Simultaneous measurement of the BOD concentration and temperature based on a tapered microfiber for water pollution monitoring

Microbial Biosensors for Rapid Determination of Biochemical Oxygen Demand: Approaches, Tendencies and Development Prospects

One of the main indices of the quality of water is the biochemical oxygen demand (BOD). A little over 40 years have passed since the practical application of the first microbial sensor for the determination of BOD, presented by the Japanese professor Isao Karube. This time span has brought new knowledge to and practical developments in the use of a wide range of microbial cells based on BOD biosensors. At present, this field of biotechnology is becoming an independent discipline. The traditional BOD analysis (BOD₅) has not changed over many years; it takes no less than 5 days to carry out. Microbial biosensors can be used as an alternative technique for assessing the BOD attract attention because they can reduce hundredfold the time required to measure it. The review examines the experience of the creation and practical application of BOD biosensors accumulated by the international community. Special attention is paid to the use of multiple cell immobilization methods, signal registration techniques, mediators and cell consortia contained in the bioreceptor. We consider the use of nanomaterials in the modification of analytical devices developed for BOD evaluation and discuss the prospects of developing new practically important biosensor models.

Two-photon direct laser writing of micro Fabry-Perot cavity on single-mode fiber for refractive index sensing

Using the two-photon polymerization (TPP) lithography, here we propose and experimentally demonstrate a fiber-tipped Fabry-Perot interferometer (FPI) for liquid refractive index (RI) measurement. To fit the aqueous environment, the FPI is designed as an open-cell microstructure consisting of well-crafted surfaces together with supporting rods, where the major spectral interference occurs between the waveguide's facet and the printed surface. Subsequently, the sensing performances of the fiber FPI are comprehensively studied under various RI as well as temperature configurations. The RI sensitivity is obtained to be ∼1058 nm/RIU with a low detection limit of 4.5× 10^-6 RIU, which is comparable to that of previous reported FPIs. And the temperature cross-sensitivity reaches a value of 8.2 × 10^-5 RIU/°C, indicating the good reliability for RI monitoring. Compared to other fiber FPIs, our sensor exhibits substantial advantages such as ease of fabrication, highly smooth cavity surfaces, and sufficient mechanical strength, providing a practical and competitive solution for chemical and biological sensing.

A Plus Shaped Cavity in Optical Fiber Based Refractive Index Sensor

The optical fiber grating sensors have strong potential for the detection of biological samples. However, a careful effort is still in demand to enhance the performance of existing grating sensors especially in biological sensing. Therefore, in this work, we have introduced a novel plus shaped cavity (PSC) in optical fiber model and used it for the detection of haemoglobin (Hb) refractive index (RI). The numerical analysis of designed model is done by the testing of single and double vertical slots cavity in optical fiber core structure. The testing of designed sensor model is done at the wavelength of 800 nm at which the RI of oxygenated and deoxygenated Hb is 1.392 and 1.389, respectively. The analysis of reported PSC sensor model is done in the wide range of Hb RI from 1.333 to 1.392. The tested range of RI corresponds to the Hb concentration from 0 to 140 gl-1. The obtained results states that for the tested range of RI, the autocorrelation coefficientt of R2 = 99.51 % is achieved. The analysis of projected work is done by using finite difference time domain (FDTD) method. The introduction of PSC can increase in sensitivity. In proposed PSC, the length and width of created slots are 1.8 μm and 1 μm, respectively, which is quite enough to observe the response of analytes RI. This can minimize the creation of multiple gratings required for observing the analyte response.