Large Array of Shape Memory Polymer Actuators for Haptics and Microfluidics

My thesis advances the field of shape memory polymer (SMP) actuators by providing a versatile strategy to arbitrarily reconfigure large arrays of densely packed latching soft actuators. It exploits two key intrinsic characteristics of SMPs, which are their multistable nature and their drastic change in Young¿s modulus with temperature, to combine both actuation plus latching in a single actuator. The novel concept consists in individually and selectively addressing arrays of SMP actuators by synchronizing their local Joule heating with a single common air pneumatic supply. Stretchable heaters are integrated and patterned on thin SMP membranes in order to precisely define regions where the stiffness can be changed by over two orders of magnitude. By a timely synchronization of the thermal stimuli with the external air pressure, each actuator can be independently, reversibly, and rapidly latched into any positions. The potential of coupling local Joule heating with global air pneumatic actuation for large arrays of SMP actuators is demonstrated by a 32x24 flexible haptic display and by a 4x4 microfluidic platform. The active layer of the SMP actuator is made of a commercially available SMP material for the SMP membrane and a mixture of carbon black (CB) with soft polydimethylsiloxane (PDMS) for the stretchable heating electrodes. The final SMP actuator geometry corresponds to the best trade-off between displacement and holding force for both haptic and microfluidic applications. The 32x24 flexible haptic display is the first high resolution wearable sleeve capable to vary its surface topology. This device consists of a 40 µm thick SMP membrane, on which a matrix of 25 µm thick stretchable heaters on 4 mm pitch is integrated, interconnected by a 4-layers flexible printed circuit board (PCB) and bonded to a stretchable 3D-printed pneumatic chamber. Each tactile pixel (taxel) can be individually controlled via row/column addressing, requires 250 mW to heat up from 20 °C to 70 °C, and takes 2.5 s to latch to a different state. Each line (row or column) of taxels consumes at most 8 W and the entire haptic display is refreshed in under 1 min 30 s. The haptic display weighs only 55 g and is 2 mm thick. More than 99 % of the 768 taxels are fully functional, with a lifetime in excess of 20000 cycles. The perception tests conducted on the 4x4 tactile tablet with 15 blindfolded sighted users resulted in 98 % correct pattern recognition in less than 10 s exploration, confirming that my SMP actuators are a promising taxel technology. The 4x4 microfluidic platform is the first latching microfluidic array where each valve is directly controlled with a common air pneumatic supply. Its active layer consists of a 50 µm thick SMP membrane, a matrix of 25 µm thick stretchable heaters, and a 37.5 µm thick styrene ethylene butylene styrene (SEBS) membrane. The actuators are electrically interconnected and mechanically bonded to a PCB. On the bottom, a polymethyl methacrylate (PMMA) pneumatic chamber is sealed and, on the top, a micromachined polystyrene (PS) microfluidic chip is bonded. The similarity in design for both normally closed (NC) and normally open (NO) valves enables to implement them in the same chip. These 3 mm in diameter valves remain closed up to 70 mbar of pressure before opening, validating that my SMP actuators are an interesting valve-unit for micropumps, mixers, and multiplexers in microfluidic large scale integration (mLSI) systems

Flexible Zinc-Tin Oxide Thin Film Transistors Operating at 1 kV for Integrated Switching of Dielectric Elastomer Actuators Arrays

Flexible high-voltage thin- lm transistors (HVTFTs) operating at more than 1 kV are integrated with compliant dielectric elastomer actuators (DEA) to create a exible array of 16 independent actuators. To allow for high-voltage operation, the HVTFT implements a zinc–tin oxide channel, a thick dielectric stack, and an offset gate. At a source–drain bias of 1 kV, the HVTFT has a 20 μA on-current at a gate voltage bias of 30 V. Their electrical characteris- tics enable the switching of DEAs which require drive voltages of over 1 kV, making control of an array simpler in comparison to the use of external high-voltage switching. These HVTFTs are integrated in a flexible haptic display consisting of a 4 × 4 matrix of DEAs and HVTFTs. Using a single 1.4 kV supply, each DEA is independently switched by its associated HVTFT, requiring only a 30 V gate voltage for full DEA de ection. The 4 × 4 display operates well even when bent to a 5 mm radius of curvature. By enabling DEA switching at low voltages, flexible metal-oxide HVTFTs enable complex flexible systems with dozens to hundreds of independent DEAs for applications in haptics, Braille displays, and soft robotics

