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Towards Smart Active Skins: Printing flexible TFTs on ultra-low-voltage Dielectric Elastomer Actuators

English title Towards Smart Active Skins: Printing flexible TFTs on ultra-low-voltage Dielectric Elastomer Actuators
Applicant Shea Herbert
Number 165993
Funding scheme Project funding
Research institution Laboratoire des microsystèmes pour les technologies spatiales EPFL - STI - IMT - LMTS
Institution of higher education EPF Lausanne - EPFL
Main discipline Other disciplines of Engineering Sciences
Start/End 01.04.2016 - 31.03.2019
Approved amount 405'854.00
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Keywords (8)

soft robotics; Dielectric Elastomer Actuator; printed electronics; compliant electrode; electroactive polymer; TFT (thin film transistor); self-switching; e-skin

Lay Summary (French)

Lead
Notre peau et nos muscles sont très flexibles et peuvent être étirée de plus de 20%. Mais les robots et les ordinateurs d’aujourd’hui sont rigides. Ceci commence à évoluer avec l’émergence des robots flexibles et des peaux artificielles (e-skins). Ces technologies donnent naissance à des systèmes étirables que nous pouvons porter directement sur ou dans notre corps, par exemple un patch pour un suivi médical, une peau artificielle sur une prothèse de main, ou un exosquelette flexible pour nous aider à marcher. Le progrès est très rapide dans les e-skins, mais il y a moins d’avancées dans les actionneurs souples, or il faut coupler actionneur et capteur pour tout robot ou prothèse active.
Lay summary
Contenu et objectifs du travail de recherche
Les actionneurs flexibles de type « muscle artificiels » (Dielectric Elastomer Actuators ou DEA) se déforment lorsqu’une tension électrique de plus de 1000 volts est appliquée. Un des grands défis est de réduire la tension d’actionnement et d’y intégrer l’électronique de commande afin de rendre ces actionneurs intelligents.
Notre objectif est de développer des muscles artificiels qui fonctionnent à faible tension (seulement 10V) et d’y incorporer des capteurs et de l’intelligence embarquée. Nous allons faire baisser la tension d’actionnent de 100x grâce à des procédés innovants de microfabrication permettant la réalisation de films d’élastomère de haute qualité d’épaisseur de seulement 50 nanomètres. Pour rendre nos muscles artificiels intelligents, nous développerons une nouvelle technologie de transistors flexibles imprimés afin de s’affranchir de l’électronique de commande externe.

Contexte scientifique et social du projet de recherche
Ces deux innovations nous permettront de réaliser des systèmes étirables complexes tels que peau artificielle, implants et prothèses intelligents qui réagissent à des forces externes : par exemple un doigt artificiel capable de ressentir l’objet qu’il tient, ou un robot mou qui manipule facilement un œuf cru sans le casser.
Direct link to Lay Summary Last update: 07.04.2016

Responsible applicant and co-applicants

Employees

Publications

Publication
High-speed mechano-active multielectrode array for investigating rapid stretch effects on cardiac tissue
Imboden Matthias, de Coulon Etienne, Poulin Alexandre, Dellenbach Christian, Rosset Samuel, Shea Herbert, Rohr Stephan (2019), High-speed mechano-active multielectrode array for investigating rapid stretch effects on cardiac tissue, in Nature Communications, 10(1), 834-834.
Dynamically reconfigurable DEAs incorporating shape memory polymer fibers
Aksoy Bekir, Shea Herbert R. (2019), Dynamically reconfigurable DEAs incorporating shape memory polymer fibers, in Electroactive Polymer Actuators and Devices (EAPAD) XXI, Denver, United StatesSPIE, -.
Latchable microfluidic valve arrays based on shape memory polymer actuators
Aksoy Bekir, Besse Nadine, Boom Robert Jan, Hoogenberg Bas-Jan, Blom Marko, Shea Herbert (2019), Latchable microfluidic valve arrays based on shape memory polymer actuators, in Lab on a Chip, 19(4), 608-617.
An open-loop control scheme to increase the speed and reduce the viscoelastic drift of dielectric elastomer actuators
Poulin Alexandre, Rosset Samuel (2019), An open-loop control scheme to increase the speed and reduce the viscoelastic drift of dielectric elastomer actuators, in Extreme Mechanics Letters, 27, 20-26.
An ultra-fast mechanically active cell culture substrate
Poulin Alexandre, Imboden Matthias, Sorba Francesca, Grazioli Serge, Martin-Olmos Cristina, Rosset Samuel, Shea Herbert (2018), An ultra-fast mechanically active cell culture substrate, in Scientific Reports, 8(1), 9895-9895.
Yttrium zinc tin oxide high voltage thin film transistors
Marette Alexis, Shea Herbert R., Briand Danick (2018), Yttrium zinc tin oxide high voltage thin film transistors, in Applied Physics Letters, 113(13), 132101-132101.
Flexible Zinc-Tin Oxide Thin Film Transistors Operating at 1 kV for Integrated Switching of Dielectric Elastomer Actuators Arrays
Marette Alexis, Poulin Alexandre, Besse Nadine, Rosset Samuel, Briand Danick, Shea Herbert (2017), Flexible Zinc-Tin Oxide Thin Film Transistors Operating at 1 kV for Integrated Switching of Dielectric Elastomer Actuators Arrays, in Advanced Materials , 1700880.
Assessing the degradation of compliant electrodes for soft actuators
Rosset Samuel, de Saint-Aubin Christine, Poulin Alexandre, Shea Herbert (2017), Assessing the degradation of compliant electrodes for soft actuators, in REVIEW OF SCIENTIFIC INSTRUMENTS, 88, 105002.
Dielectric Elastomer Actuator for Mechanical Loading of 2D Cell Cultures
Poulin Alexandre, Saygili Demir Cansaran, Rosset Samuel, Petrova Tatjana, Shea Herbert (2016), Dielectric Elastomer Actuator for Mechanical Loading of 2D Cell Cultures, in Lab on a Chip, (19), 3788.

