This paper presents a novel, high sensitive and miniaturized fluorescence detection system which integrated a LED
light source, all necessary optical components and a photodiode with preamplifier into one package about 2 cm x 2 cm x
2 cm especially for the applications of lab-on-a-chip, portable bio-detection system and point-of-care diagnostic system.
The prototype has been tested using the fluorescence dye 5-Carboxyfluorescein (5-FAM) dissolved into solvent DMSO
(Dimethyl Sulfoxide) and diluted with DI water as the testing solution samples. Resolution approximation method is
accepted to evaluate the sensitivity. The testing results prove a remarkable sensitivity at pico-scale molar, around 1.08
pM/L, which should meet the most of bio-detection requirements. This cost-effective detection system can be widely
integrated to the portable device and system for fluorescent detection in biological, chemical, medical, point-of-care
An enzyme based biosensor was fabricated by employing a simple, inexpensive and rapid xurography fabrication
process. The electrodes and channel were made from the conducting polymer poly(3,4-ethyelenedioxythiphene)
poly(styrene sulfonate) (PEDOT:PSS). PEDOT:PSS was selectively deposited using a polyimide tape mask. The tape
mask was peeled off from the substrate after annealing the polymer in vacuum. Polymer wells of defined dimensions
were made and were attached to the device to accommodate the solutions. This sensor utilizes the change in current as a
parameter to measure different analyte concentrations. Initial experiments were done by using the sensor for glucose
detection. The sensor is able to detect the glucose concentrations approximately from 1 μM to 10 mM range covering
glucose in human saliva (8-210 μM). The glucose oxidase activity was independently measured using colorimetric
method and the results indicate that the sensor retains the enzyme activity and can be used as a biosensor to detect
various analytes. The analyte of interest can be measured by preloading the corresponding enzyme into the wells.
The principle, experiment setup and experimental results of a novel process of controlling the nanoparticle distribution in hydrogel by utilizing the theory of electrophoresis are discussed and demonstrated. The distributed nanoparticles in hydrogel changed the refractive index of the material, which provide the new application for organic gradient refractive index (GRIN) lens. For conducting the electrophoresis experiments, two miniaturized electrophoresis running tools have been designed and fabricated. The dimensions of vertical ruing tool is about 4 x 3 x 3.5 cm (L x W x H). In order to clearly observe the running results, the process of self-assembly are used to label the nanoparticles with fluorescent dye. The silica nanoparticles (7-9 nm in diameter) are being investigated to explore its effect on the optical improvement of hydrogel material. Polyacrylamide hydrogel is used as lens material. Various analysis equipments are employed to characterize the samples, including X-ray photoelectron spectroscopy (XPS), thin film measurement system and fluorescent microscopy. The experimental results from fluorescent microscope have shown that nanoparticles were moving toward the opposite charged electrode from particle resource and distributed according to the electrical field. For GRIN lens application, the electrophoresis phenomena have also been investigated by the testing setup with a circular electrode (3 cm in diameter). The testing results were examined by thin film measurement system and X-ray photoelectron spectroscopy. With the data of analyzed Si concentration, it has been proven again that the distribution of nanoparticles could be controlled by electrophoresis in hydrogel film which presents the radial gradient refractive index profiles. The refractive indices change range could be larger than 0.06. The simulation results with CoventorWare@ also predicted the nanoparticles movement and distribution in hydrogel under electrical filed with different values of electrophoretic mobilities.
A novel process of casting the polydimethyl-siloxane (PDMS) microstructure with hybrid photoresists mold has been developed to fabricate the 3D microstructure. This new processing includes two parts: the 3D mother mold fabrication and PDMS casting processing. The 3D mother mold, which consists of the three-dimensional partial-spherical microstructure and micro channel, was successfully fabricated and characterized. The 3D micro structure and the micro channel of the mother mold, made of two different photosensitive materials, AZ100XT and SU8 photoresist respectively, are merged very smoothly at the joint area. A mother mold of a 2200-μm-diameter chamber with a 500-μm-width channel was presented in this paper. For the best precise dimensional control, we used this mother mold to fabricate the PDMS mold for PDMS casting processing. The surface average roughness of the final 3D structure is 30 nm. This novel processing provides a new technology for achieving smooth 3D chamber surface joined with microchannel. This new technology can be applied in various lab-on-a-chip and microfluidic devices such as micropump and microvalve for which the great sealing, no dead volume and high back pressure are critical requirements. In this paper, the design, fabrication process and surface profile characterizations of this processing are presented in details.
The hard magnetic materials with a high remnant magnetic moment, Mr, have the unique advantages that can achieve bi-directional (push-pull) movement in an external magnetic field. This paper presents the results on fabrication and testing of the novel hard magnetic silicone elastomer thin films. The micro-size hard ferrite powder, NdFeB powder and different silicone elastomers have been used to fabricate the various large elongation hard magnetic thin films. The uniform thin films range from 40 μm to 216 μm and they are successfully fabricated. Three different fabrication processing have been investigated and the mechanical properties, like Young’s modulus and deflection force, have been evaluated. The simulation results with ANSYS match the experimental data. In comparison to electrostatic or piezoelectric actuation, the magnetic actuation can provide stronger forces and larger deflections. The large elongation hard magnetic thin film provides an excellent diaphragm material, which plays an important role in the micro pump or valve. This film movement has been tested in the external magnetic field, and proved to have large deflections and high performances.
Novel highly integrated microreactors have been fabricated on silicon in order to dehydrogenate cyclohexane to benzene. There are 12 reactor chips on one single silicon wafer. The microreactor consists of three layers, which are reaction chamber integrated with heaters and thermal sensors, separation layer integrated with cantilever flowmeters and gas cover.
An experimental system has been designed and constructed to conduct gas- solid heterogeneous catalytic reactions in microreactors. This apparatus is inteded to be used for any exothermic or endothermic reaction, including those with multiple feeds. It can be used to test the effectiveness of a microreactor design for a particular catalyst or to test the behavior of the catalyst itself. The system uses a test block that is plumbed for multiple feeds and vacuum to hold down a standard size microreactor chip. This chip has two exit vias, which includes one for the reactor effluent and one for the exit stream from a possible reactor membrane wall. The reactors are systems of channels with a smallest cross-dimension as small as 5 micrometers. The experimental system is equipped with temperature control and automatic data acquisition. The reactors can be stacked in order to scale up to higher throughput. A simulator has been developed that accounts for the unique physical aspects of reaction and flow in very small channels. Along with design, it assist in determining operating conditions and interpreting experimental results.
A series of millimeter-sized, addressable linear and rotary surface-driven electrostatic positioners are currently being designed and fabricated. The major components of these positioners are a thin copper-coated glass epoxy stator board and a carbon-coated polymer film slider which is placed on top of the stator board. Using modified Printed Circuit Board technique, a group of conductive electrodes are linearly or radially arranged on the stator board. On application of an excitation voltage pattern to the stator electrodes, a mirror image of the stator electrical charges will be induced on the film slider. Sequential switching of the voltage pattern will lead to electrical charge interactions, resulting in continuous motion of the film slider. Compared to the electromagnetic counterparts, these electrostatics-based positioners do not require the conventional mechanical assembly of transmission gears and rails for operation, thus are compact in design and light in weight. The potential advantage of low manufacturing cost may help this new type of positioners find a wide range of industrial, military, and commercial applications.