Latchable microfluidic valve arrays based on shape memory polymer actuators

We report arrays of latching microfluidic valves based on shape memory polymers (SMPs), and show their applications as reagent mixers and as peristaltic pumps. The valve design takes advantage of the SMP's multiple stable shapes and over a hundred-fold stiffness change with temperature to enable a) permanent zero-power latching in either open or closed positions (>15 h), as well as b) extended cyclic operation (>3000 cycles). The moving element in the valves consists of a tri-layer with a 50 μm thick central SMP layer, 25 μm thick patterned carbon-silicone (CB/PDMS) heaters underneath, and a 38 μm thick styrene ethylene butylene styrene (SEBS) impermeable film on top. Each valve of the array is individually addressable by synchronizing its integrated local Joule heating with a single external pressure supply. This architecture significantly reduces the device footprint and eliminates the need for multiplexing in microfluidic large scale integration (mLSI) systems

Cerebral cortex expression of Gli3 is required for normal development of the lateral olfactory tract

<div><p>Formation of the lateral olfactory tract (LOT) and innervation of the piriform cortex represent fundamental steps to allow the transmission of olfactory information to the cerebral cortex. Several transcription factors, including the zinc finger transcription factor Gli3, influence LOT formation by controlling the development of mitral cells from which LOT axons emanate and/or by specifying the environment through which these axons navigate. <i>Gli3</i> null and hypomorphic mutants display severe defects throughout the territory covered by the developing lateral olfactory tract, making it difficult to identify specific roles for <i>Gli3</i> in its development. Here, we used <i>Emx1Cre</i>;<i>Gli3</i>^<i>fl/fl</i> conditional mutants to investigate LOT formation and colonization of the olfactory cortex in embryos in which loss of <i>Gli3</i> function is restricted to the dorsal telencephalon. These mutants form an olfactory bulb like structure which does not protrude from the telencephalic surface. Nevertheless, mitral cells are formed and their axons enter the piriform cortex though the LOT is shifted medially. Mitral axons also innervate a larger target area consistent with an enlargement of the piriform cortex and form aberrant projections into the deeper layers of the piriform cortex. No obvious differences were found in the expression patterns of key guidance cues. However, we found that an expansion of the piriform cortex temporally coincides with the arrival of LOT axons, suggesting that <i>Gli3</i> affects LOT positioning and target area innervation through controlling the development of the piriform cortex.</p></div

Simulation of Optical Nanostructures

The goal of this project is to demonstrate by simulations the relevance of fabricating nanowired structures for integrated optical applications. Indeed, subwavelength nanostructures present the advantage of guiding consistently the light, while having also large evanescent fields. Therefore, they are very sensitive to small variations in their surrounding environment. In this report, the powerful of these particular microsystems have been proved by implementing them in a highly sensitive Mach-Zehnder Interferometer (MZI) configuration. In fact, in the device studied and illustrated in Figure A, only the sensing area is made of multiple nanowires. This gives the opportunity to change the light behaviour only in the sensing arm and thus to phaseshift its light beam with respect to the reference one. Additionally to this main concept, two other principles are crucial to design this sensor. Indeed, without adding Anti-Resonant Reflective Optical Waveguides (ARROWs) structures, it would have been impossible to confine the light in the top polymeric layer, since its refractive index is lower than the one of the silicon substrate. Furthermore, the Multi-Mode Interference (MMI) couplers are useful configurations to split and combine light beams, since they are very simple to design and fabricate. Technologically, these structures are fabricated in an hybrid polymer (the Ormocomp) in order to simplify the manufacturing. Indeed, a cost- and time-efficient Nano-Imprint Lithography Process (NIL Process) can be implemented, leading furthermore to precise final structures

