Physics

The development of efficient and sustainable energy harvesting devices for miniaturized electronic devices has become increasingly significant in the industry 5.0 era. Among various potential materials, piezoelectric polymer-ceramic composites have emerged as a promising candidate for piezoelectric nanogenerators (PENGs) exploiting the synergistic effect of the high piezoelectric response of ceramic fillers and the flexibility and processing advantages of the polymer matrix. In this work, environmentally friendly PENGs based on Mn-doped (Bi 0.5 Na 0.5 )TiO 3 -BaTiO 3 (BNBTMn)/P(VDF-TrFE) microcomposites with different mass ratios of the ceramic inclusions were prepared using a facile solution casting route. These PENGs demonstrate simultaneously large output power, excellent sensitivity, and decent cyclability under various mechanical stimuli. In particular, the 3 wt% BNBTMn-loaded PENGs exhibit an output voltage of 52 V, a peak-to-peak short-circuit current of 12.8 µA, and an output power density of 25.9 μW/cm 2 under a cyclic impact load of 175 N at 5 Hz, outperforming almost all the piezoelectric microcomposites employing lead-free piezoelectric ceramic inclusions to date. The enhanced performance is attributed to improved interfacial polarization and local electric field concentration arising from the optimized dispersion of BNBTMn fillers within the polymer matrix. The output remains nearly unchanged after 15000 operating cycles of continuous impacts, suggesting excellent durability of our PENG. More intriguingly, the (BNBTMn)/P(VDF-TrFE) microcomposite-based PENG can capture the subtle movement of Adam’s apple (i.e. laryngeal prominence), unambiguously underpinning the viability of integrating them into wearable electronics as highly sensitive contact-mode throat vibration and motion sensors.

In order to utilise NiTi shape memory alloys in environments with extreme radiation, it is essential to understand how irradiation affects their superelastic properties on a nanoscale level. We use a spherical nanoindentation technique in two perpendicular directions, combined with indentation work analysis to evaluate the nanoscale superelastic behavior and functional degradation of Fe + ion irradiated NiTi. Cross-sectional nanoindentation reveals that the maximum hardening and the lowest superelastic response occur near the depth of peak Fe⁺ concentration (2.6–2.8 μm). Importantly, the superelastic behavior exhibits a non-monotonic dependence on damage level: complete loss of superelastic recovery is observed at 1.7 d.p.a., whereas partial recovery reappears at 8.5 d.p.a., indicating a competition between lattice amorphization and irradiation-mediated. Using cross-sectional nanoindentation, we can capture variations in stiffness and recoverable work at the nanoscale, as a function of depth, that cannot be resolved using conventional surface indentation methods. We conclude that ion irradiation leads to significant hardening and suppression of superelasticity phenomena due to inhibition of the stress-induced B2→B19′ martensitic transformation. These findings demonstrate that two-directional spherical nanoindentation is an effective approach for probing irradiation-induced functional gradients.