Nanomanufacturing

This paper focuses on the X-cut Y-propagating lithium niobate Mach–Zehnder modulator and studies how its performance degrades under atmospheric neutron irradiation. Since SRIM cannot directly simulate neutron-induced nuclear reactions, 1 MeV H⁺ ions are adopted as surrogate particles to compute displacement damage. SRIM is used to simulate the interaction between equivalent particles and lithium niobate lattices, constructing a material damage model that links neutron fluence to defect density, electro-optic coefficient degradation, and increased transmission loss. These material degradation relations are imported into COMSOL Multiphysics to build a multiphysics-coupled model integrating radiation damage, optical-field transmission, and electric-field modulation. Material-level simulation outputs are mapped onto three-dimensional real devices via structural equivalence principles. The simulation results show that lattice defect density rises with increasing neutron fluence, which further induces half-wave voltage drift, elevated insertion loss, and continuous extinction-ratio reduction. This work reveals the neutron displacement-damage-driven performance degradation mechanism and establishes a complete simulation workflow: neutron fluence → lattice defects → material property deterioration → device performance degradation. The established framework supports radiation-hardened design and on-orbit lifetime assessment for lithium-niobate-based space photonic devices. Limitations of the surrogate-particle approximation and model boundaries are also discussed, as all quantitative trends are simulation-derived rather than fully validated by experimental measurement.

Polypyrrole (PPy) nanofilms were deposited by in situ chemical oxidative polymerization on polyethylene or polypropylene. The thickness is determined by SEM of the cross-section. Thin thickness nanofilms (180 ± 5 nm) are deposited. The nanofilms are then modified by nucleophilic addition to attach functional groups to the nanofilms. Strong nucleophiles (e.g., thiols) react by conventional heating. Weak nucleophiles (e.g., nitroanilines) only react when applying microwaves. The spectroscopic (UV–visible, FTIR, XPS and XANES) characterization shows the attachment of functional groups and the change in electronic properties upon the reaction. The conductivity of the functionalized PPy nanofilms are lower than unmodified PPy nanofilms, likely due to steric effects on the extended conjugation and disturbance of the electron hopping between chains. While reaction with some nucleophiles (e.g., bisulfite ion) makes nanofilms more hydrophilic, modification with long alkyl chains or fluorinated long chains produces highly hydrophobic nanofilms. No noticeable effect of the reaction on the film thickness is observed, suggesting little or no loss of polymer due to dissolution.

A low-voltage alternating current (AC) field (20 V peak-to-peak, 1 kHz) was superimposed on a conventional direct current (DC) electrospinning configuration in order to test whether the shape of that perturbation measurably alters fiber formation. A function generator delivered sinusoidal, pulsed (square), ramp and arbitrary (noise) waveforms to a foil-covered flat collector, while a standard DC high-voltage source (20 kV) drove the jet from the spinneret. Polyvinylpyrrolidone (PVP) nanofibers were characterized by scanning electron microscopy (SEM), fiber-diameter distribution analysis (FIJI/ImageJ), quantitative orientation analysis and contact profilometry. One-way analysis of variance across the six conditions was significant (F(5.594) = 5.56, p = 5.1 × 10⁻⁵) but the associated effect size was small (η² = 0.045). Relative to the connected control (237 ± 52 nm), the ramp (205.5 ± 43.9 nm), noise (201.3 ± 48.6 nm) and pulse (212.6 ± 70.0 nm) waveforms yielded significantly finer fibers (Tukey HSD, p = 0.0008, 0.0001 and 0.022, respectively); relative to the grounded control (215 ± 47 nm), no waveform reached significance. The ramp waveform produced the narrowest diameter distribution but, unexpectedly, the roughest mat of the four AC conditions (Ra = 1.95 µm against 0.74 µm for the grounded control), while the noise waveform gave both the smallest mean diameter and the smoothest mat (Ra = 0.61 µm); with a single profile per scan direction, these roughness values are descriptive rather than statistically compared. Quantitative orientation analysis using two independent estimators (structure tensor and fast Fourier transform) returned Herman orientation factors of S ≤ 0.13 for every condition, against S = 0.81 for a partially aligned reference population: no condition exceeded the isotropic noise floor of the FFT estimator (S95 = 0.141), and the three conditions that marginally exceeded the structure-tensor floor (S95 = 0.104) included the connected control, which received no oscillating signal. No waveform, including the pulsed waveform, produced fiber alignment attributable to the AC field. The applied AC amplitude corresponds to approximately 0.05% of the DC voltage, and the associated oscillating field (±50 V m⁻¹) is approximately three orders of magnitude smaller than the mean DC field (~1 × 10⁵ V m⁻¹); the electrohydrodynamic mechanisms discussed here are therefore presented as hypotheses requiring direct measurement rather than as established explanations. Within these limits, low-voltage waveform modulation is a simple, safe and retrofittable route to modest control of nanofiber diameter and mat uniformity in a single-polymer system, but it does not induce fiber alignment.