Multistage Multistable Actuation System with scalable stroke, range and force capability based on cooperative electrostatic actuators (MUST ACT)

• Applicant: Professor Dr. Ulrich Mescheder
• Subject Area: Microsystems ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Synthesis and Properties of Functional Materials
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 424626605

At very small distances between the electrodes electrostatic actuators provide high energy density and forces. However, at these conditions actuation range is very limited due to pull-in. For sensor applications (gyros: actuation of primary oscillation, accelerometers: force feedback) these limitations are not really important as here only very low actuation ranges (µm) and very low forces (µN) are needed for the almost massless systems. However, as state of the art, electrostatic actuation cannot be used for large range and forces needed for „macro“ applications. State of the art are inch-worm-motors which provide both, large stroke and force, by cooperative function of two clamping actuators with a “moving” actuator. However, these actuator systems are relatively large (smallest multilayer chip ca. 2x2x2 mm³) and cannot be fabricated with monolithical microfabrication.The motivation of this project is to investigate the scientific fundamentals for the realization of electrostatically driven inch-worm like actuator systems based on a large amount of cooperative electrostatic actuators which are miniaturized, can be fabricated by standard Si-technology and which provide both, large stroke (cm) and large forces (N). For that final vision a better understanding of principles, limitations and boundary conditions are needed for microsystem based actuator systems which are built from a huge amount of miniaturized, multistage, multistable and cooperative electrostatic actuators and which provide scalable step size, total range and forces which all can be scaled over several orders of magnitude. A specific scientific question is the influence of non-linear electrostatic force on mechanical stability of each single, distributed multistable and cooperative sub-actuator and of the total actuator system by coupling. Basic questions here are how many of these cooperative and cascaded single actuators can be integrated for a still stable total system and what are the limits for miniaturization, precision and controllability (e.g. caused by roughness and geometrical deviation of fabricated elements within all the actuators). Additionally, a systematic investigation of limitation and cross-coupling for the inherent capacitive sensing provided by each electrostatic actuator (both, in idle and active state) is needed. Further, understanding of miniaturization and producibility using standard Si-based micro- and nanotechnological processes and of the limits of mechanical and electrical system behavior is needed. Besides homogenous integration concepts (only electrostatic actuators), also heterogeneous systems (e.g. combining electrostatic and piezoelectric actuation) will be investigated which needs a general and parametric system description and fundamental design rules for such a system, especially considering stability. As methods, FEM- and Simulink simulation, micro- und nanotechnology and high resolution characterization techniques will be used.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2206: Cooperative Multilevel Multistable Micro Actuator Systems (KOMMMA)