Printing technologies are modifying the burgeoning field of deformable sensors and electronics by providing cost-effective routes for processing new electronic materials. Inkjet-printing has been established in extensive research work as a low-cost, prototyping technique able to pattern conductive material on a polymeric substrate without the need for a mask. Despite these established advantages, inkjet-printing is still a fairly young technology, therefore the reliability of both the fabrication process and the fabricated material systems is still a key point to achieve competitive devices. This project was devoted to evaluating inkjet-printing technology as a fabrication technique for the realization of deformable strain sensors. Initially, process parameters and their effect on the performances of printed devices were evaluated by realizing and electro-mechanical characterizing inkjet printed deformable silver nanoparticles electrical interconnections of different geometries on polyethylen-terephthalate (PET) and polydimethylsiloxane (PDMS) substrates. Inkjet-printing on PET surface is a well-established practice; however, it is fundamental a deep knowledge of the printing procedure to realize high-quality devices. The ability of the inkjet-printing technique of the realization of reliable fully-inkjet-printed uniaxial resistive strain mapping array on PET substrate was assessed. A carbon nanotubes matrix was selected as strain-sensing material and its sensing ability was characterized and optimized through in-situ electro-mechanical tests on single strain sensors. The fabricated sensors array was characterized through a confined electro-mechanical tensile test in which non-homogeneous strain states were applied. Results showed the mapping capability of a fully-inkjet-printed deformable sensors array that is able to measure different local strains on the substrate surface, paving the way for using inkjet-printing technique for the realization of sensors with a larger number of interesting applications. A different sensing mechanism was exploited for the realization of inkjet-printed deformable wireless strain sensors. An inductive inkjet-printed strain-sensitive coil was designed. In order to optimize strain-sensor sensitivity, it is fundamental to understand the relation between inductance and coil geometry. Hence, a numerical analysis was performed in order to evaluate the effect of the geometrical parameters on the nominal inductance of the coil and thus the inductor strain-sensitivity.
Le nuove tecnologie di stampa stanno modificando il settore dell’elettronica deformabile grazie alla possibilità di processare nuovi materiali funzionali. In particolare, la stampa a getto d'inchiostro è emersa come un’innovativa tecnica di prototipazione a basso costo in grado patternare materiale conduttivo su substrati polimerici. Nonostante i consolidati vantaggi, la stampa a getto d'inchiostro è una tecnologia abbastanza giovane, che non permette ancora di realizzare dispositivi competitivi. In questa tesi si è studiata ed utilizzata la tecnica di stampa a getto d'inchiostro per la realizzazione di sensori di deformazione su substrato polimerico. Inizialmente, è stata eseguita l’ottimizzazione dei parametri di fabbricazione ed è stato valutato il loro effetto sulle prestazioni dei dispositivi stampati. Questa analisi è stata effettuata tramite la realizzazione e caratterizzazione elettro-meccanica di interconnessioni elettriche conduttive di diverse geometrie stampate su due differenti substrati polimerici, PET e PDMS, con un inchiostro di nanoparticelle d’argento. E’ stato progettato e realizzato un array di sensori di deformazione resistivi uniassiali. E’ stato formulato e utilizzato per la realizzazione degli elementi sensibili un inchiostro di nanotubi di carbonio. Test elettro-meccanici su singoli sensori di deformazione hanno permesso di valutare e attestare le capacità della matrice di nanotubi di essere sensibile alla deformazione. E’ stato, infine, progettato e realizzato un array di sensori utilizzando solo la tecnica di stampa a getto di inchiostro. L'array è stato caratterizzato attraverso prove di trazione elettro-meccaniche confinate in cui sono stati applicati stati di deformazione non-omogenee. I risultati hanno dimostrato la capacità dell’array di mappare i differenti sforzi locali sulla superficie del substrato. Si è, quindi, dimostrata la capacità della stampa a getto di inchiostro di poter realizzare sensori deformabili a basso costo, che possono essere utilizzati per molte interessanti applicazioni. Un differente meccanismo di rilevamento è stato utilizzato per la realizzazione di sensori di deformazione wireless. Sono stati progettati sensori induttivi di deformazione. Al fine di ottimizzare la sensibilità del sensore, è stata eseguita un'analisi numerica per poter correlare la geometria del sensore con il suo valore di induttanza e, quindi, la sua sensibilità alla deformazione.
Inkjet-printing technique for deformable strain sensors
COSTA ANGELI, MARTINA AURORA
Abstract
Printing technologies are modifying the burgeoning field of deformable sensors and electronics by providing cost-effective routes for processing new electronic materials. Inkjet-printing has been established in extensive research work as a low-cost, prototyping technique able to pattern conductive material on a polymeric substrate without the need for a mask. Despite these established advantages, inkjet-printing is still a fairly young technology, therefore the reliability of both the fabrication process and the fabricated material systems is still a key point to achieve competitive devices. This project was devoted to evaluating inkjet-printing technology as a fabrication technique for the realization of deformable strain sensors. Initially, process parameters and their effect on the performances of printed devices were evaluated by realizing and electro-mechanical characterizing inkjet printed deformable silver nanoparticles electrical interconnections of different geometries on polyethylen-terephthalate (PET) and polydimethylsiloxane (PDMS) substrates. Inkjet-printing on PET surface is a well-established practice; however, it is fundamental a deep knowledge of the printing procedure to realize high-quality devices. The ability of the inkjet-printing technique of the realization of reliable fully-inkjet-printed uniaxial resistive strain mapping array on PET substrate was assessed. A carbon nanotubes matrix was selected as strain-sensing material and its sensing ability was characterized and optimized through in-situ electro-mechanical tests on single strain sensors. The fabricated sensors array was characterized through a confined electro-mechanical tensile test in which non-homogeneous strain states were applied. Results showed the mapping capability of a fully-inkjet-printed deformable sensors array that is able to measure different local strains on the substrate surface, paving the way for using inkjet-printing technique for the realization of sensors with a larger number of interesting applications. A different sensing mechanism was exploited for the realization of inkjet-printed deformable wireless strain sensors. An inductive inkjet-printed strain-sensitive coil was designed. In order to optimize strain-sensor sensitivity, it is fundamental to understand the relation between inductance and coil geometry. Hence, a numerical analysis was performed in order to evaluate the effect of the geometrical parameters on the nominal inductance of the coil and thus the inductor strain-sensitivity.File | Dimensione | Formato | |
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https://hdl.handle.net/10589/166577