International Journal of Nanotechnology (19 papers in press)
Fabrication of super hydrophobic duo-structures
by X.Y. Zhang
A RFID-based wireless NH3 gas detector using spin coated carbon nanotubes as sensitive layer
by Ngan Nguyen Le, Eric Fribourg-Blanc, Hue Cam Thi Phan, Dung My Thi Dang, Chien Mau Dang
Abstract: A radio frequency identification (RFID)-based wireless ammonia (NH3) gas detector was developed to work at 868 MHz. Using carbon nanotubes (CNT) thin film as a sensitive layer, a standard RFID tag is transformed into an RFID gas detector. First, RFID copper antenna on flexible polyethylene terephthalate (PET) substrate was fabricated by combining inkjet printing and copper electroplating. After that, CNT thin film was deposited on RFID antenna by spin coating method. RFID chip AK3 tagsys loop was attached with RFID antenna to form RFID tag. Performance of this gas detector was tested by measuring impedance of the RFID antenna and read-range of the RFID tag before and after being submitted to NH3 gas. The impedance of CNT thin film changed in presence of ammonia, leading to a decrease of the RFID tag read-range. A low-cost passive RFID gas detector is demonstrated with good response to NH3gas down to 10 ppm, the RFID tag read-range was decreased from 2.5 m to 1.9 m. Besides, the impedance of RFID antenna had shown the good change, from 11.70 - j20.70 to 8.56 - j33.45 after being exposed 1 min to NH3 gas. From this result, this wireless gas detector is promising to be applied in real life to detect gas leakage, especially in relatively harsh and non-light-of-sight environments, because of many advantages such as low-cost, wireless and easy to control.
Keywords: wireless gas detector; radio frequency identification; RFID; carbon thin film; ammonia; flexible substrate.
Z-axis tuning fork gyroscope having a controlled anti-phase and freestanding architecture: design and fabrication
by Minh Ngoc Nguyen, Long Quang Nguyen, Nhat Sinh Ha, Hoang Manh Chu, Hung Ngoc Vu, Trinh Duc Chu
Abstract: This paper reports the design and fabrication of a z-axis tuning fork gyroscope (TFG) having anti-phase controlled and freestanding architectures. The gyroscope is designed to suppress the in-phase sensing mode by using a self-rotation ring. To improve the performance of the TFG by limiting the influence of the squeeze-film damping, the driving and sensing parts of the gyroscope were designed to oscillate in plane. Furthermore, by removing the substrate underneath the device, the slide-film damping in the gap between the proof masses and the substrate is eliminated. The proposed architecture is analysed by finite element method using ANSYS software. The simulated frequencies of the driving and sensing modes are 9.788 kHz and 9.761 kHz, respectively, which determines the sensor bandwidth of 27 Hz. The frequency difference between the driving and sensing modes and the parasitic ones is obtained to be 57.5%. The sensing displacement and driving displacement of the gyroscope at resonance are 0.104 μm and 6.034 μm, respectively. The gyroscope was fabricated based on the bulk micromachining technology. It is shown that the quality factor of the gyroscope is 111.2. The measured sensitivity of the sensor is evaluated to be 11.56 mV/°/s.
Keywords: bulk micromachining; vibratory gyroscope; tuning fork; FEM; finite element analysis.
Fluidic platform with embedded differential capacitively coupled contactless conductivity detector for micro-object sensing
by Loc Quang Do, Tung Thanh Bui, Ha Thuy Thi Tran, Katsuya Kikuchi, Masahiro Aoyagi, Trinh Chu Duc
Abstract: In this paper, we present a microfluidic platform with differential capacitively coupled contactless conductivity detection (DC4D) technique for microparticle detection. The microfluidic platform is formed by bonding PDMS channel to glass substrate. The proposed microfluidic sensor embedded in the microchannel consists of three adjacent electrodes. These electrodes are arranged to form differential coplanar capacitor structures to provide high sensitivity. The differential capacitance is changed when a microsized object crosses the sensing area in the microfluidic channel. This microfluidic system with the novel sensing design based on DC4D technique provides a platform for detection the presence of an object as well as its electrical property.
Keywords: microfluidic platform; cell detection; capacitive sensing.
