This thesis presents the design and fabrication of stimuli-responsive hydrogel particles, achieved through a 3D printed microfluidics-based approach. Poly(N- isopropylacrylamide) (PNIPAM) is one of the most widely studied thermo-responsive hydrogels bringing significant attention to the researchers. This is due to PNIPAM ability to undergo reversible changes in volume and phase transition from hydrophilic to hydrophobic in response to temperature variations below and above lower critical temperature solution (LCST ~ 32 oC). However, controlling the swelling ratio and mechanical properties of these microgels remains a challenge, limiting their utility in biomedical applications such as controlled drug delivery systems. In this study, a microfluidics method was employed to precisely generate monodisperse and spherical thermo-responsive PNIPAM microgels. By manipulating flow rates, channel dimensions, and composition of precursor solutions (monomer, crosslinker, and photo-initiator) within flow-focusing microfluidic channels, PNIPAM hydrogel particles with tailored sizes (around 80 micrometers) were produced. the morphology of theses fabricated microgels were examined using confocal laser scanning microscope (CLSM) for imaging. Swelling and mechanical behaviour of the fabricated microgels were systematically characterized under different temperature conditions by using oscillation temperature ramp and oscillation frequency sweep on rheological tests ensuring the responsiveness, reversibility, and stability of the hydrogel particles. The impact of microgels composition including silica nanoparticles (NPs) and microfluidic designing parameters on the final particle properties was investigated. The incorporation of silica NPs within PNIPAM microgels allowed for the control of the swelling ratio from 4 to 0.2 and improved the storage and loss modulus by 10 times. The developed PNIPAM microgels incorporating silica NPs exhibited tuneable swelling behaviour and mechanical properties, making them suitable for controlled drug delivery and tissue engineering. This research contributed to advancing the design and fabrication of functional hydrogel particles with tailored properties, opening new avenues for the development of innovative smart materials. Keywords: Thermo-responsive hydrogels, PNIPAM microgels, microfluidics, swelling ratio, mechanical properties
Questa tesi descrive il design e la fabbricazione di particelle di idrogel responsive alle variazioni di temperatura, ottenute attraverso un approccio basato sulla microfluidica. Il poli(N-isopropilacrilammide) (PNIPAM) è uno dei polimeri più ampiamente utilizzati nello sviluppo di idrogel termo-sensibili, grazie alla sua capacità di subire cambiamenti di volume reversibili e transizione di fase da idrofilo a idrofobo in risposta alle variazioni di temperatura al di sotto e al di sopra della temperatura critica inferiore della soluzione (LCST ~ 32 °C). Tuttavia, controllare le proprietà meccaniche e di rigonfiamento di questi microgel rimane una sfida, limitando la loro utilità in applicazioni biomediche come i sistemi di rilascio controllato di farmaci. In questo studio, è stato impiegato un metodo di microfluidica per generare con precisione i microgel termo-sensibili monodispersi e sferici. Manipolando i flussi, le dimensioni dei canali e la composizione delle soluzioni precursorie (monomero, reticolante e foto-iniziatore) all'interno dei canali microfluidici a flusso focalizzato, sono stati sintetizzati particelle di idrogel PNIPAM con dimensioni su misura intorno a 80 micrometri e strutture interne controllate, che sono state poi esaminate utilizzando un microscopio confocale a scansione laser (CLSM). Il comportamento di rigonfiamento e le proprietà meccaniche dei microgel sintetizzati sono stati caratterizzati sistematicamente in diverse condizioni di temperatura utilizzando test reologici a oscillazione per garantire la responsività, reversibilità e stabilità delle particelle di idrogel. È stata investigata l'impatto della composizione dell'idrogel inclusi nanoparticelle di silice e i parametri progettuali della microfluidica sulle proprietà finali delle particelle. L'incorporazione delle nanoparticelle di silice all'interno dei microgel PNIPAM ha permesso il controllo del rapporto di rigonfiamento da 4 a 0,2 e ha migliorato il modulo elastico e viscoso di 10 volte. I microgel PNIPAM sviluppati, incorporando nanoparticelle di silice, mostrano un comportamento di rigonfiamento e proprietà meccaniche modulabili, rendendoli adatti per sistemi di rilascio controllato di farmaci. Questa ricerca ha contribuito ad avanzare il design e la fabbricazione di particelle funzionali di idrogel con proprietà su misura, aprendo nuove vie per lo sviluppo di materiali intelligenti innovativi.
Design and fabrication of thermo-responsive hydrogel particles with tunable swelling and mechanical behavior via microfluidics method
Rahmanizadeh, Mohammadreza
2022/2023
Abstract
This thesis presents the design and fabrication of stimuli-responsive hydrogel particles, achieved through a 3D printed microfluidics-based approach. Poly(N- isopropylacrylamide) (PNIPAM) is one of the most widely studied thermo-responsive hydrogels bringing significant attention to the researchers. This is due to PNIPAM ability to undergo reversible changes in volume and phase transition from hydrophilic to hydrophobic in response to temperature variations below and above lower critical temperature solution (LCST ~ 32 oC). However, controlling the swelling ratio and mechanical properties of these microgels remains a challenge, limiting their utility in biomedical applications such as controlled drug delivery systems. In this study, a microfluidics method was employed to precisely generate monodisperse and spherical thermo-responsive PNIPAM microgels. By manipulating flow rates, channel dimensions, and composition of precursor solutions (monomer, crosslinker, and photo-initiator) within flow-focusing microfluidic channels, PNIPAM hydrogel particles with tailored sizes (around 80 micrometers) were produced. the morphology of theses fabricated microgels were examined using confocal laser scanning microscope (CLSM) for imaging. Swelling and mechanical behaviour of the fabricated microgels were systematically characterized under different temperature conditions by using oscillation temperature ramp and oscillation frequency sweep on rheological tests ensuring the responsiveness, reversibility, and stability of the hydrogel particles. The impact of microgels composition including silica nanoparticles (NPs) and microfluidic designing parameters on the final particle properties was investigated. The incorporation of silica NPs within PNIPAM microgels allowed for the control of the swelling ratio from 4 to 0.2 and improved the storage and loss modulus by 10 times. The developed PNIPAM microgels incorporating silica NPs exhibited tuneable swelling behaviour and mechanical properties, making them suitable for controlled drug delivery and tissue engineering. This research contributed to advancing the design and fabrication of functional hydrogel particles with tailored properties, opening new avenues for the development of innovative smart materials. Keywords: Thermo-responsive hydrogels, PNIPAM microgels, microfluidics, swelling ratio, mechanical propertiesFile | Dimensione | Formato | |
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2024_04_Mohammadreza_Rahmanizadeh.pdf
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2024_04_Mohammadreza_Rahmanizadeh_ExecutiveSummary.pdf
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https://hdl.handle.net/10589/219778