Microhydraulic Actuation

Transcription

1 Materials Integration: from Nanoscale to Waferscale Microhydraulic Actuation This material is based upon work supported by the Assistant Secretary of Defense for Research and Engineering under Air Force Contract No. FA C-0002 and/or FA D Any opinions, findings, conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Assistant Secretary of Defense for Research and Engineering. Distribution Statement A: Approved for public release: distribution unlimited Massachusetts Institute of Technology. Delivered to the U.S. Government with Unlimited Rights, as defined in DFARS Part or 7014 (Feb 2014). Notwithstanding any copyright notice, U.S. Government rights in this work are defined by DFARS or DFARS as detailed above. Use of this work other than as specifically authorized by the U.S. Government may violate any copyrights that exist in this work. Dr. Jakub Kedzierski MIT Lincoln Laboratory 6 March 2018

2 Actuator Landscape Power density and efficiency are desired characteristics for all actuators, but no micro-actuators have both Our goal: Build an efficient and powerful microactuator Efficiency (%) Max Electroactive polymer 1.9 g Piezoelectric stepping actuator 0.46 g Motor Muscle 150 g Motor Max Piezoelectric bimorph Tesla Model S Drive Motor Internal Combustion Engines Shape Memory Alloys Macro-actuators Micro-actuators Power Density (W/kg) Microhydraulic Actuation - 2

3 Physical Basis Electrowetting Surfaces can electrically change from hydrophobic to hydrophilic Motion Water Drop E-field 1 mm Electrowetting of a water drop in oil Microhydraulic Actuation - 3

4 Actuator Structure and Operation Actuator consists of a glass electrode array and a polyimide droplet array separated by a droplet layer Electrodes can distort droplets to produce a net force moving the droplet array Droplet Array Thin (5 10 µm) polyimide with water droplets attached Electrode Array Multi-phase electrodes with an electrowetting dielectric Oil Polyimide Water Droplet Droplet Array Phase 1 Phase 2 Phase 3 Phase 4 One Cycle 48 µm One Step Off/On Electrodes 12 µm Electrode Array Microhydraulic Actuation - 4

5 Reference Rail Phase Rails Actuator at Rest When brought in contact, droplet array and electrode array snap together and self-align Contact fixes the location in two dimensions X position is fixed by rails Z positon is fixed by droplet height Y position is free for translation 250 µm Rails Electrode Array Droplet Array Microhydraulic Actuation - 5

6 Actuator in Motion Slow Linear Actuation Step Frequency 5 Hz 50 µm Fast Linear Actuation Step Frequency 4000 Hz 20 cyc 250 µm Precision 1 µm Accuracy 12 µm Max Step Frequency Hz Max (unloaded) Velocity 192 mm/s Acceleration 3.07 km/s 2 Max Force/Weight Ratio 5500 Max Power Density 1 W/g Efficiency at Max Power 60% Microhydraulic Actuation - 6

7 Mechanical Characterization Loaded Maximum Output Force (mn/m) Cycle Frequency (khz) Oil-Water Surface Tension g Maximum Force V b = 37.2 V E max E hyst Expected Max Force Maximum Unloaded Velocity V t = V Actuation Velocity (mm/s) Loaded Maximum Power Density (kw/kg) Cycle Frequency (khz) V b = 37.2 V 1.2 V t = V Maximum Output Power Density Low Velocity Low Output Force Actuation Velocity (mm/s) Microhydraulic Actuation - 7

8 Efficiency and Power Density Power density of the 48 µm pitch design is already comparable to electric motors Scaling improves power density at a quadratic rate Projected power density at 15 µm pitch is ~10 W/g Efficiency (%) Ultrasonic Motor USR30 17 g Max Electroactive Polymer 1.9 g Piezoelectric Stepping Actuator Microhydraulic Actuators 100 µm Pitch 0.46 g Motor Muscle 150 g Motor Max Piezoelectric Bimorph 48 µm Pitch Internal Combustion Engines Tesla Model S Drive Motor Shape Memory Alloys 15 µm Pitch Power Density (W/kg) Microhydraulic Actuation - 8

9 Rotational Actuation In Air 250 µm Precision 0.03 Accuracy 0.17 Max velocity 2700 /s Max acceleration 43 M /s 2 Torque 84 mn-mm 200 Hz Step Freq. between Holds 4000 Hz Step Freq. between Holds Microhydraulic Actuation - 9

10 Rotational Actuation Macroscopic 4000 Hz Step Freq. 100 cyc between Holds Moving 5 mm Beam Splitter (0.37 g) 1000 Mass of Actuator Microhydraulic Actuation - 10

11 Applications Shorter Term Building the world s smallest stepper motor (0.1 g) with precise positioning for cameras or laser communication 5 mm 0.2 mm Building small precise linear actuators with capability to move mirrors or lenses Microhydraulic Actuation - 11

12 Applications Longer Term Exoskeleton with artificial muscle Exoskeleton Shape-change glass and other shapechange materials Artificial wings Shape-change glass Artificial Wings Microhydraulic Actuation - 12

13 Conclusion Microhydraulic actuation is a new MEMS technology developed at Lincoln Laboratory under the Advanced Devices Line program Allows powerful, efficient, and versatile actuation on a small scale Allows very precise and rapid positioning Excellent metrics even at an early stage of development Many metrics improve with shrinking droplet pitch Liquid/solid composition of microhydraulic components offers unique challenges and opportunities Microhydraulic Actuation - 13

14 Acknowledgments Thanks to the MEL team that made this possible: Joel Maldonado, Hero Chea, Matt Cook, and others Thanks to Eric Holihan for help with assembly Thanks to the Advanced Device Line for supporting this research Microhydraulic Actuation - 14