. In this work, we present a study of ZnS nanostructures-based electrochemical and photoelectrochemical biosensors for UA detection. Through a simple hydrothermal method and varying the ratio of reaction solvents, we obtained ZnS nanomaterials of one-dimensional to three-dimensional morphologies and they were characterized using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). To fabricate the UA biosensor and study the effect of material morphology on its performance, ZnS nanomaterials were deposited on indium tin oxide (ITO) conducting glass and then coated with uricase by physical absorption. Three kinds of working electrodes were characterized by cyclic voltammetry method. The effect of material morphology on performance of UA detection was investigated via amperometric response based electrochemical method based on enzymatic reaction. The ZnS urchin-like nanostructures electrode shows better sensitivity compared with those made of nanoparticles and nanoflakes because of its high surface-area-to-volume ratio. The photoelectrochemical method for detection of UA was also studied. The sensitivity was increased 5 times after irradiation of 300 nm UV light. These results indicate that ZnS nanostructures are good candidate materials for developing enzyme-based UA biosensors.