An interposer to be used in a device for delivering medication to a patient is disclosed. The device includes a reservoir for storing the medication and a needle for releasing the medication in the patient, the interposer configured to mount the reservoir and needle. The interposer comprises a channel for distributing the medication from the reservoir to the needle, a thin membrane defining a portion of the channel as a chamber for receiving the medication, and a piezoelectric transducer positioned on the thin membrane that functions as an actuator for moving the thin membrane toward and away from the chamber of the channel.