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Abstract The dielectric gap between the scanning probe microscopy (SPM) tip and the surface of a ferroelectric using conductive atomic force microscopy and piezoresponse force microscopy (PFM) is investigated. While the gap functions as a dielectric layer, it also allows tunneling current to inject charges into the ferroelectric when a critical loading force between 10–20 µN is applied to a tip with a radius of 25 nm under a bias voltage of 0.5 V. It is observed that the permittivity of the dielectric gap determines the coercive voltage measured by the piezoresponse hysteresis loop. While such studies done in air often produce coercive voltages much larger than those studied for the same materials in capacitor‐based studies, the use of high permittivity media such as water (ɛ_r= 79) or silicone oil (ɛ_r= 2.1‐2.8) produces coercive fields that more closely match those measured in conventional capacitor‐based polarization hysteresis loop measurements. Furthermore, using water as a dielectric medium in PFM imaging enhances the accuracy in extracting the amplitude and phase data from periodically poled lithium niobate crystals. These findings provide insight into the nanoscale phenomena of polarization switching instigated by the SPM tip and provide a pathway to improved quantitative studies. 

Abstract Recent advancements in wearable photonic sensors have marked a transformative era in healthcare, enabling non‐invasive, real‐time, portable, and personalized medical monitoring. These sensors leverage the unique properties of light toward high‐performance sensing in form factors optimized for real‐world use. Their ability to offer solutions to a broad spectrum of medical challenges – from routine health monitoring to managing chronic conditions, inspires a rapidly growing translational market. This review explores the design and development of wearable photonic sensors toward various healthcare applications. The photonic sensing strategies that power these technologies are first presented, alongside a discussion of the factors that define optimal use‐cases for each approach. The means by which these mechanisms are integrated into wearable formats are then discussed, with considerations toward material selection for comfort and functionality, component fabrication, and power management. Recent developments in the space are detailed, accounting for both physical and chemical stimuli detection through various non‐invasive biofluids. Finally, a comprehensive situational overview identifies critical challenges toward translation, alongside promising solutions. Associated future outlooks detail emerging trends and mechanisms that stand to enable the integration of these technologies into mainstream healthcare practice, toward advancing personalized medicine and improving patient outcomes. 

Abstract Mechanoresponsive polymeric materials that respond to mechanical deformation are highly valued for their potential in sensors, degradation studies, and optoelectronics. However, direct visualization and detection of these responses remain significant obstacles. In this study, novel mechanoresponsive polybiidenedionediyl (PBIT) derivative topochemical polymers are developed that depolymerize under mechanical forces, exhibiting a distinct and irreversible color change in response to grinding, milling, and compression. This color change is attributed to the alteration of polymer backbone conjugation during elongated Carbon‐Carbon (C─C) single bond cleavage. Quantum chemical pulling simulations on PBIT polymers reveals a force range of 4.3–5.0 nN associated with the selective cleavage of elongated C─C single bonds. This force range is comparable to that observed for typical homolytic mechanophores, supporting the mechanistic interpretation of homolytic bond scission under mechanical stress. C─C bond cleavage kinetic studies of PBIT under compression indicates that strong interchain interactions significantly increase the pressure needed to cleave the elongated C─C bonds. Additionally, PBIT polymer thin films are composited with polydimethylsiloxane to create free‐standing and robust thin films, which can serve as ink‐free and rewritable paper for writing and stress visualization applications. This advancement opens new possibilities for utilizing crystalline and brittle topochemical polymers in practical applications. 

Abstract Chalcogenide optical phase change materials (PCMs) have garnered significant interest for their growing applications in programmable photonics, optical analog computing, active metasurfaces, and beyond. Limited endurance or cycling lifetime is however increasingly becoming a bottleneck toward their practical deployment for these applications. To address this issue, a systematic study elucidating the cycling failure mechanisms of Ge₂Sb₂Se₄Te (GSST) is performed, a common optical PCM tailored for infrared photonic applications, in an electrothermal switching configuration commensurate with their applications in on‐chip photonic devices. Further a set of design rules building on insights into the failure mechanisms is proposed, and successfully implemented them to boost the endurance of the Ge₂Sb₂Se₄Te (GSST) device to over 67 000 cycles. 

Abstract We introduce the heterocumulene ligand [(Ad)NCC(^tBu)]⁻(Ad=1‐adamantyl (C₁₀H₁₅),^tBu=tert‐butyl, (C₄H₉)), which can adopt two forms, the azaalleneyl and ynamide. This ligand platform can undergo a reversible chelotropic shift using Brønsted acid‐base chemistry, which promotes an unprecedented spin‐state change of the [V^III] ion. These unique scaffolds are prepared via addition of 1‐adamantyl isonitrile (C≡NAd) across the alkylidyne in complexes [(BDI)V≡C^tBu(OTf)] (A) (BDI⁻=ArNC(CH₃)CHC(CH₃)NAr), Ar=2,6‐ⁱPr₂C₆H₃) and [(dBDI)V≡C^tBu(OEt₂)] (B) (dBDI²⁻=ArNC(CH₃)CHC(CH₂)NAr). ComplexAreacts with C≡NAd, to generate the high‐spin [V^III] complex with a κ¹‐N‐ynamide ligand, [(BDI)V{κ¹‐N‐(Ad)NCC(^tBu)}(OTf)] (1). Conversely,Breacts with C≡NAd to generate a low‐spin [V^III] diamagnetic complex having a chelated κ²‐C,N‐azaalleneyl ligand, [(dBDI)V{κ²‐N,C‐(Ad)NCC(^tBu)}] (2). Theoretical studies have been applied to better understand the mechanism of formation of2and the electronic reconfiguration upon structural rearrangement by the alteration of ligand denticity between1and2.