@article{snapp_cho_lee_haque_nam_park_2020, title={Tunable Piezoelectricity of Multifunctional Boron Nitride Nanotube/Poly(dimethylsiloxane) Stretchable Composites}, volume={32}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202004607}, abstractNote={Boron nitride nanotubes (BNNT) uniformly dispersed in stretchable materials, such as poly(dimethylsiloxane) (PDMS), could create the next generation of composites with augmented mechanical, thermal, and piezoelectric characteristics. This work reports tunable piezoelectricity of multifunctional BNNT/PDMS stretchable composites prepared via co‐solvent blending with tetrahydrofuran (THF) to disperse BNNTs in PDMS while avoiding sonication or functionalization. The resultant stretchable BNNT/PDMS composites demonstrate augmented Young's modulus (200% increase at 9 wt% BNNT) and thermal conductivity (120% increase at 9 wt% BNNT) without losing stretchability. Furthermore, BNNT/PDMS composites demonstrate piezoelectric responses that are linearly proportional to BNNT wt%, achieving a piezoelectric constant (|d33|) of 18 pmV−1 at 9 wt% BNNT without poling, which is competitive with commercial piezoelectric polymers. Uniquely, BNNT/PDMS accommodates tensile strains up to 60% without plastic deformation by aligning BNNTs, which enhances the composites’ piezoelectric response approximately five times. Finally, the combined stretchable and piezoelectric nature of the composite was exploited to produce a vibration sensor sensitive to low‐frequency (≈1 kHz) excitation. This is the first demonstration of multifunctional, stretchable BNNT/PDMS composites with enhanced mechanical strength and thermal conductivity and furthermore tunable piezoelectric response by varying BNNT wt% and applied strain, permitting applications in soft actuators and vibration sensors.}, number={43}, journal={ADVANCED MATERIALS}, author={Snapp, Peter and Cho, Chullhee and Lee, Dongwon and Haque, Md Farhadul and Nam, SungWoo and Park, Cheol}, year={2020}, month={Oct} }
 @article{lee_yuan_fay_chu_park_2019, title={Piezoelectric Characterization of Boron Nitride Nanotube-Polyurethane Composites}, volume={10982}, ISBN={["978-1-5106-2630-0"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2513999}, abstractNote={Boron nitride nanotubes (BNNTs) have exceptional thermal stability, thermal conductivity, mechanical properties, neutron radiation shielding, and piezoelectricity. Due to their multifunctional properties, BNNTs are potential candidates for sensory materials in harsh environments. Brittleness and non-conformity of conventional piezoelectric ceramics have limited their broad applications. Flexible and ultra-light piezoelectric sensors based on BNNTs could be an alternative solution in high temperature, high radiation, high shock, and severe vibration environments. In this study, BNNTPolyurethane (PU) composites were fabricated and their converse piezoelectric constant of d33 was assessed using a laser Doppler vibrometer (LDV). This study demonstrated that BNNT could be an excellent piezoelectric nanofiller for flexible sensor applications.}, journal={MICRO- AND NANOTECHNOLOGY SENSORS, SYSTEMS, AND APPLICATIONS XI}, author={Lee, Dongwon and Yuan, Fuh-Gwo and Fay, Catharine and Chu, Sang-Hyon and Park, Cheol}, year={2019} }