The area of Biomedical Engineering dealing with the interaction between electronic technologies and human body is increasingly gaining relevance and has long since revolutionized the process of doing therapy and diagnosis. The design of medical devices able to operate in an intense interaction with organs and tissues is particularly attractive. They are sophisticated tools capable to monitor electrical and chemical biological signals, replace parts of the body and restore compromised physiological functions. These advancements were achieved thanks to an interdisciplinary approach bridging electronics, chemistry, material science, mechanical engineering and medicine. In this complex knowledge blend, organic materials and organic electronics are increasingly proving to play a relevant role. Bioinert and biodegradable organic materials with favourable mechanical and chemical properties are key elements for a successful integration within the body tissues. While the ability of organic electronics to enable a mixed ionic and electronic charge transport is a win strategy for a proficient operation within physiologic medium. In this dissertation, advancements in this context are reported, approaching this wide field from different point of views: from the proposal for an inert system for chronic implantation, to the study of materials and devices for transient operation in the gastro intestinal tract. First, a proof-of-concept implantable device for the monitoring of the human bladder volume is proposed as a strategy to improve life quality of patients affected by neurogenic bladder and other lower urinary tract disorders. Its working principle is based on a capacitive linear encoder integrated with a passive wireless radio frequency resonator, which can be remotely interrogated. The system incorporates approved biocompatible materials, and its operation is tested in vitro. In order to simulate in-body condition the system signal transmissibility was tested through an ex vivo biological tissue and its operability was verified in contact with an extracellular medium. The sliding mechanism allows a wide sensing range without stringent requirements on materials properties and overall device stability, validating this encoding approach as a worthwhile alternative to stretchable devices proposed for the same therapeutic function. Afterwards, materials and devices candidates to be introduced in the context of edible electronics are proposed. Appropriate attention is posed in the selection of valuable materials for the design of active electronic components, electing only edible approved materials, or proceeding with a cytotoxicity assay on promising candidates, in order to provide a preliminary degree of biocompatibility. In particular, an n-type solid electrolyte gated transistor is proposed as a low-power device with good stability in aqueous environments. Effort was spent in understanding the charges accumulation mechanism at the semiconductor electrolyte interface and thus detecting the semiconductor permeability to ions. The characterization overtime shows a device shelf-life over 100 days without evident degradation. Moreover, preliminary tests demonstrate the possibility to fabricate devices fully degradable in water, hence mitigating possible device retention in the bowel after ingestion. These results represent a progress toward a fully transient and edible electronics, suitable to operate in the gastro intestinal tract.
L’area dell’ingegneria biomedicale che studia le interazioni tra le tecnologie elettroniche e il corpo umano sta acquisendo sempre più rilevanza e ormai da tempo ha rivoluzionato molti processi terapeutici e diagnostici. La progettazione di dispositivi medicali in grado di operare in stretto contatto con il corpo umano è di grande interesse, al fine di monitorare segnali biologici di natura elettrica o chimica, sostituire parti del corpo e ripristinare funzioni fisiologiche compromesse. È stato possibile raggiungere tali progressi grazie ad un approccio interdisciplinare che unisce: elettronica, chimica, ingegneria meccanica e medicina. In questa complessa miscela di conoscenze, i materiali organici e l’elettronica organica continuano a dimostrare la loro rilevanza. Da un lato, materiali bio-inerti e biodegradabili con convincenti proprietà chimiche e meccaniche sono elementi fondamentali per una corretta integrazione nel corpo umano, mentre la capacità dell'elettronica organica di consentire un trasporto misto di cariche ioniche ed elettroniche è una strategia vincente per un'operazione efficiente all'interno di mezzi fisiologici. In questa dissertazione vengono riportati alcuni progressi in questo ampio campo, dalla proposta di un sistema inerte per un impianto cronico, allo studio di materiali e dispositivi biodegradabili per applicazioni all’interno del tratto gastrointestinale. Nella prima parte, viene proposto un dimostratore di un dispositivo impiantabile per il monitoraggio del volume della vescica umana, come strategia per migliorare la qualità della vita di pazienti affetti da vescica neurologica e da altri disturbi del tratto urinario inferiore. Il suo principio di funzionamento si basa su un encoder lineare capacitivo, integrato in un risonatore passivo wireless a radiofrequenza, che può essere interrogato a distanza. Il sistema incorpora materiali biocompatibili approvati e il suo funzionamento viene testato in vitro. Al fine di simulare le condizioni il più possibile reali, la