Micropumps for drug delivery

Microactuators, Fig. 4 In-plane micropump for drug delivery composed of diffuser, nozzle, pumping chamber, and electrothermal microactuator (Image courtesy of Texas Microfactory Lab, ARRI-UTA)... 

Disposable Micropumps for Drug Delivery. Disposable micropumps manufactured by Acuros in Germany are capable of delivering a preset amount of liquid hormones, proteins, antibodies, or other medications. An osmotic microactuator, based on osmotic pressure, is used to regulate the amount of drug delivered, and there are no moving parts or power supply components. 

Bourouina T, Bosseboeuf A, Grandchamp JP (1997) Design and simulation of an electrostatic micropump for drug-delivery applications. J Micromechan Microengin 7 186-188... 

Both miniaturized analyte sensors and microsystems for drug delivery have been demonstrated, and the integration of both functionalities within one medical device is the next natural step. Smart polymer-based sensors, actuators, microvalves, micropumps, etc., can be combined in a single microfluidic system to construct medical devices with applications in diagnostics and/or treatment, and first attempts at developing such LOC devices are currently underway. 

Zahn, J.D., et al. 2004. Continuous on-chip micropumping for microneedle enhanced drug delivery. Biomed Microdevices 6 183. 

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. 

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. 

One of the earliest types of rotary micropumps developed for microfluidics applications, drug delivery in particular, is the jet-type magnetically driven fluid micropump. It is based on a rotary micromotor which is attached to a toothed rotor (Fig. 1). Basically, it is a micro version of conventional positive displacement pump. Flow rates up to 24 pL/min at a pressure of 10 kPa have been obtained using this design [4]. 

The use of shmuli-responsive polyelectrolytes as conshtuents of thinfilms on mi-crocapsules leads to the production of responsive microcontainers that may be used for controlled drug delivery, or as micropumps, sensors, and actuators. The stimuli-responsive capsules, which contain sensitive polymers either as shell constituents or in their interior, are the subject of an intensively growing area of interest... 

Implanted micropump Limitation on volume of divice only for highly active compounds exclusively for release in liquid from (difficulties in releasing polypeptides due to their low stability in aqueous medium) Local and more economical drug delivery more preferable than parenteral drug administration possibility of pulse and more complex kinetic profile of drug release ... 

The controlled-release micropump (Figure 2) is a recently invented device that uses the principles of membrane transport and controlled release of drugs to deliver insulin at variable rates (20,26). With a suitable supply of insulin connected to the pump, the concentration and/or pressure difference across the membrane results in diffusion or bulk transport through the membrane ). This process is the basal delivery and requires no external power source. Augmented delivery is achieved by repeated compression of the foam membrane by the coated mild-steel piston. The piston is the core of the solenoid, and compression is effected when current is applied to the solenoid coil. Interruption of the current causes the membrane to relax, drawing more drug into the membrane in preparation for the next compression cycle. 

---