Manufacturability of a Printed Resistance-Based Multiplexing Scheme for Smart Drug Packaging

The efficacy of drug plans can critically depend on patient's adherence to a prescribed intake schedule. Detection of the rupture of blisters in drug packages through circuits printed on the package allows medical practitioners to monitor patient's compliance. In the current state of the art, each blister is overprinted with a conductive track and their rupture is detected by a dedicated pin in a reusable integrated circuit (IC) that records and communicates the results. In this paper, we are reporting on the development of a smart drug package based on the multiplexed detection of printed resistive tracks monitored by an IC with a reduced number of pins, which lowers the cost and the complexity of components and assembly. Using a generalized formalism, it is shown how manufacturing tolerances limit the achievable multiplexing factor. Tests with our chosen screen printing technique allow us to conclude that a factor of 3 is achievable. This was verified by the design and the fabrication of a multiplexed 28-blister package and corresponding interrogation system. A detailed analysis reveals the limits of the technique and points to factors that may reduce variability, and the robustness of the technique is demonstrated by environmental and mechanical tests. This technique is shown to be a viable way of reducing the complexity of integration of printed and conventional electronics.