3D printing of renewable materials such as cellulose nanofibrils (CNFs) offers an attractive pathway for fabricating sustainable materials while concomitantly being able to replace existing petroleum-based polymeric materials. CNFs, known as nano-structured cellulose with higher aspect ratio than cellulose fibers, have attracted significant interest because of low cost, biocompatibility, bioactivity, nontoxicity, biodegradability, and oxygen barrier properties, which give them numerous potential applications such as drug delivery, tissue engineering, food packaging, etc. Recently, a strategic combination of stimuli-responsive polymers and nanomaterial fillers for enhanced smart functionality has attracted increasing interest. We have successfully synthesized thermo-responsive PNIPAM/CNF hydrogels with reversible and tunable transparency. A hybrid PNIPAm/CNF hydrogel material as a 3D printing ink was developed for patterning of 3D objects. The 3D printed PNIPAm/CNF hydrogel objects exhibit tunable optical properties as a function of temperature and are capable of filtering wavelength bandpass selectivity as verified by PROBE Spectroscopy. The mechanism of PNIPAm/CNF transparency change was verified by the micro/nano structures of the PNIPAM/CNF hydrogel films dried below and above the LCST. Below LCST, PNIPAM/CNF hydrogel films exhibit transparency or semi-transparency due to the uniform hydrogen bonding between hydrophilic PNIPAM, CNF, and water. Above the LCST, PNIPAM becomes dehydrated due to conformation changes arising from the repulsion of water and CNF, thus initiating phase separation to generate micro/nanoparticles. Consequently, these nano/microparticles result in light scattering effects and hence opacity. Our results will overview how optical transition occurs and applications in 3D printing.<br/>

Thermo-responsivity and tunable optics of a PNIPAM/cellulose nanofibrillar hydrogel for 3D printing

2019 Spring National Meeting

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