US Patent 11285306 Transdermal drug delivery devices and methods

A transdermal drug delivery device includes a reservoir, a transdermal membrane, a piston, a control rod, a spring, and a rotational cam. The reservoir is configured to hold a formulation. The transdermal membrane is configured to allow the formulation from the reservoir to pass therethrough. The piston is configured to move into the reservoir. The control rod is attached to the piston and includes a plurality of teeth thereon. The spring is configured to apply force to the control rod in the direction of the reservoir. The rotational cam has a first camming surface and a second camming surface that are configured to engage with the plurality of teeth. The rotational cam, when rotated, is configured to disengage the first camming surface from a first tooth of the plurality of teeth, thereby allowing the spring to advance the piston into the reservoir to expel the formulation onto the transdermal membrane.