Filtration of circulating tumour cells MCF-7 in whole blood using non-modified and modified silicon nitride microsieves
by Thien Dien To, An Thu Thi Truong, Anh Tuan Nguyen, Tin Chanh Duc Doan, Chien Mau Dang
Abstract: Circulating tumour cells (CTCs) are extremely rare cancer cells in blood stream. The detection of CTCs is an important marker in understanding metastatic risk, disease progression and treatment efficacy. In this study, SiN microsieves were used for detection and capture of MCF-7 cells from whole blood samples based on specific binding of the antibody and size of cells. In the first experiments, the non-modified SiN microsieves were used to capture the MCF-7 cells in phosphate-buffered saline (PBS), whole blood which was incubated with monoclonal anti-cytokeratin - FITC (MACF) antibody, herein the antibody had a specific affinity with MCF-7 cells. MCF-7 cells were captured on the microsieve thanks to their larger size, whereas the smaller blood cells could be discarded. In the second experiments, the SiN microsieves were modified with (3-aminopropyl)triethoxysilane (APTES), glutaraldehyde (GTA) and immobilised with MACF antibody. In this case, MCF-7 cells in PBS, whole blood were filtered directly through the modified SiN microsieves. MCF-7 cells were captured selectively basing on size of cells and the specific antibody binding. After cell filtration, the fluorescent microscopy was used to detect MCF-7 cells on the SiN microsieves in both experiments. This is the first report to demonstrate that the SiN microsieves with surface modification could be used to capture MCF-7 breast cancer cells in human whole blood.
Keywords: silicon nitride microsieves; surface modification; glutaraldehyde; APTES; MCF-7; breast cancer; filtration.
Recent advances in the development of micropumps, microvalves and micromixers and the integration of carbon electrodes on centrifugal microfluidic platforms
by Mohammad Mahdi Aeinehvand, Fatimah Ibrahim, Wisam Al-Faqheri, Karunan Joseph, Marc J. Madou
Abstract: Centrifugal microfluidics is a field that has attracted many researchers over the last two decades and its application to biomedical analysis has been investigated intensively. This review paper presents recently developed innovative micropumps, microvalves and micromixers on microfluidic CDs that enabled the automation and integration of sequential bioanalytical assays. We also introduce and compare recent innovations in sensing and detection approaches in centrifugal microfluidic platforms. In this context, we propose the integration of carbon interdigitated electrode arrays (C-IDEAs) biosensors and microballoon fluidic components for the future development of highly sensitive, inexpensive and low-power consuming point-of-care (POC) diagnostic devices. To enable power on the CDs for the C-IDEAs biosensors, we review different formats for transferring power to the spinning platforms.
Keywords: centrifugal microfluidics; microfluidic compact-disc; microballoon; carbon interdigitated electrode arrays biosensor; optical biosensor; redox amplification; point-of-care diagnostic device; spin-stand; electrochemical.
Effect of ultraviolet/ozone treatment on the structural and electrical properties of solution-processed piezoelectric thick-film lead-zirconium-titanate
by Phan Trong Tue
Abstract: In this work, the impact of ultraviolet/ozone (UV/O3) treatment on the structural and electrical properties of solution-processed thick-film lead-zirconium-titanate (PZT) was systematically investigated. Highly (111)-oriented PZT film was observed together with minor phases originated from (100) and (101) orientations. Improvements of electrical properties such as leakage current and hysteresis loop were obtained as well. It is believed that the UV/O3 treatment could facilitate decomposition and oxidation processes of PZT film at a gel state, which leads to suppression of impurities (such as carbon and hydroxide) in the resultant film. As a result, a compacted and high-density PZT film could be achieved. The result enables the use of low-cost and environment-friendly solution-processed PZT film for various applications instead of using conventional high-cost vacuum-based process.
Keywords: lead-zirconium-titanate (PZT) film; solution process; UV/O3 treatment; piezoelectric film.
One-step hydrothermal synthesis of titanium dioxide decorated on reduced graphene oxide for dye-sensitised solar cells application
by Foo Wah Low, Chin Wei Lai, Sharifah Bee Abd Hamid
Abstract: Dye-sensitised solar cells (DSSCs) are one of the promising prospects for efficient renewable resources. To bring DSSCs to the point of commercial readiness and viability in terms of performance and cost, substantial research on the development of a high efficiency DSSCs system is necessary. Our recent studies have indicated that a maximum conductivity of 29.1 µS/cm and conversion efficiency of 4.76% under 1.5 AM condition was successfully achieved from 0.2 wt% TiO2 loaded on reduced graphene oxide (rGO) forming a nanocomposite film, which is approximately twice or three times higher than that of pure rGO nanosheets and anatase TiO2 film. The findings were mainly attributed to the fact that rGO nanosheets could further increase the photo-induced electron transportation rate and minimise the recombination losses within the TiO2 lattice in this binary hybrid photoelectrode.
