We present a novel self-aligned and hybrid polymer fabrication process for an electro-enzymatic glucose sensor. The
self-aligned fabrication process is performed using polydimethylsiloxane (PDMS) as a process substrate material, SU-8
as a sensor structural material, and gold as an electrode material. PDMS has many advantages as a process substrate over
conventional substrates such as bare silicon or glass. During the fabrication process, SU-8 has good adhesion to the
PDMS. However, after completion of all fabrication steps, the SU-8 based sensors can be easily peeled-off from the
PDMS. The PDMS is prepared on a glass handle wafer, and is reusable for many process cycles. Such an SU-8 release
technique from a PDMS substrate has never been proposed before. The novel process is employed to realize a glucose
sensor with active and reference gold electrodes that are sandwiched between two SU-8 layers with contact pad openings
and the active area opening to the top SU-8 layer. The enzyme glucose oxidase is immobilized within the confined active
area opening to provide an active electrode sensing surface.
After successful fabrication using the hybrid process, the overall thickness of the sensors is measured between 166.15 μm
and 210.15 μm. The sensor area and the electrode area are 2mm x 3mm and 2mm x 2mm respectively. The resulting
glucose sensors are mechanically flexible. A linear response is observed for the glucose sensors, typically between
50mg/dl and 600mg/dl glucose concentrations.
We have demonstrated a solution-phase approach based on homogeneous nucleation and controlled growth for the synthesis of 1-dimensional nanostructures from a chalcogens such as Se, Te, and Se/Te alloys. These nanostructures include monodispersed nanowires, nanorods, and nanotubes with good dimensional control (lateral dimensions from 10 to 1000 nm, and lengths ranging from a 0.25 to >20 μm). These nanomaterials are ideal components for fabricating devices or composites for photoconductive and piezoelectric applications. In this presentation, we will discuss the mechanisms (as revealed by our SEM and TEM studies) for the formation of these 1-dimensional nanostructures, as well as some preliminary measurements on their properties.
We have demonstrated a variety of solution-phase approaches for the synthesis of dimensionally confined nanostructures of a wide range of materials. These materials include metals (Ag and Au) and semiconductors (Te, Se, and Ag<sub>2</sub>Se) with interesting properties such as high electric, thermal, and ionic conductivities, piezoelectricity, and photoconductivity. Direct and indirect routes for the solution-phase synthesis of 1-dimensional nanostructures are presented. Control over morphology, chemical purity, and crystallinity are well maintained. We show that by using solution-phase methods, it is possible to generate not only high yields of nanowires but also more complex structures such as tubes and co-axial nanocables. These nanostructures are ideal for the study of size-confinement effects on electrical and optical properties, and also as the future interconnects and active components in nanoscale electronic and electromechanical devices.
This paper describes the use of confined self-assembly in organizing monodispersed spherical colloids into face-center-cubic crystalline lattices for photonic crystals applications. Using this method, we were able to conveniently control the thickness, the density and structure of defects, and the orientation of a crystal. Inverse opals of polymers and ceramic materials were also synthesized by templating corresponding precursors against three-dimensional colloidal crystals. As an extension to this method, we also demonstrated the hierarchical self-assembly that involved building blocks with sizes on two different scales, and its application in forming inverse opals.
This paper describes a convenient method for self-assembling monodisperse colloidal spheres into 3D ordered arrays with domain sizes as large as several square-centimeters. These arrays have a cubic-close-packed structure or a face-center- cubic lattice similar to that of a natural opal. Each array exhibits a stop band whose position is mainly determined by the diameter of the colloidal particles. This type of structure can serve as a 3D photonic band-gap crystal, which is potentially useful in controlling the emission and propagation of light. The versatility of the present technique has allowed us to tailor the photonic properties of these arrays of colloidal particles. For example, the maximum attenuation of the photonic band-gap can be modulated by controlling the number of layers along the propagation direction of the light. The position of the mid- gap can be roughly changed by controlling the diameter of the particles and subsequently fine-tuned by sintering the sample at elevated temperatures.