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Background

Microresevoir Theory

Fabrication(1,2)

Microreservoir actuation

Integrated Microchip device

Advantages

References

Advantages of microreservoir system [1]

            The controlled-release microchip has numerous advantages due to its design and small scaled size. In comparison to microfluidic pumps which are limited to delivering liquid solutions, each microchip reservoir can store multiple chemicals that can be in any form: solid, liquid, or gel. Drugs or chemicals, and the presence or absence of polymer matrices or excipients stored within the reservoirs have minute or no effect on the electrochemical behavior of the anode membrane. A wide variety of drugs and chemicals can therefore be delivered without compromising the functionality of the device. Thus, drugs that quickly dissolve when released can produce pulsatile drug delivery, whereas materials that dissolve slowly or diffuse out can provide sustained drug delivery. This allows the release rate of the drug to be modified towards the desired application by modifying the drug or chemical’s dissolution properties.
            Since the drugs are stored within separate reservoirs, the amount of drug released can be determined based on the number of anode membranes given an applied electric potential. Each reservoir within the microchip can be specifically filled with a set amount of drugs at nanoliter volumes. When only certain amounts are desired, an applied potential can be delivered at specific time intervals to specific anode membranes. The high controllability of drug release prevents the likelihood of accidental drug overdose that can occur with conventional drug-delivery vehicles such as pressed tablets. The individual reservoirs and single platform design also allows for complex release patterns. Specific anode membrane materials that corrode at certain applied electric potentials can be selectively chosen to cover certain reservoirs. Thus, different anode membrane materials can be patterned on the device such that each dissolves only when the correct electric potential is applied to that specific membrane.
            No mechanically moving parts exist within the microchip since the delivery of drugs occurs by means of an electrochemical reaction initiated by the application of an electric potential. Without moving parts the longevity of the device is greatly increased. The longevity of drug or chemical life is also increased due to the water impenetrable membrane hermetically sealing reservoirs. This not only prevents interaction with the surrounding environment but also keeps the drug in a stable form. 
            The ability to miniaturize the device potentially below platforms of 2mm dimensions can produce microchips directed towards local drug delivery. Since there are numerous reservoirs capable of existing on a single chip, a high concentration of drugs can be delivered locally at low systematic concentrations. This controllable form of local drug delivery is advantageous for drugs that produce negative side effects when high systemic concentrations are administered. [1]