Federico Carpi

Transcript

1. Enabling new biomedical and bioinspired mechatronic systems with electroactive elastomeric actuators Federico Carpi f.carpi@qmul.ac.uk 1
2. EAP are materials capable of changing dimensions and/or shape in response to suitable electrical stimuli (Stanford Research Institute) Example: dielectric elastomer actuator Electromechanically Active Polymers (EAP) 2
3. Electromechanically Active Polymers (EAP) 3
4. • thickness compression • surface expansion Electrostatic pressure: p = ε0 εr E2 Thin insulating elastomeric film sandwiched between two compliant electrodes:  4 Dielectric elastomer actuators
5. Thin film of insulating elastomer sandwiched between two compliant electrodes, so as to obtain a deformable capacitor. Electrical charging results in an electrostatic compression of the elastomer. Voltage on V Polymer film Electrodes (on top and bottom surfaces) Voltage off x y z E (electric field) Strain Voltage on V Polymer film Electrodes (on top and bottom surfaces) Voltage off x y z E (electric field) Strain Stanford Research Institute Pelrine, Kornbluh, Pei, et al. Dielectric elastomer actuators (our group) 5
6. How to use the DE actuation principle? Possibilities for new devices and applications limited only by imagination! The greatest value of this technology lies in the fact that it is extremely ‘poor’ (‘poor’ materials and extremely simple mechanism) 6
7. (Stanford Research Institute) (Our group) (Our group) (Our group) Dielectric elastomer actuators
8. Properties: 1) Inherently capable of changing dimensions and/or shape in response to suitable electrical stimuli, so as to transduce electrical energy into mechanical work. In that, they show attractive propeties as engineering materials for actuation: - efficient energy output, - high strains, - high mechanical compliance, - shock resistance, - low mass density, - no acoustic noise, - ease of processing, - high scalability - low cost. 2) Can also operate in reverse mode, transducing mechanical energy into the electrical form. Therefore, they can also be used as mechano-electrical sensors, as well as energy harvesters to generate electricity. 3) Capable of stiffness control. 4) Can combine actuation, sensing and stiffness control, not only in the same material, but actually in the viscoelastic matter they are made of, showing functional analogy with natural muscles artificial muscles Dielectric elastomer actuators
9. … artificial skeletal muscles … Not today Main challenges: - need for improved actuating configurations - need for higher energy density (natural muscle performance can be exceeded, but only in exceptional conditions) - need for lower driving voltages A dream in the biomedical field…
10. Voltage on V Polymer film Electrodes (on top and bottom surfaces) Voltage off x y z E (electric field) Strain Voltage on V Polymer film Electrodes (on top and bottom surfaces) Voltage off x y z E (electric field) Strain Compressive stress (Maxwell stress): ε0 =8.854 pF/m: dielectric permittivity of vacuum E= applied electric field ε= relative dielectric permittivity of the elastomer 2 0 E p    Need for new high-permittivity elastomers: • composites • blends • new synthetic polymers 1) FIRST APPROACH: increasing the material dielectric constant 1) SECOND APPROACH: reducing the film thickness d V E /  V= applied voltage d= thickness Reducing the driving voltages 10
11. What kind of applications are possible today in the fields of biomedical and bioinspired systems? Dielectric elastomer actuators
12. Example from EPFL, Prof. Shea: Array of micro-actuators for cell stretching in vitro (Tissue Engineering) Biomedical applications: studies from other groups
13. Example from Stanford Research Institute : Biomimetic robots Biomimetic applications: studies from other groups
14. Contributions from our lab: Combing dielectric elastomer actuation with fluids as a means of hydrostatic transmission It allows for new devices that might find application as biomedical and bioinspired systems Biomedical & bioinspired applications
15. 1) Braille displays for the blind people 2) Tactile display for smart phones as a helping device for the blind people 3) Haptic displays of tissue compliance for surgical force feedback and medical training 4) Tunable optical lenses for artificial vision systems Latest contributions from our group: combing dielectric elastomer actuation with fluids Biomedical & bioinspired applications
16. 1) Braille displays for the blind people 2) Tactile display for smart phones as a helping device for the blind people 3) Haptic displays of tissue compliance for surgical force feedback and medical training 4) Tunable optical lenses for artificial vision systems Latest contributions from our group: combing dielectric elastomer actuation with fluids Biomedical & bioinspired applications
17. Federico CARPI f.carpi@centropiaggio.unipi.it Full-page refreshable Braille display for the blind people (Braille tablet/e-Book) This is science fiction today! Braille displays
18. Refreshable Braille displays for the blind people STATE OF THE ART Braille displays
19. STATE OF THE ART: piezoelectric cantilever actuators Assembling two lines of Braille cells requires putting two series of actuators nose-to-nose, with their cantilevers pointing away from the cells, laterally 10 cm 3 cm > 20 cm Braille displays
20. STATE OF THE ART: piezoelectric cantilever actuators 25‐30 cm Thickness 3‐4 cm Assembling two lines of Braille cells requires putting two series of actuators nose-to-nose, with their cantilevers pointing away from the cells, laterally Braille displays
21. F. Carpi, G. Frediani, D. De Rossi, “Hydrostatically coupled dielectric elastomer actuators”, IEEE/ASME Transactions On Mechatronics, vol. 15(2), pp. 308-315, 2010. OUR APPROACH: Bubble-like ‘hydrostatically coupled’ DE actuators Braille displays
22. Dielectric elastomer film: silicone (Elastosil RT625, Wacker) processed as a thin film by Danfoss PolyPower Film thickness: about 66 m (two films stacked together) Transmission medium: vegetable (corn) oil Max voltage: 2.25 kV Prototype samples Braille displays
