Ricky Tjeung

Monash University (Australia)

We present a device capable of combining nanofluidics and cryogenic transmission electron microscopy (cryo-TEM) to allow inspection of water-soluble samples under near-native conditions. The devices can be produced in a multitude of designs, but as a general rule, they consist of channels or chambers enclosed between two electron-transparent silico...

We report on the experimental realization of propagation-based x-ray microscopy with laboratory sources equipped with waveguides. We discuss about the experimental setup, the fabrication steps, and the characterization procedures of the waveguide optics. We demonstrate that the system enables high resolution attenuation imaging of poorly absorbing...

Compared with preformed anisotropic matrices, an anisotropic matrix that allows users to alter its properties and structure in situ after synthesis offers the important advantage of being able to mimic dynamic in vivo microenvironments, such as in tissues undergoing morphogenesis or in wounds undergoing tissue repair. In this study, porous gradient...

Many cellular characteristics such as cell attachment, migration, morphology and proliferation are affected by porosity and pore size of bioactive gradients. Therefore, engineering a gradient that mimics the porosity relevant features of different living tissues can provide a better understanding for some of these cellular characteristics. In this...

We have developed a new porous gradient microfluidic device based on in situ Gtn-HPA/CMC-Tyr hydrogel that comprises gelatin hydroxyphenylpropionic acid (Gtn-HPA) conjugate and carboxymethyl cellulose tyramine (CMC-Tyr) conjugate. The device is fabricated using a soft lithographic technique, in which microstructures were patterned on a thin layer o...

A surface acoustic wave (SAW) actuated rotary motor is reported here, consisting of a millimeter-sized spherical metal rotor placed on the surface of a lead zirconate titanate piezoelectric substrate upon which the SAW is made to propagate. At the design frequency of 3.2MHz and with a fixed preload of 41.1 mu N, the maximum rotational speed and tor...

Treatment of surfaces to change the interaction of fluids with them is a critical step in constructing useful microfluidics devices, especially those used in biological applications. Silanization, the generic term applied to the formation of organosilane monolayers on substrates, is both widely reported in the literature and troublesome in actual a...

The microfluidic applications of a ZnO/Sapphire based layered surface acoustic wave structure are being investigated. Properties of the ZnO/Sapphire layered SAW device including surface wave velocity and propagation loss were measured and correlated to the fluidic behavior of micro droplets. Acoustic streaming was observed in the form of two vortic...

We present a surface acoustic wave (SAW) actuated rotating micro motor. The rotors are 1 millimeter metal spheres which are placed on the surface of a Lead Zirconate Titanate (PZT) substrate with IDTs designed to generate SAW with ~ 700 m wavelength. A Laser Doppler Vibrometer (LDV) was used to visualize the travelling SAW and the result was compar...

We present a method for controlling the motion of microparticles suspended in an aqueous solution, which fills in a microchannel fabricated into a piezoelectric substrate, using propagating surface acoustic waves. The cross-sectional shape of this microchannel is trapezoidal, preventing the formation of acoustic standing waves across the channel wi...

Laser markings are widely used for identification and traceability. With the miniaturization of semiconductor devices, material removal in conventional deep laser markings is undesirable as it could cause contamination. Shallow laser markings 1–6 µm in depth could be produced by melting and reshaping the material, with virtually no material removal...

Microstructures were formed on low temperature co-fired ceramic (LTCC) green substrates with high fidelity using micro embossing. The impact of embossing temperature and pattern density against the embossed profiles was investigated. The increase in pattern density resulted in a macro deformation in addition to embossed micro-depth. The macro defor...

We present a thermally activated solvent bonding technique for the formation of embedded microstructures in polymer. It is based on the temperature dependent solubility of polymer in a liquid that is not a solvent at room temperature. With thermal activation, the liquid is transformed into a solvent of the polymer, creating a bonding capability thr...

We present a thermal activated solvent bonding technique for the formation of embedded microstrucutres in polymer. It is based on the temperature dependent solubility of polymer in a liquid that is not a solvent at room temperature. With thermal activation, the liquid is transformed into a solvent of the polymer, creating a bonding capability throu...

Low Temperature Co-fired Ceramic (LTCC) is expected to be widely used as multi-functional substrate for electronic circuit boards and platforms of microsystems. Miniaturised structures such as micro cavities and vias are conventionally formed by mechanical punching or laser machining. These methods, however, encounter difficulties in machining comp...

We introduce a novel adaptation of the solvent bonding of polymer substrates to create embedded microchannels for application in the fabrication of microfluidic devices. The technique involves the use of a thermally activated solvent and the displacement of solvent in the microchannel. A typical process time is 5 to 10 minutes and high strength sea...

We report on the development of some process capabilities for a polymer-based, multi-layer microelectrofluidic platform, namely : the hot embossing process, metallization on polymer and polymer bonding. Hot embossing experiments were conducted to look at the effects of load applied, embossing temperature and embossing time on the fidelity of line a...

We report on recent advances in micro fabrication technology using micromoulding and high-aspect ratio structuring of photopolymer. The direct application is the realization of components for millimeter-size, ultrasonic piezoelectric motors. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demo...

Micro hot embossing experiments were conducted on polymethyl methacrylate (PMMA) to look at the effects of holding load, temperature and time on the fidelity of line arrays representing micro channels. The results revealed that the holding temperature was a more sensitive parameter than the others due to its large effect on the polymer's viscoelast...

We report on the development of a low cost, manufacturing process for a threedimensional network, microelectrofluidic platform. The platform consists of multiple levels of fluidic channels and electrical circuits. The inter-level channels and circuits are connected through via holes and conductor-filled via holes respectively. The medium surroundin...

"Supervisor, Associate Professor Christopher Shearwood." Thesis (M.Eng.) -Nanyang Technological University, School of Mechanical and Aerospace Engineering, 2005.