@article {47357,
	title = {Elastic piezoelectric aerogels from isotropic and directionally ice-templated cellulose nanocrystals: comparison of structure and energy harvesting},
	journal = {Cellulose},
	volume = {28},
	year = {2021},
	month = {JUL},
	pages = {6323-6337},
	type = {Article},
	abstract = {<p>We report the preparation of highly compressible and elastic piezoelectric aerogels of carboxylated cellulose nanocrystals (CNCs). Aqueous CNC dispersions containing polyethyleneimine and crosslinker were frozen isotropically to yield isotropic aerogels, while oriented aerogels were prepared by directional freezing. These aerogels were highly flexible and porous (similar to 85\% void fraction), exhibiting greater than 90\% recovery at 50\% compressive strain even after 100 compression-decompression cycles. Since such aerogels with low bulk modulus and high anisotropy would be an ideal platform for leveraging the piezoelectric properties of CNCs, we used them to prepare piezoelectric nanogenerator devices and determined their energy transduction behavior. Anisotropic aerogels led to an enhanced open-circuit voltage of 840 mV (at similar to 8 N applied force), which is over 2.6 times higher than isotropic aerogels (320 mV). The energy density of anisotropic aerogels was around 52 nW/cm(2), representing outstanding piezoelectric performance for cellulose-based aerogels. Such aerogels with high compressibility, elastic recovery and exceptional piezoelectric performance could have potential applications in sensors, wearable electronics, etc.</p>},
	keywords = {Aerogel, Anisotropic, Cellulose nanocrystals, energy harvesting, Piezoelectricity},
	issn = {0969-0239},
	doi = {10.1007/s10570-021-03896-6, Early Access Date = MAY 2021},
	author = {Ram, Farsa and Biswas, Bipul and Torris, Arun and Kumaraswamy, Guruswamy and Shanmuganathan, Kadhiravan}
}
@article {47353,
	title = {Highly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property},
	journal = {Ceramics International},
	volume = {47},
	year = {2021},
	month = {JUN },
	pages = {15750-15758},
	type = {Article},
	abstract = {<p>Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO3 (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt \%) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80\% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 ?W/cm2 (49.79 ?W/cm3) was obtained for PENG aerogels containing 83 wt\% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.</p>},
	keywords = {Ceramic polymer aerogels, energy harvesting, ice templating, piezoelectric},
	issn = {0272-8842},
	doi = {10.1016/j.ceramint.2021.02.147},
	author = {Ram, Farsa and Suresh, Karthika and Torris, Arun and Kumaraswamy, Guruswamy and Shanmuganathan, Kadhiravan}
}
