Enabling new biomedical and bioinspired
mechatronic systems
with electroactive smart elastomers
Federico Carpi
1
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)
2
Electromechanically Active Polymers (EAP)
3
Dielectric elastomer actuators
Thin insulating elastomeric film sandwiched between two
compliant electrodes:
Electrostatic pressure: p = ε0εrE2 
• thickness compression
• surface expansion
4
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.
Polymer film
z
y
x
Electrodes (on top
and bottom surfaces)
Strain
Voltage off
V
E (electric field)
Voltage on
(our group)
Stanford Research Institute
Pelrine, Kornbluh, Pei, et al.
5
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!
6
Dielectric elastomer actuators
(Our group)
(Our group)
(Stanford Research Institute)
(Our group)
Dielectric elastomer actuators
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
A dream in the biomedical field…
… artificial skeletal muscles
Main challenges:
… Not today
- 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
- mechanical interfaces with the body
Reducing the driving voltages
Polymer film
z
y
x
Electrodes (on top
and bottom surfaces)
Strain
Voltage off
V
E (electric field)
Voltage on
1) FIRST APPROACH: increasing the material dielectric constant
Compressive stress (Maxwell stress):
p  0  E2
ε0=8.854 pF/m: dielectric permittivity of vacuum
Need for new high-permittivity
elastomers:
• composites
• blends
• new synthetic polymers
E= applied electric field
ε= relative dielectric permittivity of the elastomer
2) SECOND APPROACH: reducing the film thickness
E V / d
V= applied voltage
d= thickness
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Biomedical & bioinspired applications
Contributions from our group:
1) Full-page refreshable and portable Braille displays for the blind
people
2) Wearable tactile display for virtual interactions with soft bodies
3) Haptic or visual displays of tissue compliance or organ motility
4) Artificial ciliary muscles for electrically tuneable optical lenses
for artificial vision systems
5) Artificial muscles for electrically stretchable membrane
bioreactors
Biomedical & bioinspired applications
Contributions from our group:
1) Full-page refreshable and portable Braille displays for the blind
people
2) Wearable tactile display for virtual interactions with soft bodies
3) Haptic or visual displays of tissue compliance or organ motility
4) Artificial ciliary muscles for electrically tuneable optical lenses
for artificial vision systems
5) Artificial muscles for electrically stretchable membrane
bioreactors
Full-page refreshable and portable Braille displays
for the blind people
Artistic view of a possible Braille tablet/e-Book
This is science fiction today!
Full-page refreshable and portable Braille displays
for the blind people
STATE OF THE ART
Full-page refreshable and portable Braille displays
for the blind people
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
3 cm
10 cm
> 20 cm
Full-page refreshable and portable Braille displays
for the blind people
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
Thickness 3-4 cm
25-30 cm
Full-page refreshable and portable Braille displays
for the blind people
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.
Full-page refreshable and portable Braille displays
for the blind people
Prototypes
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
Full-page refreshable and portable Braille displays
for the blind people
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
Full-page refreshable and portable Braille displays
for the blind people
Refreshable Braille cell based on Hydrostatically Coupled DE actuators:
TOP PASSIVE MEMBRANE
Plastic frame
BOTTOM ACTIVE MEMBRANE
External electrodes
Braille dot
Internal electrodes
Full-page refreshable and portable Braille displays
for the blind people
Refreshable Braille cell based on Hydrostatically Coupled DE actuators:
Potential advantages
over the state of the art:
1) Compact size
2) Suitability for ‘full-page’ displays
3) Light weight
4) Shock tolerance
5) Low cost
state of the art
4 cm
Thickness 1-2 mm
25-30 cm
Thickness
3-4 cm
Full-page refreshable and portable Braille displays
for the blind people
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
Full-page refreshable and portable Braille displays
for the blind people
Refreshable Braille cell based on Hydrostatically Coupled DE actuators:
Early prototype with Braille dots and spacing oversized (up-scaled) with respect to standards.
Full-page refreshable and portable Braille displays
for the blind people
Refreshable Braille cell based on Hydrostatically Coupled DE actuators:
Braille dot with standard size (diameter = 1.4 mm; height = 0.7 mm)
Biomedical & bioinspired applications
Contributions from our group:
1) Full-page refreshable and portable Braille displays for the blind
people
2) Wearable tactile display for virtual interactions with soft bodies
3) Haptic or visual displays of tissue compliance or organ motility
4) Artificial ciliary muscles for electrically tuneable optical lenses
for artificial vision systems
5) Artificial muscles for electrically stretchable membrane
bioreactors
Wearable tactile display for virtual interactions
with soft bodies
G. Frediani, D. Mazzei, D. De Rossi, F. Carpi, “Wearable wireless tactile display for virtual
interactions with soft bodies”, Frontiers in Bioengineering and Biotechnology, Vol. 2, 2014.