La légende Winchester : un mythe patriotique et viril

Catalogue de 92 pages, 82 photographies couleur, 40 noir et blanc.Besse Nadine et Viret Jérôme Luther commissaires de l'expositionMusée d'Art et d'Industrie Saint Etienne éditeur scientifique(92 p. ; 27 cm)Au cinéma comme dans la bande dessinée, les Winchester crachent le feu et ouvrent aux Américains un destin continental. L'épopée romanesque, épique, imaginaire, de la Winchester est unique dans l'univers des armes, on ne lui connaît aucun équivalent, sinon le Colt frontier. L'arme d'épaule et l'arme de poing, figurent au cœur de l'héritage américain. Plus que des objets utilitaires, les 52 Winchester du Musée d'Art et d'Industrie prétextes à cette exposition sont des armes à l'unique fonction commémorative. Cette particularité nous permet d'interroger l'imaginaire lié à cet objet technique et d'aborder quelques traits saillants de la culture américaine. La légende Winchester s'inscrit dans le récit mythique qui a été fait de la conquête de l'Ouest à l'usage des populations citadines de la côte Est. Développée par les média de la seconde moitié du 19e siècle et du 20e siècle, la légende pénètre notre propre culture. Après avoir montré comment la société Winchester fabrique dès 1866 la première véritable carabine à répétition, l'exposition brosse le tableau de la conquête et de ses acteurs. On décrypte dès lors le processus de la constitution du mythe national repris et amplifié par sa mise en spectacle. Le Musée des Armes de Liège, la Bibliothèque Nationale de France, de la Maison de la Chasse et de la Nature de Paris et des collectionneurs privés ainsi que Browning international, complètent les ressources du Musée d'Art et d'Industrie. Le catalogue intitulé « La légende Winchester », très largement illustré par des photographies d'armes, des schémas, des cartes et de nombreuses photographies d'archives, reprend et développe les textes de l'exposition. Trois spécialistes des domaines de l'histoire des Etats Unis, du genre cinématographique western et de la Bande Dessinée, proposent des textes de référence qui éclairent précisément ces thématiques

Multifunctional shape memory electrodes for dielectric elastomer actuators enabling high holding force and low-voltage multisegment addressing

We present a novel configuration of a dielectric elastomer actuator (DEA) using electrodes made of a shape-memory polymer. DEAs are an efficient class of flexible electromechanical transducer. They have been incorporated into a variety of elegant devices, such as microfluidic devices, tunable optics, haptic displays, and minimum-energy grippers, to name a few. Dielectric elastomer minimum energy structures (DEMES) take advantage of the prestretch of the dielectric elastomer actuator to bend a non-stretchable but flexible component to perform mechanical work. DEMES grippers are capable of grasping objects, but with only small to moderate forces. We report on the use of a conductive shape memory polymer (SMP) as the electrode for a DEA gripper. The SMP electrodes allow the DEA to be rigid in the cold state, offering far greater holding force than a conventional DEA. Joule heating applied to the shape memory electrodes soften them, allowing for electrostatic actuation. Cooling then locks in the actuated position without the need for continued power to be supplied. Additionally, the Joule heating voltage is at least one order of magnitude less than electrostatic actuation voltages, allowing for addressing of multiple actuator elements using commercially-available transistors. The shape memory gripper incorporates this addressing into its design, enabling the three segments of each finger to be controlled independently

Device having a plurality of latching micro-actuators and method of operating the same

An actuator device including a plurality of transducer actuators, and a common pneumatic actuation mechanism for shaping the plurality of transducer actuators, wherein each actuator of the plurality of transducer actuators includes a shape memory polymer membrane, an integrated stretchable heater, and a pressure interface to the common pneumatic actuation mechanism

Flexible Active Skin: Large Reconfigurable Arrays of Individually Addressed Shape Memory Polymer Actuators

A high-resolution flexible active skin with a matrix of 32x24 individually addressable tactile pixels on a 4 mm pitch is reported, based on shape memory polymer (SMP) actuators. The intrinsic multistable nature of SMPs, and their more than hundred-fold variation in stiffness over a narrow temperature range, enables dense arrays of actuators exhibiting simultaneously large strokes and high holding forces. The control challenge of addressing a very large number of soft actuators is solved by patterning an array of miniature stretchable heaters on a thin SMP membrane, so that one single pneumatic supply is sufficient to rapidly and selectively reconfigure any or all elements. The device consists of a 40 µm-thick SMP layer, on which 32x24 stretchable heaters are integrated, interconnected by a flexible PCB and bonded to a stretchable 3D-printed pneumatic chamber. Each taxel can be individually controlled via row/column addressing, and requires 2.5 s to latch to a different state. The active skin weighs only 55 g and is 2 mm thick. More than 99% of the 768 taxels are fully functional, with a lifetime in excess of 20’000 cycles. This architecture enables applications in haptic displays, active camouflage, biomimetic robots, microfluidics, and new human machine interfaces