EAP are materials capable of changing dimensions and/or shape

1. Enabling new biomedical and bioinspired mechatronic systems with electroactive elastomeric actuatorsFederico Carpif.carpi@qmul.ac.uk

2. Electromechanically Active Polymers (EAP) EAP are materials capable of changing dimensions and/or shape in response to suitable electrical stimuli Example: dielectric elastomer actuator (Stanford Research Institute)

3. Electromechanically Active Polymers (EAP)

4. Dielectric elastomer actuators Thin insulating elastomeric film sandwiched between two compliant electrodes: • thickness compression Electrostaticpressure: p = ε0εrE2  • surface expansion

5. Dielectric elastomer actuators 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. (our group) Stanford Research Institute Pelrine, Kornbluh, Pei, et al.

6. How to use the DE actuation principle? The greatest value of this technology lies in the fact that it is extremely ‘poor’ (‘poor’ materials and extremely simple mechanism) Possibilities for new devices and applications limited only by imagination!

7. Dielectric elastomer actuators (Our group) (Stanford Research Institute) (Our group) (Our group)

8. Dielectric elastomer actuators Properties: • 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 alsobe used as mechano-electrical sensors, as well as energy harvesters to generate electricity. • 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

9. A dream in the biomedical field… … artificial skeletal muscles • 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 … Not today

10. Reducing the driving voltages 1) FIRST APPROACH: increasing the material dielectric constant Compressive stress (Maxwell stress): ε0=8.854 pF/m: dielectric permittivity of vacuum E= applied electric field ε= relative dielectric permittivity of the elastomer • Need for new high-permittivity • elastomers: • composites • blends • new synthetic polymers 1) SECOND APPROACH: reducing the film thickness V= applied voltage d= thickness

11. Biomedical & bioinspired applications Contributions from our group: 1) Braille displays for the blindpeople 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) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors

12. Biomedical & bioinspired applications Contributions from our group: 1) Braille displays for the blindpeople 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) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors

13. Braille displays Full-page refreshable Braille display for the blind people (Braille tablet/e-Book) This is science fiction today!

14. Braille displays Refreshable Braille displays for the blind people STATE OF THE ART

15. 3 cm 10 cm > 20 cm Braille displays 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

16. Thickness 3-4 cm 25-30 cm Braille displays 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

17. Braille displays OUR APPROACH: Bubble-like ‘hydrostatically coupled’ DE actuators F. Carpi, G. Frediani, D. De Rossi, “Hydrostatically coupled dielectric elastomer actuators”, IEEE/ASME Transactions On Mechatronics, vol. 15(2), pp. 308-315, 2010.

18. Braille displays Prototype samples 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

19. Braille displays Attractive features for tactile displays: • 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

20. Braille displays Refreshable Braille cell based on Hydrostatically Coupled DE actuators: TOP PASSIVE MEMBRANE BOTTOM ACTIVE MEMBRANE Plastic frame External electrodes Braille dot Internal electrodes

21. 4 cm Thickness 3-4 cm Thickness 1-2 mm 25-30 cm Braille displays Refreshable Braille cell based on Hydrostatically Coupled DE actuators: • Potential advantages • over the state of the art: • Compactness • Suitability for ‘full-page’ displays • 3) Light weight • 4) Shock tolerance • 5) Low cost state of the art

22. Braille displays Refreshable Braille cell based on Hydrostatically Coupled DE actuators: 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

23. Braille displays Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Early prototype with Braille dots and spacing oversized (up-scaled) with respect to standards.

