Increasing sensitivity, measuring points, and stability have always been the pursuit of sensors. ZnSe9:CO1 and Ag composite nano films were coated on polarization maintaining fiber (PMF). Then, the coated PMF was nested in capillary and hose which was encapsulated with polydimethylsiloxane (PDMS) and epoxy resin. The integrated capillary sensor and thermoplastic hose sensor were prepared. The gradient sensitization of various measurement parameters such as temperature, stress, and micro bending is realized. The temperature sensitivity is 1.49 nm/°C, the micro bending sensitivity is 1.72 nm/102 g, and the stress sensitivity is 6.27 nm/mε. The sensors maintain good linearity and instantaneous response while having high sensitivity. By adjusting the length of PMF, the number of troughs is increased in the same band range, and different troughs have different sensitivities, which solves the inherent problem of cross sensitivity and realizes multiparameter measurement. Capillary sensors are used for remote safe real-time monitoring of mechanical overheating, and hose sensors are used for real-time monitoring of bridge load and human joint bending. This work is of great significance to the extension of the application range of optical fiber sensor.

In this work, the surface of long-period fiber grating (LPFG) and polarization maintaining fiber (PMF) is functionalized based on the interaction between the resonance wavelength and external environment. LPFG coated with a 150 nm ZnSe/Co film is fixed on a hollow bracket, prestressed, and annealed many times. A highly sensitive liquid level sensor with adjustable sensitivity, an adjustable measurement range, and a high liquid level early warning is prepared. The waveguide layer controlled by humidity is constructed by filling poly­(3,4-ethylenedioxythiophene)/poly­(styrene sulfonate) (PEDOT/PSS) in a periodically etched PMF. The surface is coated with a poly­(vinyl alcohol) (PVA) and carbon nanotube (CNT) composite polymer. After laser processing, a honeycomb porous film is obtained, and the humidity sensor with wavelength modulation is prepared. The pH-sensitive polymer is successively adsorbed on the surface of PMF coated with a 120 nm indium tin oxide (ITO) film by electrostatic self-assembly (ESA). Poly­(allylamine hydrochloride) (PAH), poly­(acrylic acid) (PAA), and poly­(styrene sulfonate) (PSS) constitute a composite film with rapid deposition and high permeability that is covered with polyaniline/poly­(methyl methacrylate) (PMMA) as the protective layer. After laser processing, a fluffy porous film structure is formed. The pH sensor is obtained and the preparation steps are greatly reduced. Finally, based on the wavelength division multiplexing (WDM) and multiwavelength matrix (MWM), the problem of crosstalk is solved. An integrated sensor is constructed to realize the simultaneous measurement of temperature, liquid level, humidity, and pH. It has been successfully applied to monitor the overall environment of a chemical waste liquid storage tank. The sensor has the advantages of remote monitoring, safety, efficiency, and labor-saving.

The rapid, portable, and in situ measurement of the ascorbic acid (AA) solution remains a challenge, and there is no suitable way to achieve multiscale regulation of the measurement range and sensitivity. In this work, water-soluble CdTe, CdTe/ CdSe, and CdTe/CdSe/ZnS quantum dots (QDs) were used as fluorescence probes (FPs), and the specific sensitivity of photoluminescence (PL) intensity and AA were used as a detection indicator. By changing the concentration of the FP and the type of core−shell structure, multiscale regulation of the measurement range and sensitivity was realized. The same FP with distinct sensitivity in different measurement ranges is ingeniously realized by double-layer core−shell CdTe/CdSe/ZnS with type II-I band gap transition, which greatly expanded the application fields. The maximum measurement range was 0−27 μM and the minimum detection limit was 0.014 μM for three FP systems. The capillary sensor with a honeycomb QD film attached to the inner wall was prepared by drying at room temperature, high-temperature heating, and laser processing, which greatly increased the contact area between the QDs and AA and reduced the measurement time. Furthermore, the microfluidic system was used to precisely control the deposition area and position of the film, the concentration of the FP was adjusted and the deposition status of the film was observed in real time, so as to achieve real-time in situ rapid detection of the four concentration orders of the AA solution. This work is of great significance for the rapid, portable, multifield, and in situ real-time detection in the field of biomolecule detection.

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