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