24. Braille displays Refreshable Braille cell based on Hydrostatically Coupled DE actuators: Braille dot with standard size (diameter = 1.4 mm; height = 0.7 mm)

25. Biomedical & bioinspired applications Contributions from our group: 1) Braille displays for the blindpeople 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) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors

26. Tactile displays for smart phones AIM: to provide the blind people with variable dynamic tactile reference points during navigation over touch-screens of smart phones

27. Tactile displays for smart phones TEST CASES: Address book e-mail phone key pad operative system home page

28. Tactile displays for smart phones 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…..

29. A remark: commercially available application First mass-produced commercial product just released (Bayer - Artificial Muscle, Inc.) Haptic feedback device for Apple iPod Touch

30. Biomedical & bioinspired applications Contributions from our group: 1) Braille displays for the blindpeople 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) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors

31. Haptic displays of tissue compliance Force feedback in minimally invasive surgery (dots: liver) Controlling the stiffness to simulate different tissues (dots: stomach) F. Carpi et al. IEEE Transactions on Biomedical Engineering, Vol. 56(9), pp. 2327-2330, 2009.

32. Haptic displays of tissue compliance Medical training

33. Haptic displays of tissue compliance Medical training (Control via EMG) (Control via respiration) (Control via ECG)

34. Biomedical & bioinspired applications Contributions from our group: 1) Braille displays for the blindpeople 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) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors

35. Electrically tuneable optical lenses for artificial vision systems • 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

36. Artificial ciliary muscles for electrically tuneable optical lenses F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.

37. Artificial ciliary muscles for electrically tuneable optical lenses F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.

38. Artificial ciliary muscles for electrically tuneable optical lenses Bioinspired lens Human crystalline F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.

39. Artificial ciliary muscles for electrically tuneable optical lenses F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.

40. 3 cm 10 cm Artificial ciliary muscles for electrically tuneable optical lenses F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.

41. Artificial ciliary muscles for electrically tuneable optical lenses Coordination of a European project proposal under evaluation: EMBODI-EYED: EMBODied vIsion through Evolving eYes with bioinspirEd Design

43. Biomedical & bioinspired applications Contributions from our group: 1) Braille displays for the blindpeople 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) Artificial ciliary muscles for electrically tuneable optical lenses for artificial vision systems 5) Artificial muscles for electrically stretchable membrane bioreactors

44. Artificial muscles for electrically stretchable membrane bioreactors Porous electroactive membranes as stretchable substrates for dynamic cell culture of intestinal epithelial cells Development of EAP porous membranes capable of electrically-controllable biomimetic peristaltic motion and variable mechanical stiffness. FINAL AIM: to develop experimental models of intestinal barrier, In order to study: 1) The effects of cell exposure to nanoparticles, as a function of the substrate’s motion; 2) The effect of aging, simulated as an increase of the substrate’s stiffness (Partnership in an ongoing Italian research project)

45. Artificial muscles for electrically stretchable membrane bioreactors Porous electroactive membranes as stretchable substrates for dynamic cell culture of intestinal epithelial cells • ORIGINAL APPROACH: • Growth of epithelial cell (CACO-2, heterogeneous human epithelial colorectal adenocarcinoma cells) monolayers; • Culture medium: DMEM • Cell cultures on circular porous EAP membranes that undergo controllable cyclic stretching in a physiologically relevant environment.

46. Artificial muscles for electrically stretchable membrane bioreactors Porous electroactive membranes as stretchable substrates for dynamic cell culture of intestinal epithelial cells

47. Artificial muscles for electrically stretchable membrane bioreactors Porous electroactive membranes as stretchable substrates for dynamic cell culture of intestinal epithelial cells

48. Artificial muscles for electrically stretchable membrane bioreactors Porous electroactive membranes as stretchable substrates for dynamic cell culture of intestinal epithelial cells • Different characterisations, such as: • 1) Optical microscopy: • itrequiresfullytransparentdevices • 2) Atomic force microscopy: • to assess the short-term morphological and mechanical changes induced on the epithelial cells by the moving substrate. (View from bottom of the bioreactor)

49. Artificial muscles for electrically stretchable membrane bioreactors In situ nanomechanical characterisation via AFM fluorescent microspheres AFM cantilever 3T3 cell

50. Artificial muscles for electrically stretchable membrane bioreactors In situ nanomechanical characterisation via AFM Experimental set-up