We have developed a new method to pattern polymeric materials, including non-thermoplastic polymers, at low
temperature and low pressure. In this method, plasticizers are added to increase the chain mobility of the polymers,
resulting in lower imprinting temperature and/or pressure. Two established imprinting and transfer techniques were
chosen to demonstrate this method, namely, conventional nanoimprint lithography (NIL) and microcontact printing
(μCP). These two techniques were used to pattern poly(3,4-ethylenedioxythiophene) (PEDOT). PEDOT was chosen
because it is a non-thermoplastic polymer and therefore cannot be easily patterned using conventional NIL. Successful
imprint of PEDOT films from the PDMS mold was achieved at a low pressure of 10 kPa and 25°C by controlled
addition of glycerol as a plasticizer using conventional NIL; well-defined arrays of 2μm wide, 185 nm high PEDOT
dots have also been demonstrated by μCP. In contrast, patterning of PEDOT film without plasticizer requires higher
temperature (80°C) and pressure (10 MPa), which could cause severe deformation of the transferred patterns. This
method of plasticizer-assisted imprint lithography (PAIL) broadens the applicapability of NIL to a wide range of
For effective pulmonary drug delivery of insulin for example, drug particles must be in the range of 1 to 5 microns. A piezoelectrically actuated MEMS atomizer based on Rayleigh instability-driven breakup of filaments has been designed to produce drug particles in this range. Although the formation of droplets from jets have been used extensively in ink-jet printing, the currently presented mode of droplet formation has not yet been demonstrated by any MEMS device. Testing of the vaporiser reveals that the droplets generated lie primarily in the range of 1.0 through 3.0 microns, a range that covers the designed droplet size of 2.5 microns. We thus show that it is possible to implement this mode of droplet generation that will achieve better device efficiency.
This paper reports a process used for the microfabrication of an array of hollow microneedles. The purpose of the array is for painless transdermal drug delivery. The fabrication process uses wet bulk silicon technology and copper electroplating technology. First, a microneedle array mold on <100>-oriented silicon was fabricated by wet anisotropic etching using KOH solution, then the silicon mold was electroplated with copper. After which, the hollow copper microneedle array was released by a lift-off process or by etching off the silicon mold in KOH solution. The hollow copper microneedle array has been mounted on a polycarbonate platform, which consist of laser ablated cavities and channel for external connection to drug source. In consideration of the contour of human’s skin and the geometry of the microneedle tip, which has walls of sloping gradient corresponding to the (111)-planes, the height of the microneedle array is 200 μm. Two arrays of hollow copper microneedle were fabricated. They have square base of dimensions 390 μm and 400 μm and square tips of size 100 μm and 120 μm with square holes of size 88 μm and 94 μm respectively. Both arrays have microneedle tips at 1900 μm apart from one another and consist of 10 × 10 microneedle tips.
A methodology for the simulation of a reciprocating displacement micro-pump is presented. First a check valve model was analyzed using coupled FEM to obtain the characteristics relationship between flow rate and the pressure as well as the minimum valve opening pressure. Then a model for the micro-pump actuator driven by PZT disks is proposed and simulated. The pump model takes into account the effects of chamber pressure and geometrical parameters. The maximum downward deflection of the actuating membrane is taken as the target parameter to analyze. It was found that the maximum membrane deflection could reach over 10micrometers microns, much larger than the radial displacement. This 'displacement amplification' is the underlying working principle of this kind of micro-pump. Quantitative analyses of the effects of various factors on the deflection are conducted. It is found that the thickness of the membrane has the biggest influence on the deflection. For each membrane thickness, there exists an op[t9kum PZT disk thickness that gives the maximum deflection at a particular electric field. Other factors with less influence on the deflection are also investigated. An optimum set of design parameters for the micro-pump is obtained form the analyses.
A 3D model of one type of micro pumps was supposed and analyzed using finite element method (FEM). The pump had square shape cavity and was driven by a square shape PZT component. The finite element analysis (FEA) took into consideration of the effects of PZT component dimensions, membrane thickness, pump chamber pressure and other geometric parameters. Modal analyses were also conducted. Compression ratio of the pump chamber was taken as the prime parameter for the analyses. It was found that the membrane thickness and the PZT plate thickness played major roles in determining the compression ratio. For each membrane thickness, there was always an optimum PZT plate thickness that gave the maximum compression ratio. Curves showing the relationship between the optimum PZT plate thickness and the membrane thickness at different chamber pressures were given, based on the FEA results. A set of optimum pump design parameters was proposed.
In this paper, the feasibility of a self-oscillating anemometer is examined. A 2D numerical study of a novel self-oscillating anemometer that can be fabricated using micromachining techniques is performed. The device is essentially a square cylinder suspended in the fluid flow by a fixed beam. The flow velocity can be easily measured by determining the frequency of oscillation obtained from capacitance sensing. Anemometer with different length scales can be fabricated to enable different ranges of velocities to be measured.
In this paper, simulation studies to determine the feasibility of producing filaments using `drop and demand' techniques are presented. These filaments will break up into droplets due to the phenomena caused by Rayleigh instability. In the biomedical applications, for effective pulmonary drug delivery of insulin, for example, the drug particles must be in the range of 1 to 5 microns in size. This stringent requirement is also encountered in gas flow seeding for Laser Doppler Velocimetry studies. A piezoelectrically actuated MEMS atomizer based on Rayleigh instability-driven break-up of filaments has been designed to meet this requirement. Although the formation of droplets from jets has been used extensively in ink-jet printing, the currently presented mode of droplet formulation has yet to be demonstrated in a MEMS device.