Deepam Maurya

The transition of autonomous vehicles into fleets requires an advanced control system design that relies on continuous feedback from the tires. Smart tires enable continuous monitoring of dynamic parameters by combining strain sensing with traditional tire functions. Here, we provide breakthrough in this direction by demonstrating tire-integrated system that combines direct mask-less 3D printed strain gauges, flexible piezoelectric energy harvester for powering the sensors and secure wireless data transfer electronics, and machine learning for predictive data analysis. Ink of graphene based material was designed to directly print strain sensor for measuring tire-road interactions under varying driving speeds, normal load, and tire pressure. A secure wireless data transfer hardware powered by a piezoelectric patch is implemented to demonstrate self-powered sensing and wireless communication capability. Combined, this study significantly advances the design and fabrication of cost-effective smart tires by demonstrating practical self-powered wireless strain sensing capability.

The desire for multifunctional devices has driven significant research toward exploring multiferroics, where the coupling between electric, magnetic, optical, and structural order parameters can provide new functionality. While BiFeO₃ is a well studied multiferroic, recent research has shown that the addition of BaTiO₃ can improve the material properties. In this study, we perform time resolved differential reflectivity measurements of (1 − x)BaTiO₃–(x)BiFeO₃, with x = 0.725 epitaxial films grown on a lanthanum strontium manganite (LSMO) layer with a strontium titanate (STO) substrate, and BaTiO₃–BiFeO₃ nano-rods grown on Pt/Si. Our time resolved measurements can be used to probe dynamical properties on picosecond time scales. Information obtained is vital towards the design and understanding of high speed devices that incorporate multiferroic materials. We find that the contribution to the transient reflectivity response of a BaTiO₃–BiFeO₃ film due to carrier dynamics can be quantitatively explained by the diffusion of the photoexcited carriers away from the surface and that the ambipolar diffusion constant is below 1–2 cm² s⁻¹. At low temperature and for thicker films, in addition to a response from carrier dynamics, we also observed oscillations in the transient reflectivity with periods of 30–37 ps. We attribute these oscillations to propagating coherent acoustic phonons in the films. In the BaTiO₃–BiFeO₃ nano-rods samples only, we observed an additional oscillation with frequency in the range of 8 GHz. This is close to a theoretically predicted magnon frequency, but the strength of this oscillation only had a very weak magnetic field dependence. Another explanation for this feature could be multiple reflections of the acoustic phonons at the Pt interfaces (due to the large acoustic impedance mismatch).

Piezoelectric coefficients are constrained by the intrinsic crystal structure of the constituent material. Here we describe design and manufacturing routes to previously inaccessible classes of piezoelectric materials that have arbitrary piezoelectric coefficient tensors. Our scheme is based on the manipulation of electric displacement maps from families of structural cell patterns. We implement our designs by additively manufacturing free-form, perovskite-based piezoelectric nanocomposites with complex three-dimensional architectures. The resulting voltage response of the activated piezoelectric metamaterials at a given mode can be selectively suppressed, reversed or enhanced with applied stress. Additionally, these electromechanical metamaterials achieve high specific piezoelectric constants and tailorable flexibility using only a fraction of their parent materials. This strategy may be applied to create the next generation of intelligent infrastructure, able to perform a variety of structural and functional tasks, including simultaneous impact absorption and monitoring, three-dimensional pressure mapping and directionality detection.

In this study, we investigate the changes occurring in the microstructure and thermoelectric properties of PbTe0.9S0.1 alloy (PbTe–PbS) under varying thermal treatment conditions. Transmission electron microscopy (TEM) studies were utilized to reveal the distribution of nano-precipitates in the annealed alloy. PbTe0.9S0.1 alloy with PbS phase precipitates displayed a significant reduction in the thermal conductivity and an enhancement in the Seebeck coefficient. The 47% reduction in lattice thermal conductivity at the measurement temperature of 300°C in the alloy annealed at 400°C was attributed to the phonon scattering occurring due to the presence of nano-precipitates. The annealed alloy displayed higher electrical conductivity at room temperature than that of the alloy without annealing. The maximum figure of merit, ZT, was found to be 0.76 at 300°C in the alloy annealed at 400°C.

We optically study the as-yet little explored multiferroic material, BaTiO3-BiFeO3 (BTO-BFO), that has demonstrated enhanced magnetic properties, a higher DC resistance in comparison to BFO, and improved magnetoelectric coupling. Our studies include: ultrafast time resolved differential reflection, optically induced birefringence, and second-harmonic nano-imaging of the ferroic order. We observe a strong sensitivity to pump/probe polarizations, photo-induced ferroelectric poling on a picosecond timescale, as well as the generation of photo-induced coherent acoustic phonons with a frequency of ∼11 GHz. The second-harmonic generation nano-imaging reveals disordered but distinct ferroelectric domain order, percolating even across grain boundaries in the poly-crystalline thin film.

We report correlation between the electro-mechanical, ferroelectric, optical and opto-electric behavior in Pb(Zn1/3Nb2/3)O3–Pb0.97La0.03(Zr,Ti)O3 transparent ceramics. Optical interaction during current–voltage (I–V) measurements enhanced the current output and revealed its strong dependence on wavelength and power of the impinging radiation. Piezoresponse force microscopy revealed that the improved characteristics at low stoichiometric excess of various elements were related to nano-sized stripe domains. Raman analysis indicated the presence of short-range clusters with rhombohedral–tetragonal phase distributed at much above the Curie temperature. The results reveal the potential of these ceramics in wireless opto-electric devices operating over a wide-range of wavelengths and temperatures. These classes of ceramics have successfully demonstrated in literature for use in pyroelectric generators and UV light energy harvesting, piezoelectric transformers.

In this study, we investigate the changes occurring in the microstructure and thermoelectric properties of PbTe0.9S0.1 alloy (PbTe–PbS) under varying thermal treatment conditions. Transmission electron microscopy (TEM) studies were utilized to reveal the distribution of nano-precipitates in the annealed alloy. PbTe0.9S0.1 alloy with PbS phase precipitates displayed a significant reduction in the thermal conductivity and an enhancement in the Seebeck coefficient. The 47% reduction in lattice thermal conductivity at the measurement temperature of 300°C in the alloy annealed at 400°C was attributed to the phonon scattering occurring due to the presence of nano-precipitates. The annealed alloy displayed higher electrical conductivity at room temperature than that of the alloy without annealing. The maximum figure of merit, ZT, was found to be 0.76 at 300°C in the alloy annealed at 400°C.