Wearable tactile display for virtual interactions
with soft bodies
G. Frediani, D. Mazzei, D. De Rossi, F. Carpi, “Wearable wireless tactile display for virtual
interactions with soft bodies”, Frontiers in Bioengineering and Biotechnology, Vol. 2, 2014.
Wearable tactile display for virtual interactions
with soft bodies
Video
G. Frediani, D. Mazzei, D. De Rossi, F. Carpi, “Wearable wireless tactile display for virtual
interactions with soft bodies”, Frontiers in Bioengineering and Biotechnology, Vol. 2, 2014.
Biomedical & bioinspired applications
Contributions from our group:
1) Full-page refreshable and portable Braille displays for the blind
people
2) Wearable tactile display for virtual interactions with soft bodies
3) Haptic or visual displays of tissue compliance or organ motility
4) Artificial ciliary muscles for electrically tuneable optical lenses
for artificial vision systems
5) Artificial muscles for electrically stretchable membrane
bioreactors
Haptic or visual displays of tissue compliance or
organ motility
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.
Haptic or visual displays of tissue compliance or
organ motility
Medical training
(Control via EMG)
(Control via respiration)
(Control via ECG)
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Biomedical & bioinspired applications
Contributions from our group:
1) Full-page refreshable and portable Braille displays for the blind
people
2) Wearable tactile display for virtual interactions with soft bodies
3) Haptic or visual displays of tissue compliance or organ motility
4) Artificial ciliary muscles for electrically tuneable optical lenses
for artificial vision systems
5) Artificial muscles for electrically stretchable membrane
bioreactors
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
Artificial ciliary muscles for electrically tuneable optical lenses
F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.
Artificial ciliary muscles for electrically tuneable optical lenses
F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.
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.
Artificial ciliary muscles for electrically tuneable optical lenses
F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.
Artificial ciliary muscles for electrically tuneable optical lenses
3 cm
10 cm
F. Carpi et al., “Bioinspired tunable lens with muscle-like electroactive elastomers”, Advanced Functional Materials, 2011.
Artificial ciliary muscles for electrically tuneable optical lenses
WORLD’S FASTEST AND THINNEST tuneable lens:
settling time < 175 μs for a 20% change in focal length
• Low-loss silicone
• Be-spoke manufacturing
Cooperation with EPFL
(Prof. Herbert Shea’s group)
L. Maffli, S. Rosset, M. Ghilardi, F. Carpi, H. Shea, "Ultrafast all-polymer electrically tuneable silicone lenses", Advanced
Functional Materials, in press.
Artificial ciliary muscles for electrically tuneable optical lenses
WORLD’S FASTEST AND THINNEST tuneable lens:
L. Maffli, S. Rosset, M. Ghilardi, F. Carpi, H. Shea, "Ultrafast all-polymer electrically tuneable silicone lenses", Advanced
Functional Materials, in press.
Biomedical & bioinspired applications
Contributions from our group:
1) Full-page refreshable and portable Braille displays for the blind
people
2) Wearable tactile display for virtual interactions with soft bodies
3) Haptic or visual displays of tissue compliance or organ motility
4) Artificial ciliary muscles for electrically tuneable optical lenses
for artificial vision systems
5) Artificial muscles for electrically stretchable membrane
bioreactors
Artificial muscles for electrically stretchable membrane bioreactors
SLIDES ON THIS PART HAVE BEEN REMOVED FROM THIS ONLINE
VERSION OF THIS PRESENTATION, AS RESULTS ARE NOT
PUBLISHED YET
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Dielectric elastomer actuators
Inustrialization of the dielectric elastomer technology
is living its infancy nowadays…
EAP industrialization
Today the EAP field is just starting to undergo transition from academia into commercialization
Main EAP developers
(developers of transducers based on piezoelectric and electrostrictive polymers not included)
European Scientific Network for Artificial Muscles (ESNAM)
www.esnam.eu
68 Member organizations from 26 European countries:
Relevant website: “EuroEAP”
www.euroeap.eu
Relevant event: “EuroEAP conference”
Annual International conference on
Electromechanically Active Polymer (EAP)
transducers & artificial muscles
‘EAPodiums’
‘EAProducts’
‘EAPosters’
Relevant event: “EuroEAP conference”
• EuroEAP 2011
• EuroEAP 2012
• EuroEAP 2013
• EuroEAP 2014
- Pisa, Italy
- Potsdam, Germany
- Zurich, Switzerland
- Linköping, Sweden
EuroEAP 2015
Tallin, Estonia
9-10 June 2015
www.euroeap.eu