Keywords: reduced graphene oxide; rGO; titanium dioxide; rGO-TiO2 nanocomposite; dye-sensitised solar cells; DSSCs.
Reduction of isotropic etch for silicon nanowires created by metal assisted deep reactive ion etching
by Tung Thanh Bui, Chien Mau Dang
Abstract: Silicon nanowires were created by deep reactive ion etching (DRIE) using gold nanoparticles as a mask. Gold nanoparticle masks were created by rapid thermal annealing of an evaporated gold thin film. By using different inert gases for the annealing process, many shapes of Au NPs were created including sphere and hemisphere. Parameters such as the gold nanoparticles' shape as well as the DRIE bias voltage were studied to form highly vertical silicon nanowires while ensuring the smallest possible isotropic etch.
Keywords: Si NWs; deep reactive ion etching; DRIE; Au NPs; isotropic etching; bias voltage.
Synthesis of zinc oxide/graphene oxide nanocomposite material for antibacterial application
by Le Thanh Trinh, Le Anh Bao Quynh, Nguyen Huu Hieu
Abstract: In this study, graphene oxide (GO) was prepared by a modified Hummers' method and ZnO/GO was synthesised by coprecipitation. The structural and morphological properties of ZnO/GO nanocomposite were characterised by using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) method, and Raman spectroscopy. The characterisation results show that ZnO nanoparticles with a mean size of 14-26 nm were synthesised and randomly decorated on the surfaces and edges of GO sheets. In addition, the antimicrobial activities of GO and ZnO/GO were tested against bacteria - Escherichia coli (E. coli). The test results reveal that the antibacterial activity at low loading of the ZnO/GO nanocomposite was higher than that of GO on E. coli.
Keywords: zinc oxide; graphene oxide; nanocomposite; antibacterial; E. coli.
Synthesis of Ag nano/TiO2 by γ-irradiation and optimisation of photocatalytic degradation of Rhodamine B
by Vo Thi Thu Nhu, Huynh Nguyen Anh Tuan, Nguyen Quoc Hien, Do Quang Minh
Abstract: The effect of Ag nano content in Ag nano/TiO2 materials was studied with regard to the photocatalytic degradation of Rhodamine B (RB) as a model pollutant from textile industry. Ag nano/TiO2 materials were prepared by γ-irradiation method and characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis and surface area measurement by Brunauer-Emmett-Teller (BET) method. At 1.5% Ag content, the Ag nano/TiO2 photocatalyst exhibited the highest visible light photocatalytic activity. Several influence factors of the RB degradation process such as the content of catalyst, the initial concentration of dye, the irradiation time and pH of the reaction mixture were also investigated. Design Expert software version 7 was used to optimise the effects of the experimental parameters on the responses. The results of experiments were fitted to two quadratic polynomial models developed using response surface methodology (RSM). The results showed that the predicted data from RSM are in good agreement with the experimental results with a correlation coefficient (R2) of 0.9915. The maximum degradation efficiency (82.61%) was achieved at initial RB concentration: 10-5 M, catalyst dosage: 1.44 g/L, irradiation time: 63.8 min and pH: 6.15.
Keywords: TiO2; Ag nano; γ-irradiation; photocatalytic; degradation; RB; response surface.
Effect of the seed particles and reductants on the formation of nanosized gold colloid
by Nguyen Thi Nhat Hang, Ngo Thi Tuong Vy, Nguyen Canh Minh Thang, Nguyen Thi Phuong Phong
Abstract: In this study, gold nanoparticles (GNPs) with different sizes and shapes were synthesised by seed-mediated method. The nano-seeds were synthesised by the Turkevich method and presented an average diameter of 17.6 nm. Different reducing agents such as hydroquinone (HQ), ethylenediaminetetraacetic acid (EDTA), and protecting agents such as citric acid (CA), trisodium citrate (TSC) were used in the growth solution with different volumes of seeds solution. The morphology and size of the synthesised GNPs were characterised by UV-Vis spectrophotometry, transmission electron microscopy (TEM) and scan electron microscopy (SEM). We obtained colloidal GNPs with diameters ranging from 32.1 nm to 509.2 nm.
Keywords: gold nanoparticles; GNPs; trisodium citrate; TSC; citric acid; ethylenediaminetetraacetic acid; EDTA; size; shape.
