Force characterization and analysis of thin film actuators for untethered microdevices

In recent years, untethered microdevices have drawn significant attention due to their small size, weight and their ability to exert forces without the need for wires or tethers. Such microdevices are relevant to implantable biomedical devices, miniature robotics, minimally invasive surgery, and microelectromechanical systems. While devices using these actuators have been widely utilized in pick-and-place and biopsy applications, the forces exerted by these actuators have yet to be characterized and analyzed. Lack of precise force measurements and validated models impedes the clinical applicability and safety of such thin film microsurgical devices. Furthermore, present-day design of thin film microdevices for targeted applications requires an iterative trial-and-error process. In order to address these issues, we present a novel technique to measure the force output of thin film microactuators. Also, we develop and fabricate three designs of residual stress microactuators and use them to validate this technique, and establish a relationship between performance and design parameters. In particular, we find an inverse dependence of the thickness of the actuator and its force output, with 70 nm, 115 nm and 200 nm actuators exerting 7.8 μN, 4.7 μN, and 2.7 μN, respectively. Besides these findings, we anticipate that this microsystem measurement approach could be used for force measurements on alternate microactuators including shape memory, piezo and electromagnetic actuators.