Biomedical applications of micro-electro-mechanical systems, or BioMEMS, is an emerging field that uses techniques adapted from the microelectronics industry to create devices for sensing and manipulating biological material with a precision not previously possible. For example, microfabrication technology is being applied to create drug delivery systems that allow tight control over physical parameters such as fluid flow rates and pressure, enabling precise delivery of concentrated drug solutions in order to meet dosage specifications of drugs. By integrating microfabricated devices such as microneedles and micropumps, very tight control over injection flow rates at given drug concentrations can be achieved. Drug solutions may be administrated as needed by the patient. Thus, the drug concentration in the body may be controlled to achieve either a constant or time-varying drug concentration profile in the body.