Tindiprinditud pehmed täiturid

Väitekirja elektrooniline versioon ei sisalda publikatsiooneTuleviku biomeditsiini- ja robootikarakenduste täiturite jaoks on vaja usaldusväärseid, korratavaid ja skaleeritavaid valmistamismeetodeid. Johannes Gutenbergi näitel võib printimine ka tehislihaste tootmist revolutsioneerida: printimine võimaldab valmistada ühtlase paksuse ja keeruka mustriga täitureid. Selle doktoritöö raames arendati välja prinditud kolmekihilised kahest elektroodist ja neid eraldavast membraanist koosnevad juhtivpolümeeridel põhinevad täiturid. Tänu analoogsele käitumisele looduslike lihastega kutsutakse neid kuju muutvaid materjale ka tehislihasteks ning just selle funktsionaalse sarnasuse põhjal on tõenäolisteks rakendusvaldkondadeks robootika ja meditsiinitehnoloogia. Prinditud mikrotäiturite elektrilisi, mehaanilisi ja täituromadusi saab muuta kolme peamise strateegia abil. Esiteks modifitseeriti selles doktoritöös kommertsiaalse juhtivpolümeertindi koostist, lisades sinna süsinikaerogeeli. Saadud juhtivpolümeer-süsinik-komposiidil põhineval täituril näitas võrreldes ainult juhtivpolümeertäituriga suuremat jõudu. Teiseks varieeriti täituromaduste täppisreguleerimiseks elektroodi paksust, mis oli vähemalt 20 kihi ulatuses lineaarses sõltuvuses kihtide arvust. Paksuse kasvades suurenesid ka täituri jõud, liigutusulatus, pinnajuhtivus ja mahtuvus. Kolmandaks häälestati täituri sooritusvõimet sobivate alus- ehk membraanimaterjalide valikuga. Nitriilbutadieenkautšukile prinditud õhukesel täituril oli lineaarses liigutusrežiimis suurusjärgu võrra suurem liigutusulatus võrreldes tööstusliku polüvinülideendifluoriidmembraaniga täituriga. Selles töös näidati, et piisksadestusprintimise teel on võimalik valmistada pehmeid elektromehaanilisi süsteeme, hoolimata meetodi mõningatest piirangutest. Sobivalt valitud tindimaterjalid ja häälestatud printimisprotsess võimaldavad juba lähitulevikus valmistada pehmeid ja integreeritud elektromehaanilisi süsteeme täielikult printimise teel.Future soft micro actuator applications for biomedical and soft robotic applications need reliable, repeatable, cost-effective and scalable production methods. As an example of Johannes Gutenberg, printing could also revolutionize the production of artificial muscles – printing allows fabrication of homogeneous actuators with intricate patterns. In this thesis technology for fabricating actuators composed of two conducting polymer-based electrodes and a membrane separating them was developed. The actuators change their shape in response to electrical stimuli. Due to this functional similarity to natural muscles, applications in the fields of medicine and robotics are possible. The properties of printed micro actuators are tunable using various strategies. First, the composition of the conducting polymer ink was modified by adding carbon aerogel to the mix. The resulting composite showed superior force compared to pure conducting-polymer actuators. Second, the electrode thickness was controlled to fine-tune the properties. Increasing the thickness also increased the force, strain and capacitance of the actuator and conductivity of the electrodes. Third, the actuator performance was tailored by the selection of various membrane materials. Printing on spin-coated membranes from nitrile butadiene rubber resulted in extremely thin trilayer actuators that had an order of magnitude higher linear strain compared to commercial polyvinylidene based actuators. This work has showed that despite the known limitations of drop-on-demand printing, it is possible to prepare soft electromechanical systems using this technology. With the selection of compatible materials, and by using various strategies to tune the functional properties of the composite towards more preferred outcome it will be possible in the nearest future to realize applications with fully printed and integrated soft electromechanically active component

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

Investigation of the use of Electro Active Polymer as a Pediatric VAD Driver

Background Heart failure is one of the principal causes of death and disability. The causes of heart failure are many, and a number of technologies have been developed to address this issue by providing support to the failing heart, both as a permanent solution and as a bridge to recovery. These options are called Mechanical Circulatory Support Devices, a particular branch of these devices is the Ventricular Assist Devices, which have been under intense development over the recent years offering a promising solution for this major problem. However, these devices are still bulky, and heavy designed to support failing hearts in the adult population. On the other hand, little has been done in recent times on the development of implantable solutions for heart failure or insufficiency in children. There are many reasons for this, but primarily the relatively small number of children requiring these procedures, the challenges associated with growth, and the lack of physical space for such implantable circulatory support technologies in children are fundamental limitations to the development and deployment of these technologies. Aims of the project The primary purpose of this project was to investigate the development of a new miniaturised self-power VAD that is suitable for paediatrics implantation. This project suggested the use of the newly developed Artificial Muscles to create a mesh that envelops the heart and works as an external assisting circulation mechanism. The same materials could be used to generate electricity when deformed, which can be used to power the proposed device. Critically, the project was to focus on optimising the materials with regard to their operating efficiency to ascertain whether they represent a viable option for VAD production. Materials and Methods A full review of the current available Artificial Muscles was performed to choose the most suitable type for this project. Then different fabrication protocols were developed to make IPMC Artificial Muscles using platinum and palladium coatings. A series of characterization tests were conducted on the fabricated Ionic Polymeric Metal Composites (IPMC) to ensure their quality. Finally, the mechanical and electrical properties were tested and compared with the proposed device requirements. Results The review of Artificial Muscles showed that IPMC would be the best candidate to use in this application. The characterisation tests showed as well that the produced IPMC Artificial Muscles were fabricated to the same standards as those commercially available, and the reported by other investigators. However, these materials showed very low mechanical output with high electrical power consumption, which made them far from practical and not suitable for the proposed application. On the other hand, IPMCs showed promising results as an option to generate electricity to power low consumption implantable devices