Highly Efficient Triplet–Triplet Annihilation Upconversion in Polycaprolactone: Application to 3D Printable Architecture and Microneedles

This research reports the next generation of solid-state triplet–triplet annihilation upconversion (TTA-UC) host material (polycaprolactone, PCL) for highly efficient, processable, and biocompatible solid-state TTA-UC. UC PCL was successfully fabricated using...

Acridine Based Small Molecular Hole Transport Type Materials for Phosphorescent OLED Application

Two small molecular hole-transporting type materials, namely 4-(9,9-dimethylacridin-10(9H)-yl)-N-(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)-N-phenylaniline (TPA-2ACR) and 10,10′-(9-phenyl-9H-carbazole-3,6-diyl)bis(9,9-dimethyl-9,10-dihydroacridine) (PhCAR-2ACR), were designed and synthesized using a single-step Buchwald–Hartwig amination between the dimethyl acridine and triphenylamine or carbazole moieties. Both materials showed high thermal decomposition temperatures of 402 and 422 °C at 5% weight reduction for PhCAR-2ACR and TPA-2ACR, respectively. TPA-2ACR as hole-transporting material exhibited excellent current, power, and external quantum efficiencies of 55.74 cd/A, 29.28 lm/W and 21.59%, respectively. The achieved device efficiencies are much better than that of the referenced similar, 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC)-based device (32.53 cd/A, 18.58 lm/W and 10.6%). Moreover, phenyl carbazole-based PhCAR-2ACR showed good device characteristics when applied for host material in phosphorescent OLEDs.

Exploring mechanical assonance for impact energy harvesting using acoustic metamaterials

Acoustic metamaterials are engineered to possess unique dynamic properties that are not commonly found in nature. It has been demonstrated that customizing the characteristics of their local features can help optimize their dynamic performance under specific loading conditions. Drawing inspiration from the literary device called “assonance,” the term “mechanical assonance” may be ascribed to the dynamic phenomenon realized by sequencing oscillators with tuned responses within a waveguide to engineer a prescribed wave transformation across it. In this context, assonance provides a framework to utilize resonant local features within a host structure or material and interactive mechanisms thereof as building blocks to create enriched functionalities for acoustic metamaterials. Using a discrete element representation for an acoustic metamaterial barrier (AMB), a numerical study is conducted to ascertain parametric dependence for assonant mechanisms related to resonator frequencies, their sequencing, and host material stiffness. Normalized metrics are extracted to estimate transmitted pulse mitigation under impact-type loading. It is found that resonator sets with octave spacing having the number of resonators of a specific frequency proportional to that frequency’s amplitude in the input spectrum is desirable for lower transmissibility. Further, sequencing the lowest frequency resonator set closest to the incident-side gives better performance. Engineering a high degree of impedance mismatch between host material sections is also preferable. The energy sequestered by the local resonators can be harvested utilizing the resonator’s mass as the multifunctional kernel for a linear electromagnetic generator. A multiphysical model is developed to predict the harvested electric voltage and power from the AMB and validated using proof-of-concept experiments. Finally, various coil placement and voltage rectification schemes are also studied using simulations to ascertain preferable design configurations.