A controlled-release microchip

Much previous work in methods of achieving complex drug-release patterns ha s focused on pulsatile release from polymeric materials in response to spec ific stimuli(1), such as electric(2-5) or magnetic(6,7) fields, exposure to ultrasound(7,8), light(9) or enzymes(10), and changes in pH(11) or tempera ture(12-14), An alternative method for achieving pulsatile release involves using microfabrication technology to develop active devices that incorpora te micrometre-scale pumps, valves and flow channels to deliver liquid solut ions(15,16). Here we report a solid-state silicon microchip that can provid e controlled release of single or multiple chemical substances on demand. T he release mechanism is based on the electrochemical dissolution of thin an ode membranes covering microreservoirs filled with chemicals in solid, liqu id or gel form. We have conducted proof-of-principle release studies with a prototype microchip using gold and saline solution as a model electrode ma terial and release medium, and we have demonstrated controlled, pulsatile r elease of chemical substances with this device.