23. - Simple and compact structure; - Ease of fabrication ( low cost) - Electrical safety: i) passive end-effector (no need for insulating coatings) ii) dielectric fluid (as a further protection); - Self-compensation against local deformations caused by the finger: the shape and the thickness uniformity of the active membrane are preserved Attractive features for tactile displays: Braille displays
24. Refreshable Braille cell based on Hydrostatically Coupled DE actuators: External electrodes Internal electrodes TOP PASSIVE MEMBRANE BOTTOM ACTIVE MEMBRANE Plastic frame Braille dot Braille displays
25. Thickness 1‐2 mm 4 cm 25‐30 cm Thickness 3‐4 cm Potential advantages over the state of the art: 1) Compactness 2) Suitability for ‘full-page’ displays 3) Light weight 4) Shock tolerance 5) Low cost state of the art Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Braille displays
26. Prototype samples • Elastomer film: 3M VHB 4905 acrylic polymer. • Bi-axial pre-stretching: 4 times. • Pre-stretched thickness: about 30 µm. • Electrode material: carbon conductive grease. • Transmission medium: silicone grease Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Braille displays
27. Early prototype with Braille dots and spacing oversized (up-scaled) with respect to standards. Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Braille displays
28. Braille dot with standard size (diameter = 1.4 mm; height = 0.7 mm) Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Braille displays
29. 1) Braille displays for the blind people 2) Tactile display for smart phones as a helping device for the blind people 3) Haptic displays of tissue compliance for surgical force feedback and medical training 4) Tunable optical lenses for artificial vision systems Latest contributions from our group: combing dielectric elastomer actuation with fluids Biomedical & bioinspired applications
30. AIM: to provide the blind people with variable dynamic tactile reference points during navigation over touch- screens of smart phones Tactile displays for smart phones
31. TEST CASES: Address book e-mail phone key pad operative system home page Tactile displays for smart phones
32. IDEA: To develop an add-on plastic frame that hosts both the smart phone and variable reference dots made of dielectric elastomer actuators WORK IN PROGRESS….. Tactile displays for smart phones
33. Haptic feedback device for Apple iPod Touch First mass-produced commercial product just released (Bayer - Artificial Muscle, Inc.) A remark: commercially available application
34. 1) Braille displays for the blind people 2) Tactile display for smart phones as a helping device for the blind people 3) Haptic displays of tissue compliance for surgical force feedback and medical training 4) Tunable optical lenses for artificial vision systems Latest contributions from our group: combing dielectric elastomer actuation with fluids Biomedical & bioinspired applications
35. (dots: liver) (dots: stomach) Force feedback in minimally invasive surgery F. Carpi et al. IEEE Transactions on Biomedical Engineering, Vol. 56(9), pp. 2327-2330, 2009. Controlling the stiffness to simulate different tissues Haptic displays of tissue compliance
36. Haptic displays of tissue compliance Medical training
37. 37 (Control via EMG) (Control via respiration) (Control via ECG) Haptic displays of tissue compliance Medical training
38. 1) Braille displays for the blind people 2) Tactile display for smart phones as a helping device for the blind people 3) Haptic displays of tissue compliance for surgical force feedback and medical training 4) Tunable optical lenses for artificial vision systems Latest contributions from our group: combing dielectric elastomer actuation with fluids Biomedical & bioinspired applications
39. Artificial vision (computer vision) systems in the biomedical field: - Social robots (e.g. robot therapy) - Medical diagnostics (e.g. video endoscopes and other optical instrumentation, lab-on-a-chip units, etc.) - etc. Conventional optical focalization : focal length tuning achieved by displacing one or more constant-focus lenses.  moving parts  miniaturization is complex and expensive,  bulky structures Need for tunable-focus lenses with no moving parts Tunable optical lenses for artificial vision systems
40. F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011. Tunable optical lenses for artificial vision systems
41. F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011. Tunable optical lenses for artificial vision systems
42. F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011. Tunable optical lenses for artificial vision systems
43. F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011. Tunable optical lenses for artificial vision systems
44. F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011. 3 cm 10 cm Tunable optical lenses for artificial vision systems
45. Inustrialization of the dielectric elastomer technology is living its infancy nowadays… Dielectric elastomer actuators
46. Main EAP developers Today the EAP field is just starting to undergo transition from academia into commercialization (developers of transducers based on piezoelectric and electrostrictive polymers not included) (acquired by Bayer) EAP industrialization
48. European Scientific Network for Artificial Muscles (ESNAM) www.esnam.eu 1) Austria 2) Bulgaria 3) Czech Republic 4) Denmark 5) Estonia 6) Finland 7) France 8) Germany 9) Greece 10) Hungary 11) Iceland 12) Ireland 13) Israel 14) Italy 15) Netherlands 16) Norway 17) Poland 18) Portugal 19) Romania 20) Serbia 21) Slovak Republic 22) Slovenia 23) Spain 24) Sweden 25) Switzerland 26) United Kingdom 56 Member organizations from 26 European countries: • 40 Research institutes • 10 Companies (3 EAP developers + 7 EAP end-users)
49. Relevant website: “EuroEAP” www.euroeap.eu
50. ‘EAPosters’ ‘EAPodiums’ ‘EAProducts’ Relevant event: “EuroEAP conference” Annual International conference on Electromechanically Active Polymer (EAP) transducers & artificial muscles
51. Relevant event: “EuroEAP conference” EuroEAP 2013 Zurich, Switzerland 25-26 June 2013 www.euroeap.eu • EuroEAP 2011 Pisa, Italy • EuroEAP 2012 Potsdam, Germany