A water-powered micro drug delivery system

A plastic micro drug delivery system has been successfully demonstrated by utilizing the principle of osmosis without any electrical power consumption. The system has an osmotic microactuator (see Su, Lin, and Pisano, J. Microelectromech., vol. 11, pp. 736-7462, Dec. 2002) and a polydimethylsiloxane (PDMS) microfluidic cover compartment consisting of a reservoir, a microfluidic channel and a delivery port. The typical dimension of the microfluidic channel is 1 cm in length with a cross-sectional area of 30×100 μm² to minimize the diffusive drug flow while pressure drop remains moderate. Using oxygen plasma to activate the surfaces of polymers for bonding, the osmotic actuator is bonded with the PDMS cover while liquid drug can be encapsulated during the bonding process. Employing the net water flow induced by osmosis, the prototype drug delivery system has a measured constant delivery rate at 0.2 μL/h for 10 h with an accumulated delivery volume of 2 μL. Both the delivery rate and volume could be altered by changing the design and process parameters for specific drug delivery applications up to a few years. Moreover, the induced osmotic pressure can be as high as 25 MPa to overcome possible blockages caused by cells or tissues during drug delivery operations.