Weak voltage signals cannot be reliably measured using currently available logging tools when these tools are subject to high-temperature (up to 200 °C) environments for prolonged periods. In this paper, we present a digital lock-in amplifier (DLIA) capable of operating at temperatures of up to 200 °C. The DLIA contains a low-noise instrument amplifier and signal acquisition and the corresponding signal processing electronics. The high-temperature stability of the DLIA is achieved by designing system-in-package (SiP) and multi-chip module (MCM) components with low thermal resistances. An effective look-up-table (LUT) method was developed for the lock-in amplifier algorithm, to decrease the complexity of the calculations and generate less heat than the traditional way. The performance of the design was tested by determining the linearity, gain, Q value, and frequency characteristic of the DLIA between 25 and 200 °C. The maximal nonlinear error in the linearity of the DLIA working at 200 °C was about 1.736% when the equivalent input was a sine wave signal with an amplitude of between 94.8 and 1896.0 nV and a frequency of 800 kHz. The tests showed that the DLIA proposed could work effectively in high-temperature environments up to 200 °C.

Portable sensors with high selectivity and sensitivity are essential for ammonia detection. In this work, a colorimetric sensor based on non-close-packed photonic crystals (NPCs) was developed for visual monitoring of ammonia, which had great selectivity, stability, and durability. The initial structural color of the NPCs was customized in the entire color range by tuning the PMMA concentration and acrylamide (AM) content. Ethylene glycol-NPCs (EG-NPCs) with a softer texture were obtained by swelling of the NPCs in 5% glycerol & 30% ethylene glycol solution, and the reflective peak of the EG-NPCs with 50 mg mL⁻¹ AM shifted from 459 nm to 626 nm. Besides, the abundant hydroxyl groups in the EG-NPCs can form hydrogen bonds with ammonia, resulting in a greater decrease in the lattice distance. The reflective peak of the EG-NPCs blue shifted from 626 nm to 482 nm when the ammonia concentration increased from 0 μL cm⁻³ to 0.12 μL cm⁻³, and the δλ = 144 nm, which realized colorimetric sensing in the entire visible color range. The excellent selectivity, stability, and durability of the colorimetric sensors make it possible to sense ammonia in the air, which is critical for the safe production of chemical plants, farms, and other key sites.

Theoretical calculations and numerical simulations play a crucial role in analyzing material properties and devising effective research strategies. In this study, the photonic band gap (PBG) of polymethyl methacrylate (PMMA) and polystyrene (PS) photonic crystals was successfully predicted using theoretical calculations and numerical simulations. The agreement between the predicted results and the actual reflection peaks reached an impressive level of 99%. Utilizing SEM images, the prediction of reflection peaks in acrylamide (AM)—based photonic hydrogels was conducted using theoretical formulas and Rsoft 2019–Bandsolve software v2019.09. The relationship between the actual reflection peaks and compressive strains in AM-based photonic hydrogels featuring 251 nm PMMA PCs exhibited a remarkable similarity of over 96% with the theoretical and simulated results. In conclusion, an exploration was conducted into the relationship between reflection peaks and compressive strains for AM-based 270 nm PMMA photonic hydrogels, allowing the prediction of the actual reflection peaks under compression. The consistency observed between theoretical/simulated reflection peaks and actual reflection peaks validates the efficacy of this approach in evaluating the optical properties of photonic materials and predicting their responsive effects. This method offers a straightforward and expeditious solution for the design and fabrication of photonic materials.