A wearable, self-contained drug infusion device is disclosed that is capable of achieving the precise flow rate control needed for dose-critical drugs such as insulin. In preferred embodiments of the device, piezoelectrically-actuated valve or pump structures are used in combination with thermal flow sensors and closed-loop control circuits for providing the desired flow rate control. The miniaturization that is possible with each of these technologies allows the drug infusion device to have very small dimensions so that it can be worn by the user with a minimum of discomfort and inconvenience, while at the same time allowing for the close control over flow rate that is required for safe and effective delivery of insulin and other drugs. Preferred embodiments of the device have a two-part construction in which the more expensive electronic components are housed in a reusable portion and the fluid delivery components are housed in a separable disposable portion. This is advantageous not only in reducing the effective cost of the device to the user, but also in assuring sterility of the drug and preventing fluid communication of the reusable portion by confining the fluid flow path to the disposable portion. Also, because control over the flow rate of the drug is carried out electronically, variable and/or programmable control over the flow rate is possible. This renders the device particularly suitable for those drugs, such as insulin, that require different delivery rates at different times for different patients. Preferred embodiments of the invention may also utilize a wireless unit for controlling the operation of the drug infusion device. The wireless unit may communicate with the reusable portion of the drug infusion device using radio frequency (RF) methods, optical infrared (IR) methods, or other methods.