Process characterisation of deep reactive ion etching for microfluidic application
by Chien Mau Dang, Ngan Nguyen Le, Khanh Kim Huynh, Hue Cam Thi Phan, Dung My Thi Dang, Eric Fribourg-Blanc
Abstract: The goal of this paper is to investigate the influence of parameters of the Bosch deep reactive ion etching (DRIE) process on etched surface profile, sidewall profile and etch rate of micrometre silicon features. By investigating these parameters, we found the conditions to obtain smooth sidewall, high etch rate and balance of chemical and physical etching in the DRIE process. In this paper, the silicon surface was covered by a thin silver patterning, created by lift-off, as a hard mask for the DRIE process. The etched samples were characterised by optical microscopy and mechanical profilometry. The results show smooth sidewall of 136 μm-deep silicon trenches obtained at a high etch rate of 4 µm/min using 5 sccm C4F8, 8 sccm O2 and 24 W of bias power.
Keywords: deep reactive ion etching; DRIE; vertical sidewall; surface profile; microfluidic.
3D laser lithographic fabrication of hollow microneedle mimicking mosquitos and its characterisation
by Masato Suzuki, Tomokazu Takahashi, Seiji Aoyagi
Abstract: Microneedles mimicking mosquitos were fabricated by employing a three-dimensional laser lithography. An ultra-precision three-dimensional laser lithography system 'Nanoscribe GT' is employed. On the basis of two-photon absorption phenomenon, an extremely small space of less than 200 nm in the photocurable polymer material is cross-linked, where a laser beam is focused. The total cross-linked space finally emerges after development process. First a bundled needle comprising three parts was fabricated, which imitates central hollow labrum of sucking blood, and two side solid maxillae having jagged edges. Second, a practical needle comprising two parts was proposed and fabricated. The functions of three-piece mosquito's proboscis (one labrum and two maxillae) are integrated to two parts. Each half-needle has semi-circular channel and jagged edges. By combining the two-halves, one hollow microneedle is realised. Alternative motion like mosquito maxillae is possible. Fluid is introduced into the channel through small holes in the wall, and is drawn up by capillary force. Reduction in number of microneedles simplifies both fabrication process and drive system for puncturing. It was experimentally confirmed that the needle successfully penetrates PDMS skin. The effectiveness of alternative motion of two parts with 90° phase to each other was also investigated.
Keywords: microfabrication; three-dimensional fabrication; rapid prototyping; microneedle; low invasive treatment; stiffness test; insertion test; blood sampling test.
Thermosensitive heparin-Pluronic copolymer as effective dual anticancer drugs delivery system for combination cancer therapy
by Nhat-Anh N. Tong, Ngoc Quyen Tran, Xuan Thi Diem Trinh Nguyen, Van Du Cao, Thi Phuong Nguyen, Cuu Khoa Nguyen
Abstract: In recent years, cancer therapy regimens combining dual drugs have proved their effectiveness in comparison with single drug. To increase efficacy of these anticancer drugs, an emerging approach involving the development of nanocarriers for dual anticancer drugs delivery has recently received much attention. In the study, thermosensitive Pluronic®-conjugated heparin was prepared to encapsulate and control the delivery of aquated cisplatin (CDDP) and 5-fluorouracil (5-FU) chemotherapeutic agents. The drug delivery system was determined to be in the size range of 80-100 nm by TEM and 260 nm by DLS. Formation of the complex was confirmed by 1H-NMR and FT-IR. The nanocomplexes exhibited high drug loading capacity (approximately 9.01% wt/wt of CDDP and 88.24% wt/wt of 5-FU). In vitro, drug-loaded nanogels showed slow and sustained release of the drugs over a long period of time at physiological pH and body temperature. Moreover, the cytotoxicity assay results also indicated that Hep-F127 was cytocompatible. Meanwhile, CDDP-5FU-Hep-F127 nanocomplexes show a significantly inhibited NCI-H460 lung cancer cell growth with the IC50 1.23 ± 0.07 µg/mL. The in vitro preliminary results indicate that the Hep-F127 nanocomplex is a candidate for suitable CDDP and 5-FU delivery which can be studied further in cancer therapy.
Keywords: thermosensitive nanogels; combination cancer therapy; delivery of dual anticancer drugs; cisplatin (CDDP); 5-fluorouracil (5-FU).