trasmissibilità del segnale è stata testata ex-vivo attraverso un tessuto biologico e la sua operabilità è stata verificata a contatto con un mezzo extracellulare. Il meccanismo a scorrimento consente di accomodare ampie deformazioni, senza requisiti rigorosi sulle proprietà meccaniche dei materiali e sulla stabilità complessiva del dispositivo, validando questo approccio di codifica come possibile alternativa ai dispositivi estensimetrici proposti per analoghe funzioni terapeutiche. Successivamente, vengono proposti materiali e dispositivi da introdurre nel contesto dell'elettronica commestibile. Un'adeguata attenzione viene posta nella selezione di materiali adatti per la progettazione di componenti elettronici attivi, scegliendo solo materiali commestibili approvati, o procedendo con test di citotossicità sui candidati promettenti, al fine di fornire un grado preliminare di biocompatibilità. In particolare, un transistore di tipo-n con gating elettrolitico solido viene proposto come dispositivo a bassa potenza con una buona stabilità in ambiente acquoso. In tale progetto, numerosi esperimenti sono stati eseguiti per comprendere il meccanismo di accumulo delle cariche all'interfaccia tra l’elettrolita e il semiconduttore e al fine di dimostrare la permeabilità del semiconduttore alle specie ioniche utilizzate. Una caratterizzazione del dispositivo prolungata nel tempo mostra una shelf-life che supera i 100 giorni, senza evidenti degradazioni. Inoltre, test preliminari dimostrano la possibilità di fabbricare dispositivi completamente degradabili in acqua, mitigando così la possibile ritenzione del dispositivo nell'intestino dopo l'ingestione. Questi risultati rappresentano un progresso verso un'elettronica completamente digeribile e commestibile, adatta ad operare nel tratto gastrointestinale.
Implantable and ingestible devices: new opportunities for electronics and human body interaction
Melloni, Filippo
2020/2021
Abstract
The area of Biomedical Engineering dealing with the interaction between electronic technologies and human body is increasingly gaining relevance and has long since revolutionized the process of doing therapy and diagnosis. The design of medical devices able to operate in an intense interaction with organs and tissues is particularly attractive. They are sophisticated tools capable to monitor electrical and chemical biological signals, replace parts of the body and restore compromised physiological functions. These advancements were achieved thanks to an interdisciplinary approach bridging electronics, chemistry, material science, mechanical engineering and medicine. In this complex knowledge blend, organic materials and organic electronics are increasingly proving to play a relevant role. Bioinert and biodegradable organic materials with favourable mechanical and chemical properties are key elements for a successful integration within the body tissues. While the ability of organic electronics to enable a mixed ionic and electronic charge transport is a win strategy for a proficient operation within physiologic medium. In this dissertation, advancements in this context are reported, approaching this wide field from different point of views: from the proposal for an inert system for chronic implantation, to the study of materials and devices for transient operation in the gastro intestinal tract. First, a proof-of-concept implantable device for the monitoring of the human bladder volume is proposed as a strategy to improve life quality of patients affected by neurogenic bladder and other lower urinary tract disorders. Its working principle is based on a capacitive linear encoder integrated with a passive wireless radio frequency resonator, which can be remotely interrogated. The system incorporates approved biocompatible materials, and its operation is tested in vitro. In order to simulate in-body condition the system signal transmissibility was tested through an ex vivo biological tissue and its operability was verified in contact with an extracellular medium. The sliding mechanism allows a wide sensing range without stringent requirements on materials properties and overall device stability, validating this encoding approach as a worthwhile alternative to stretchable devices proposed for the same therapeutic function. Afterwards, materials and devices candidates to be introduced in the context of edible electronics are proposed. Appropriate attention is posed in the selection of valuable materials for the design of active electronic components, electing only edible approved materials, or proceeding with a cytotoxicity assay on promising candidates, in order to provide a preliminary degree of biocompatibility. In particular, an n-type solid electrolyte gated transistor is proposed as a low-power device with good stability in aqueous environments. Effort was spent in understanding the charges accumulation mechanism at the semiconductor electrolyte interface and thus detecting the semiconductor permeability to ions. The characterization overtime shows a device shelf-life over 100 days without evident degradation. Moreover, preliminary tests demonstrate the possibility to fabricate devices fully degradable in water, hence mitigating possible device retention in the bowel after ingestion. These results represent a progress toward a fully transient and edible electronics, suitable to operate in the gastro intestinal tract.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/177121