High reliability nanosandwiched Pt/Ti multilayer electrode actuators for on-chip biomedical applications.

Microactuators provide the main driving force for fluid pumping in microfluidic devices and thus play an important role in on-chip biomedical applications. Interdigitated electrode based electrochemical actuators have provided a viable choice for effective actuation with advantages of flexible controllability, biocompatibility and ease of fabrication. However, the current feature size of a typical electrode structure is around 100 μm, which is relatively large for device miniaturization and integration. Further decrease in the feature size will lead to dramatic decrease in the reliability and lifetime of the actuators, caused by metal delamination. In this work, we propose a novel design of electrodes to fabricate a new type of microactuator with high reliability. To prevent the occurrence of delamination, a nanosandwiched multilayer structure of titanium/platinum is used to construct the conductive metal layer for the interdigitated electrodes. The feature size of the electrodes is greatly reduced to 20 μm where we have reduced the size by 80% of the similar structures reported previously. At the same time, the lifetime of the new electrodes has been dramatically increased to over 400% as compared to the conventional design. With these remarkable improvements in the electrode design, we have fabricated a prototype microfluidic device integrating the new microactuator for drug tests in cancer therapy, demonstrating its usefulness for on-chip biomedical applications.