Piezoelectric Nanoparticle–Polymer Composite Foams

Piezoelectric polymer composite foams are synthesized using different sugar-templating strategies. By incorporating sugar grains directly into polydimethylsiloxane mixtures containing barium titanate nanoparticles and carbon nanotubes, followed by removal of the sugar after polymer curing, highly compliant materials with excellent piezoelectric properties can be fabricated. Porosities and elasticity are tuned by simply adjusting the sugar/polymer mass ratio which gave an upper bound on the porosity of 73% and a lower bound on the elastic coefficient of 32 kPa. The electrical performance of the foams showed a direct relationship between porosity and the piezoelectric outputs, giving piezoelectric coefficient values of ∼112 pC/N and a power output of ∼18 mW/cm³ under a load of 10 N for the highest porosity samples. These novel materials should find exciting use in a variety of applications including energy scavenging platforms, biosensors, and acoustic actuators

3D Optical Printing of Piezoelectric Nanoparticle–Polymer Composite Materials

Here we demonstrate that efficient piezoelectric nanoparticle–polymer composite materials can be optically printed into three-dimensional (3D) microstructures using digital projection printing. Piezoelectric polymers were fabricated by incorporating barium titanate (BaTiO₃, BTO) nanoparticles into photoliable polymer solutions such as polyethylene glycol diacrylate and exposing to digital optical masks that could be dynamically altered to generate user-defined 3D microstructures. To enhance the mechanical-to-electrical conversion efficiency of the composites, the BTO nanoparticles were chemically modified with acrylate surface groups, which formed direct covalent linkages with the polymer matrix under light exposure. The composites with a 10% mass loading of the chemically modified BTO nanoparticles showed piezoelectric coefficients (<i>d</i>₃₃) of ∼40 pC/N, which were over 10 times larger than composites synthesized with unmodified BTO nanoparticles and over 2 times larger than composites containing unmodified BTO nanoparticles and carbon nanotubes to boost mechanical stress transfer efficiencies. These results not only provide a tool for fabricating 3D piezoelectric polymers but lay the groundwork for creating highly efficient piezoelectric polymer materials <i>via</i> nanointerfacial tuning

Tunable Surface and Matrix Chemistries in Optically Printed (0–3) Piezoelectric Nanocomposites

In this work, the impacts of varying surface modification, matrix parameters, and fabrication conditions on the performance of optically printed (0–3) piezoelectric polymer nanocomposites are examined. For example, we find that a 75% reduction in nanoparticle edge-length boosted the piezoelectric coefficient (<i>d</i>₃₃) by over 100%. By optimizing the composition and fabrication conditions, 10% by mass loading barium titanate nanocomposites are able to yield <i>d</i>₃₃ values of ∼80 pC/N compared to <5 pC/N when parameters are not optimized. With a more complete understanding of how to enhance the performance of (0–3) piezoelectric polymer nanocomposites, these materials should find use in a wide range of applications

Nanofiber Near-Field Light–Matter Interactions for Enhanced Detection of Molecular Level Displacements and Dynamics

We experimentally demonstrate that plasmonic nanoparticles embedded in the evanescent field of subwavelength optical waveguides (WGs) are highly sensitive to distances normal to the propagation of light, showing an ∼10× increase in spatial resolution compared to the optical field decay of the WG. The scattering cross-section of the Au nanoparticle is increased by the plasmon–dielectric coupling interaction when the nanoparticle is placed near the dielectric surface of the WG, and the decay of the scattering signal is enhanced, showing angstrom level distance sensitivity within 10 nm from the WG. Numerical studies with the finite-difference time-domain (FDTD) method correlate well with the experimental results. To demonstrate real-time monitoring of a single molecule stretching in the evanescent field, we linked individual single-stranded DNA molecules between the WG and plasmonic nanoparticles and pushed on the nanoparticles with fluidic forces. The simple design and ease of obtaining optical feedback on molecular displacements makes our approach ideal for new in situ force sensing devices, imaging technologies, and high-throughput molecular analysis