We present a flat and cost effective volume displacement actuator based on superabsorbent polymer. It offers slow kinetics and is able to work against reasonable back-pressures, e.g. 0.50 ml in 235 min at 140 kPa. It is predestined for low-cost skin attachable drug delivery devices. The actuator consists of a plastic ring filled with superabsorbent polymer granulate. It is sealed with a thermoplastic elastomeric membrane on one side and a stiff filter membrane on the other side. After adding a defined amount (e.g. 2 or 10 ml) of swelling agent the actuator shows a fast initial volume displacement within a few minutes followed by a slow continuous increase of this volume within hours. Minimized initial volume displacement and maximized displaced volume after 4 h cannot be combined in one actuator. A minimized initial displacement can be as low as 0.10 ml ± 0.03 ml. A maximized displaced volume after 4 h can be 1.71 ml ± 0.18 ml, not considering the initial effect. The back-pressure dependency of one selected actuator design was studied. At a back-pressure of 100 kPa the displaced volume is reduced by 33%. We investigated various actuator designs with varying surface area, hardness of the elastomeric membrane and superabsorbent polymer. Finally, we demonstrate a skin attachable drug delivery system based on the employment of the superabsorbent polymer actuator.

With the proposed easy-to-use interface, intradermal injections and infusions can be performed reliably. Therefore, it is supposed to be an ideal and clinically relevant solution for self-administration of parenteral drugs in home care applications.

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