Bucky gel actuator for morphing applications

Since the demonstration of Bucky Gel Actuator (BGA) in 2005, a great deal of effort has been exerted to develop novel applications for electro-active morphing materials. Three-layered bimorph nanocomposite has become an excellent candidate for morphing applications since it can be easily fabricated, operated in air, and driven with few volts. There has been limited published study on the mechanical properties of BGA. In this study, the effect of three parameters: layer thickness, carbon nanotube type, and weight fraction of components, on the mechanical properties was investigated. Samples were characterized via nano-indentation and DMA. It was found that BGA composed of 22 wt% single-walled carbon nanotubes and 45 wt% ionic liquid exhibited the highest hardness, adhesion, elastic and storage moduli. Most of BGA potential applications would require control over one BGA output: displacement. In this study, various sets of experiments were designed to investigate the effect of several parameters on the maximum lateral displacement of BGA. Two input parameters: voltage and frequency, and three material/design parameters: carbon nanotube type, thickness, and weight fraction of constituents, were selected. A new thickness ratio term was also introduced to study the role of individual layers on BGA displacement. In addition, an important factor in the design of BGA-based devices, lifetime, was investigated. Finally, possible degradation of BGA was studied by repeating displacement measurements after several weeks of being stored. Based on displacement studies, a new model was established utilizing nonlinear regression to predict BGA maximum displacement based on the effect of these parameters. This model was verified by comparing its predictions with other reported results in the literature. The model displayed a very good fit with various reported cases of BGA samples made with different types of CNT and ionic liquid. Microfluidics is a promising field of application for BGA. A brief literature review on the electroactive mechanisms used in microfluidics is presented. Preliminary force studies proved that BGA has the capability to be employed as a microvalve. A flow regulator utilizing a BGA microvalve was designed and fabricated. Flow rate measurements showed the capability of BGA-valve in manipulating the flow rate in different ranges

Süsinikmaterjalist elektroodidega ioonsed ja mahtuvuslikud elektroaktiivsed laminaadid sensorite ning energiakogumisseadmetena

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Kaasaegses elektroonika- ja robootikatööstuses valitseb suundumus miniatuursete, autonoomsete ja läbinisti pehmete seadmete väljatöötamisele, mis ühtlasi tingib huvi sobivate materjalide arenduse vastu. Käesolevas töös käsitletakse antud valdkonnale huvipakkuvat pehmet ioonset elektroaktiivset polümeerset laminaatmaterjali (IEAP), mis koosneb suure-eripinnalistest süsinikelektroodidest, poorsest polümeermembraanist ning ioonvedelikust, mis täidab nii elektroodi kui polümeermembraani poore. Antud laminaatmaterjal on väga multifunktsionaalne – varasemalt on tuntud selle energiasalvestus- ja täituriomadused. Käesolevas töös uuritakse antud materjaliklassi uudset omadust – elektrilaengu genereerimise võimet. Esmalt rakendati IEAP laminaati konfiguratsioonis, mis vastab selle kasutamisele elektromehaanilise täiturina, kuid seda painutati välise jõuga. Painutamise tulemusena genereeris IEAP elektrilaengut proportsionaalselt painutuse ulatusega. Seega on võimalik sama IEAP-i kasutada vaheldumisi nii pehme täituri kui liigutussensorina. IEAP-d iseloomustab suur tundlikkus õhuniiskuse suhtes, sest IEAP koosneb ülihügroskoopsetest koostisosadest. Elektrokeemilise impedantsspektroskoopia meetodil selgus, et õhuniiskuse pöörduva absorptsiooni tõttu võivad IEAP elektrilised omadused muutuda enam kui ühe suurusjärgu ulatuses. Antud töös rakendati IEAP materjali kõrget niiskustundlikkust uudses, ootamatus konfiguratsioonis – hügroelektrilise rakuna. Kui IEAP paigutada kahe erineva suhtelise õhuniiskusega keskkonna eralduspiirile, tekib IEAP elektroodidel elektrilaeng. IEAP hügroelektriline rakk võimaldab koguda elektrienergiat ümbritsevast õhuniiskusest, kusjuures õhuniiskusest genereeritav elektrilaeng ületab enam kui suurusjärgu võrra painutussensorit. Siinkohal on määrava tähtsusega ka IEAP-i energiasalvestiomadused – IEAP hügroelektriline rakk ei vaja välist energiasalvestuselementi, vaid genereeritud elektrilaeng salvestatakse samasse materjaliossa, mis antud laengu genereeris.The modern electronics and robotics industry is interested in development of miniature, autonomous, and fully soft devices; consequently, the research on compatible materials is promoted. This work considers one class of materials – ionic electroactive polymer laminate (IEAP), perspective for the given field. An IEAP consists of carbonaceous electrodes with high specific surface area, a porous polymeric separator, and ionic liquid, which fills the pores in electrode and separator. IEAP is a multifunctional material – it is known for its energy storage and actuation capability. The work at hand explores a novel property of IEAP – generation of electric charge. First, an IEAP laminate was employed in a configuration that corresponds to its use as an electromechanical actuator, but it was bent using an external force. The IEAP generated electric charge proportional to the bending magnitude. Consequently, the same IEAP could be used intermittently as a soft actuator and as a motion sensor. IEAP consists of highly hygroscopic materials, which is expressed in its high sensitivity to ambient humidity. Electrochemical impedance spectroscopy revealed that reversible absorption of ambient humidity changes the electrical properties of IEAP over one order of magnitude. In this work, humidity-sensitive IEAP is employed in a novel, unexpected configuration – as a hygroelectrical cell. If an IEAP is placed between environments with unequal relative humidities, electric charge is formed between the IEAP’s electrodes. An IEAP can be used to harvest electric energy from the ambient humidity, whereas the magnitude of the generated charge is more than one order of magnitude higher than in the case of the same material as a motion sensor. At this point, the energy storage properties of IEAP are essential – an IEAP hygroelectrical cell does not require additional energy storage units; instead, the generated electric charge is stored in the same part of the material, where it was generated