Collaboration

Group / person Country
Types of collaboration
University of Auckland, Biomimetics Labs, prof I. Anderson New Zealand (Oceania)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
LPPI, Université de Cergy-Pontoise France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Hopital Universitaire de Genève, Dr. Serge Grazioli Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
CSEM, group Dr. Cristina Martin Olmos Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Bern University, prof Stephan Rohr Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
- Exchange of personnel
Plymouth University, group of Prof Bing Hu Great Britain and Northern Ireland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
- Exchange of personnel

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
SPIE ElectroActive polymer Actuators and Devices (EAPAD 2019) Talk given at a conference Dynamically reconfigurable DEAs incorporating shape memory polymer fibers 04.03.2019 Denver, United States of America Aksoy Bekir; Shea Herbert;
SPIE Electroactive polymer actuator and devices (EAPAD 2018) Talk given at a conference The NERD setup: assessing the life time of electrodes for dielectric elastomer transducers 05.03.2018 denver, United States of America Poulin Alexandre; Shea Herbert;
Materials Research Society fall meeting (MRS fall 2017) Individual talk Solution processed Y-doped zinc tin oxide with superior performance at very high-voltage 26.11.2017 Boston, United States of America Briand Danick; Marette Alexis; Shea Herbert;
MicroTAS 2017 Poster Array of independent microfluidic valves driven by shape memory polymer actuators using a single pneumatic supply 22.10.2017 Savana, United States of America Shea Herbert; Aksoy Bekir;
Transducers 2017: International Conference on Solid-State Sensors, Actuators and Microsystems Poster Full integration of a dielectric elastomer actautor with a felxible 1 kV thin-film tranistor 22.06.2017 Kaohsiung, Taiwan Shea Herbert; Marette Alexis; Briand Danick;
Materials Research Society Spring Meeting (MRS spring 2017) Individual talk Dielectric Elastomer Actuators for Smart Soft Machines 17.04.2017 Phoenix, United States of America Shea Herbert;
SPIE Electroactive Polymer Actuators and Devices (EAPAD 2017) Individual talk Integration of flexible high-voltage thin-film transistors to drive a matrix of dielectric elastomer actuators 06.03.2017 Denver, United States of America Shea Herbert; Briand Danick; Marette Alexis;
Materials Research Society fall meeting (MRS fall 2016) Individual talk Flexible zinc-tin oxide thin-film transistors operating at 1kV to drive soft actuators 27.11.2016 Boston, United States of America Briand Danick; Poulin Alexandre; Marette Alexis; Shea Herbert;
International conference on Electromechanically Active Polymer (EAP), transducers and artificial muscles (EuroEAP 2016) Poster Flexible 1kV thin-film transistor driving out-of-plane dielectric elastomer actuator 14.06.2016 Copenhagen, Denmark Marette Alexis; Briand Danick; Shea Herbert; Poulin Alexandre;
European Materials Research Society spring meeting (EMRS spring 2016) Individual talk Solution-processed zinc-tin oxide thin-film transistors operating at 1kV on flexible substrate 02.05.2016 Lille, France Briand Danick; Marette Alexis; Shea Herbert; Poulin Alexandre;


Knowledge transfer events

Active participation

Title Type of contribution Date Place Persons involved
VDI-Expertenforum Smart Materials: aus der Forschung in die industrielle Anwendung Talk 08.11.2017 Karlsruhe, Germany Shea Herbert;


Communication with the public

Communication Title Media Place Year
Media relations: radio, television émission CQFD sur le sujet Pourquoi un choc en plein cœur peut tuer ou sauver RTS Western Switzerland 2019
Talks/events/exhibitions MicroCity Portes Ouvertes 2017 Western Switzerland 2017

