Device for attachment to a portable liquid injection device

A device in a form of a removable cap for attachment to a portable liquid injection device and configured to enclose at least a section of the portable liquid injection device having a drug reservoir and to be removed when an injection is performed, comprising:

• at least two conductive electrodes enabling an electrical field to be applied across an entire volume of the drug reservoir of the portable liquid injection device, wherein the at least two conductive electrodes have a height or thickness lower than any dimension other than the height and the thickness, wherein the at least two conductive electrodes including at least two pairs of conductive electrodes, along a circumference of the device, for forming a capacitor, with a total number being at least 2·n electrodes with n≥2,
• wherein the electrode pairs are disposed on an inner circumferential surface of the removable cap, and are geometrically arranged at angular offsets;
• and
• at least three conductive electrodes configured to be separately switched to apply electrical field across the drug reservoir in multiple rotational directions perpendicular to the longitudinal axis of an injection device.