Micropump system

A number of patented technologies for multiparticulate dosage forms have been described recently, such as the Micropump system, which is an osmotically driven coated microparticle system designed to increase the absorption time for rapidly absorbed drugs.59 Combination of water-soluble and water-insoluble polymers could provide enhanced controlled release rates and profiles. A patented technology (COSRx) has been reported to be capable of delivering various sophisticated release profiles. The formulation involves a guar-gum-based tablet and a combination of water-soluble and water-insoluble polymeric tablet coat.60... 

Magnetic Pumps, Fig. 2 (a) Schematic and (b) photograph of micropump system of [4] (Reprinted from [4] with permission from Dr. Yamahata)... 

Matteucci M, Pta-ennes F, Marmiroli B, Miotti P, Vaccari L, Gosparini A, Turchet A, Di Fabrizio E (2006) Compact micropumping system based on LIGA fabricated microparts. Microelectr Eng 83(4-9) 1288-1290... 

The reaction of ammonia with OPA in the presence of 2-mercaptoethanol is the basis of a simple, economic and transportable analyzer system for shipboard monitoring (Figure 7.36). The method makes use of a solenoid micropump system applying a reverse FIA concept, i.e. the reagent is injected into the sample flow, which is consequently also used as carrier. A specially made detection cell for fluorescence detection of the reaction product isoindol-l-sulfonat is made and combined with a commercial photomultiplier tube, a long-pass optical filter, and an UV-LED as excitation light source. An LOD of 13 nmol/1 is achieved [121]. 

Modeling of electrokinetic micropump systems has predicted that the additive, i.e., trimethylammoniopropane sulfonate, cf. Figure 2.2, will result in up to a 3.3-fold increase in the pumping efficiency and up to a 2.5-fold increase in the generated pressure. The predicted values agreed well with the experimental results for flow, pressure and efficiency. Using this additive, pressures up to 156 kPa V and an efficiency up to 5.6% could be reached. 

Figure 7.16 shows the schematic of an MHD micropumping system for a microchannel of length, L height, H and width, W. A planar electrode of length, and height, H, is placed on... 

Microfabricated systems. Based on the characteristics, microfabricated systems include microchips and micropumps. 

Silicon micropumps offer major advantages in terms of system miniaturization and control over low flow rates with a stroke volume 160 nL.14 The micropump has the characteristics of very small in size, implantability in the human body, low flow rates (in the range of 10 pL/min), moderate pressure generation from the microactuator to move the drug, biocompatibility, and most important, a reliable design for safe operation. The implantable device is particularly suitable (over the injectable drug delivery systems) for patients with Parkinson s disease, Alzhiemer s disease, diabetes, and cancer, as well as chronically ill patients, because the catheter that is attached to the device can transport drug to the required site. 

As described earlier, the basic design of the micropump involves a drug reservoir attached to a pumping device with or without a sensor. The inclusion of a sensor with the device makes it a closed-loop system, where the device can check the levels of marker molecules such as glucose and deliver the therapeutic agent. In many systems the devices are implanted such that the reservoir can be charged when it is exhausted. The device may pump at a basal rate or may be controlled by a circuit connected in a closed loop with a sensor or by a handheld remote control device by the patient. 

Maillefer, D., Rey-Mermet, G., Hirschi, R. A high-performance silicon micropump for an implantable drug delivery system. 12th IEEE MEMS 1999, Technical Digest, Orlando, FL, 1999. 

Initially, the main goal of miniaturization was to enhance the analytical performance of devices rather than to reduce their size. However, it was found that such tools had the advantage of reducing the consumption of sample and reagents, for example, the smaller consumption of carrier and mobile phases in separation systems (the first analytical system to be miniaturized was the gas chromatograph). Research in this area focused on the development of components such as micropumps, microvalves, and chemical sensors. 

Because of the enormous diversity in components it is difficult to describe a straightforward design-path for components for the MCB concept. Here we focus on the modeling and the design of the fluid control modules and specific on the thermo-pneumatic actuated micropump used (twice) in the demonstrator. An elaborated model of this micropump is given by van de Pol et al. [21]. The main functions of the fluid control in micro analysis systems are the switching function and the direct flow and/or pressure control. Building blocks are hydraulic inertances, resistors, capacitors and passive and control-valves. Very often an active element like a micropump is needed. 

The demonstrator analyzing system contains two thermo-pneumatic actuated micropumps (see Fig. 7). The micropumps are of the reciprocating type and consist of three main building blocks a thermo pneumatic actuator (A), a pump chamber with a flexible pump membrane which acts as a capacitor (C) and two passive circular silicon check valves (V), see Fig. 21. 

Several techniques for miniaturization of simple chemical and medical analysis systems are described. Miniaturization of total analysis systems realizes a small sample volume, a fast response and reduction of reagents. These features are useful in chemical and medical analysis. During the last decade many micro flow control devices, as well as the micro chemical sensors fabricated by three dimensional microfabrication technologies based on photofabrication, termed micromachining, have been developed. Miniaturized total analysis systems (pTAS) have been studied and some prototypes developed. In microfabricated systems, microfluidics , which represent the behavior of fluids in small sized channels, are considered and are very important in the design of micro elements used in pTAS. In this chapter microfluidics applied flow devices, micro flow control devices of active and passive microvalves, mechanical and non-mechanical micropumps and micro flow sensors fabricated by micromachining are reviewed. 

Keywords Microfluidics, micro total analysis system (pTAS), microvalve, micropump, micro flow sensor. 

Disposable pTAS will be ideal for medical use [14]. However, the high fabrication cost of sophisticated pTAS including micropumps and microvalves is a real problem. One of the basic components of medical pTAS taking this into account is illustrated in Fig. 2. A detector cell consists of micro sensors and a 3-way microvalve is placed at the sample inlet. Flow is controlled by a suction pump and an injection pump connected to the detector cell. The calibration solution flow is also controlled by an individual pump and a 3-way valve. In this system, only sample flow reaches the detector cell. The upper parts of the system are free from contamination and corrosion so that they can be reused many times, while the detector cell has to be disposed of. To realize this system, a 3-way microvalve which can handle whole blood is indispensable. A separable channel type microvalve whose channel part is disposable while actuator part is reusable is useful for the 3-way microvalve of the detector cell [15]. Mechanically fixed stack structures including disposable parts are useful in many medical pTAS. 

The characteristics of the actuators, check valves and micropumps which have been used in flow systems are listed in Table 3, Table 4, and Table 5 respectively. The characteristics depend on the dimensions designed so that these are only typical values. 

ISFET based systems have been developed at different laboratories [91 -93] using a planar or three dimensional set up. Such systems which are equipped with micropumps and valves are able to detect ions and other interesting chemical parameters (Fig. 4). Different approaches have been made in the detection of ions and diluted gases. Microarrays for measuring pressure, temperature, pH, 02 and C02 were realized using silicon technology and a hybrid set up of the different components [94]. Blood gas measurements with integrated pH, 02 and C02-electrodes have been tested in real samples [95]. 

Microreactor technology has developed to such an extent that a wide variety of microreactor components, e.g. micropumps, mixers, reaction chambers, heat exchangers, separators and complete integrated microreaction systems with process control units have been fabricated using the appropriate microfabrication process and materials that are suitable for specific applications. 

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