Awards

Title Year
Best poster award to Alexis Marette at Transducers 2017 for his printed thin film HF TFTs 2017
"Best Student Presentation Award” at the SPIE Smart Structures NDE 2016 conference in Las Vegas in March 2016 for his wrok on ultrathin printed DEAs. 2016

Associated projects

Number Title Start Funding scheme
184661 Printed untethered soft robots based on miniature low-voltage actuators 01.05.2019 Project funding
177255 WeCare: Cognitive-Multisensing Wearable Sweat Biomonitoring Technology for Real-Time Personalized Diagnosis and Preventive Health Care 01.06.2018 Sinergia
153365 MUSCLELAB "Elastomer-based structures for human cell force measurements" 01.03.2015 Project funding
153122 Printing flexible TFTs on low-voltage Dielectric Elastomer Actuators for Soft Smart Machines 01.04.2014 Project funding

Abstract

BackgroundSoft and stretchable transducers are particularly well adapted to the field of smart wearable and implantable devices, such as biomonitoring sensors and implants, actuators for soft exoskeletons, or generators capable of harvesting electric energy from body motion. These wearable devices will transform healthcare, our workplace, sports, merging continuous distributed monitoring and bio-data analysis, with distributed actuation. Today’s e-skins are evolving very rapidly, but lack integrated actuation needed to extend their functionality beyond sensing.Dielectric elastomer actuators (DEAs) are particularly interesting actuators for wearable devices or soft robotics, with actuation pressures of 1 bar, actuations stains of over 100%, and fast speed (less than 1 ms). DEAs consist of a thin dielectric membrane sandwiched between two compliant electrodes. The same structure can also serve as a stretchable strain sensor. The main limitation of DEAs is their high actuation voltage, typically several kV, which causes the control electronics to be bulky and expensive, nearly impossible to integrate in a wearable device. Our GoalsTo incorporate distributed actuation in active smart skins or soft robotics driven by DEAs, we plan two parallel activities: a)Develop printed flexible thin-film transistors (TFTs) capable of driving self-sensing DEAs at 500 V. We will couple the gate of the TFTs to strain-sensitive resistances to provide distributed intelligence through self-switching. We work at 500 V in order to demonstrate the concept using our existing DEA technology. This will lead to truly smart soft machine able to rapidly mechanically react to their environment with complex behaviors, yet without the need for complex centralized control electronics. b)To fully realize the longer-term dream of smart active skins, we propose a higher risk activity to dramatically reduce the DEA operating voltage from kV to 10 V while keeping actuation force. One key missing technology for this ambitious goal is compliant electrodes specifically tailored for sub-µm elastomer membranes. We will develop electrodes thinner and vastly softer than those reported to date as well as deposition and patterning methods on very thin elastomer films (50 nm). Coupled with other ongoing work in our lab on thin elastomer membranes, this will lead to 10 V stacked DEAs, revolutionnizing where DEAs can be used.Challenges and methodsLow-voltage TFTs are widely used in flat-panel displays, but printed and flexible TFTs working at 500 V are nearly unheard of due to design, materials and processing challenges. We propose to print TFTs directly on flexible frames supporting the DEAs. Using inorganic oxide semiconductors and design strategies such as offset gates will lead to TFTs capable of switching DEAs at over 500 V with a gate voltage lower than 50 V at high speed (>100 Hz.)To implement self-sensing, strain-sensitive resistive tracks will be patterned on the actuator’s elastomer membrane to provide low voltage control of the gate voltage of the DEAs as a function of the deformation. Gold ion implantation, as well as pad-printed conductive silicone compounds will be used for the piezo-resistances. Given typical RC time constants and for mechanical reasons, existing carbon-based electrodes cannot be used for 50 nm thick DEAs required for 10 V operation. We will be pushing the boundaries of what is possible, as we will develop electrodes with the electrical conductivity of a metal but with the mechanical properties of an elastomer, that can be patterned on sub-µm thick elastomer films. Depositing our novel electrodes on ultra-thin (down to 50nm) silicone elastomer membranes (made in another project in our lab by bottom-up fabrication processes, such as Langmuir-Blodgett methods), we will develop DEAs operating with high strain and high efficiency down to 10V, in a stacked configuration to attain high force.Impact & significanceThe large actuation strain of DEAs, their high actuation pressure and intrinsic compliance give them unmatched performance for many applications, such as tunable optics, soft robotics, braille displays, etc. However, the high voltages required to drive them have limited their use.DEAs with reliable self-switching at 500 V, which can be demonstrated with existing DEA technology, and further on DEAs operating at 10V will have a transformative impact in the field. The impact will be most spectacular for complex systems comprised of a large number of independent actuators - such as a braille displays or exoskeletons - which are impractical to realize with DEA technology today because the size and cost of the drive electronics. This project will enable a completely untapped new range of applications, in particular in the field of wearable and implanted devices or biomedical applications.
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