Polymeric chitosan based nanogels as a potential platform for dual targeted drug delivery in cancer therapy
by Tuong Vi Tran, Thanh Hien Dang Phuong, Ngoc Quyen Tran, Cuu Khoa Nguyen, Dai Hai Nguyen
Abstract: Dual-drug delivery system (DDDS) is reported as an outstanding candidate for the treatment of cancer. In this study, self-assembled nanogels were fabricated using poly (ethylene glycol) methyl ether (mPEG) and chitosan for a combination of drugs, paclitaxel (PTX) and 5-fluorouracil (5-FU). Especially, variable mPEG molar concentrations were prepared for the purpose of improving the water solubility of chitosan, creating new opportunities for DDDS. The chemical structure of mPEG-chitosan copolymer was determined by proton nuclear magnetic resonance (1HNMR) and Fourier transform infrared spectroscopy (FT-IR). The combined drugs loaded nanogels were spherical in shape, which was revealed by transmission electron microscopy (TEM). In addition, the entrapment efficiencies of PTX and 5-FU were around 50% and 10%, respectively. The release profiles of either PTX or 5-FU exhibited considerable association with favourable hydrophilicity of mPEG. Overall, these results demonstrated that mPEG-chitosan nanogels present potential for controlled release of PTX-5-FU working as a delivery system in cancer therapy.
Keywords: dual-drug delivery; poly (ethylene glycol) methyl ether; chitosan; paclitaxel; 5-fluorouracil.
Improving gold nanowire-based biosensor sensitivity by changing probe designLinh
by Cao Huu Tien, Ha Van Linh, Pham Xuan Thanh Tung, Le Van Hieu
Abstract: To improve the sensitivity of the electrochemical DNA (E-DNA) sensors is extremely necessary for the diagnosis and early detection of cancer. Among the factors that affect the sensitivity of the sensors, the most important is the structure of the probe on the electrode surface. Probes may have different structures, but have only two detection mechanisms, that is signal-off and signal-on. Many reports suggest that the detection effect of signal-on probe is better than signal-off probe. To verify this, we have conducted experiments on two probes that have similar sequences which are complementary with target and typical for two detection mechanisms of the sensor, i.e., probe has stem-loop structure according to the signal-off mechanism, and probe has hairpin structure according to the signal-on mechanism in the same experimental conditions. The results showed that the limit of detection (LOD) of sensor with stem-loop probe is 200pM, meanwhile hairpin probe sensor has LOD of 25 pM.
Keywords: E-DNA sensor; stem-loop probe; hairpin probe; interleukin-8 mRNA; oral cancer.
Application of silicon nanowire for detection and quantitative analysis of alpha-fetoprotein biomarker
by Van Binh Pham, Thi Thanh Tuyen Le, Thanh Nhat Khoa Phan, Tien Thang Nguyen, Chien Mau Dang
Abstract: Semiconductor silicon nanowires (SiNWs) have shown great potential in detection and quantitative analysis of human disease biomarkers. Compared to current methods such as fluorescence diagnosis, enzyme linked immunosorbent assays (ELISA) or western blot, the label-free technique using SiNWs as sensors allows fast, efficient and inexpensive detection and quantification of biomarkers. In this research, SiNWs surfaces were modified by antibody of alpha-fetoprotein (AFP), a well-known biomarker of liver cancer. This antibody was immobilised to facilitate the specific capture of AFP. The efficiencies of surface modification and antibody immobilisation were estimated by contact angle measurement, fluorescence microscopy, chromogenic reaction, ultraviolet-visible (UV-Vis) spectroscopy and electrical characterisation of the SiNWs after every surface modification step. A calibration curve between AFP concentration and SiNWs' electrical response was built, from which any other sample with arbitrary concentration of AFP can be quantitatively diagnosed with the SiNWs.
Keywords: biosensor; silicon nanowire; SiNW; alpha-fetoprotein; AFP; liver cancer; fluorescence.
A versatile approach to synthesise optically active hierarchical ZnS/ZnO heterostructures
by Do Quang Trung, Nguyen Tu, Pham Toan Thang, Pham Thanh Huy
Abstract: One-dimensional hierarchical ZnS/ZnO heterostructures have been successfully fabricated by combining thermal evaporation method and in-situ/post oxidation process. Various morphologies of the secondary ZnO nanostructures such as nanosheets, nanoparticles, and nanoteeths were found to form on the ZnS nanowire backbone. The optical properties of the heterostructures were investigated by high-spatial resolution cathodoluminescence spectroscopy. It was demonstrated that optically active hierarchical ZnS/ZnO heterostructures, which strongly emit UV light with two emission bands at around 335 nm and 380 nm characterising both the ZnS and the ZnO phases, can be realised by controlling the oxidation temperature and duration. This research introduces a simple route to synthesise optically active ZnS/ZnO heterostructures.
Keywords: ZnS/ZnO heterostructures; one dimensional nanostructures; optical properties; thermal evaporation method; in-situ oxidation; post oxidation; ZnS-ZnS phase transition.