Transdermal drug delivery (TDD) is widely used for painless dosing due to its minimally invasive nature compared to hypodermic needle injection and its avoidance of the gastrointestinal tract. However, the stratum corneum obstructs the permeation of drugs into skin. Microneedle and nanoneedle patches are ways to enhance this permeation. In this work, terahertz (THz) imaging is utilized to compare the efficacy of different TDD methods including topical application and via a needle patch. Our work shows the feasibility and potential of using THz imaging to quantify and evaluate different transdermal application methods.

In this research, we present the design, fabrication, and experimental validation of 3D printed bandpass filters and mux/demux elements for terahertz frequencies. The filters consist of a set of in-line polystyrene (PS) rectangular waveguides, separated by 100 µm, 200 µm, and 400 µm air gaps. The principle of operation for the proposed filters resides in coupled-mode theory. Q-factors of up to 3.4 are observed, and additionally, the experimental evidence demonstrates that the Q-factor of the filters can be improved by adding fiber elements to the design. Finally, using two independent THz broadband channels, we demonstrate the first mux/demux device based on 3D printed in-line filters for the THz range. This approach represents a fast, robust, and low-cost solution for the next generation of THz devices for communications.

Atomic-scale defects can control the exploitable optoelectronic performance of crystalline materials, and several point defects in diamond are emerging functional components for a range of quantum technologies. Nitrogen and hydrogen are common impurities incorporated into diamond, and there is a family of defects that includes both. The N₃VH⁰ defect is a lattice vacancy where three nearest neighbor carbon atoms are replaced with nitrogen atoms and a hydrogen is bonded to the remaining carbon. It is regularly observed in natural and high-temperature annealed synthetic diamond, and gives rise to prominent absorption features in the mid-infrared. Here, we combine time- and spectrally-resolved infrared absorption spectroscopy to yield unprecedented insight into the N₃VH⁰ defect’s vibrational dynamics following infrared excitation of the C–H stretch. In doing so, we gain fundamental information about the energies of quantized vibrational states, and corroborate our results with theory. We map out, for the first time, energy relaxation pathways, which include multiphonon relaxation processes and anharmonic coupling to the C–H bend mode. These advances provide new routes to quantify and probe atomic-scale defects.

Ferroelectric–paraelectric superlattices show emerging new states, such as polar vortices, through the interplay and different energy scales of various thermodynamic constraints. By introducing magnetic coupling at BiFeO₃–La_0.7Sr_0.3MnO₃ interfaces epitaxially grown on SrTiO₃ substrate, we find, for the first time in thin films, a sub-nanometer thick lamella-like BiFeO₃. The emergent phase is characterized by an arrangement of a two unit cell thick lamella-like structure featuring antiparallel polarization, resulting an antiferroelectric-like structure typically associated with a morphotropic phase transition. The antipolar phase is embedded within a nominal R3c structure and is independent of the BiFeO₃ thickness (4–30 unit cells). Moreover, the superlattice structure with the morphotropic phase demonstrates azimuth-independent second harmonic generation responses, indicating a change of overall symmetry mediated by a delicate spatial distribution of the emergent phase. This work enriches the understanding of a metastable state manipulated by thermodynamic constraints by lattice strain and magnetic coupling.