Robust and low-cost interrogation technique for integrated photonic biochemical sensors based on Mach–Zehnder interferometers

We describe and experimentally demonstrate a measuring technique for Mach–Zehnder interferometer(MZI)based integrated photonic biochemical sensors. Our technique is based on the direct measurement of phase changes between the arms of the MZI, achieved by signal modulation on one of the arms of the interferometer together with pseudoheterodyne detection, and it allows us to avoid the use of costly equipment such as tunable light sources or spectrum analyzers. The obtained output signal is intrinsically independent of wavelength, power variations, and global thermal variations, making it extremely robust and adequate for use in real conditions. Using a silicon-on-insulator MZI, we demonstrate the real-time monitoring of refractive index variations and achieve a detection limit of 4.1 × 10^(-6)refractive index units(RIU).

Design of Mach-Zehnder Interferometer and Ring Resonator for Biochemical Sensing

We proposed a compact design of an optical biochemical sensor based on the Mach-Zehnder interferometer （MZI）, which was coupled by a ring resonator （RR） as a sensing tool. The sensor sensitivity has been determined by power difference at the output ports. The sensor enhancement has been optimized by numerically evaluating the geometrical parameters of the MZ! and RR. A great sensor sensitivity depicted by Fano resonance characteristic has been demonstrated as a function of the round trip phase in the range of 4×10^-4 - 4×10^-4, which was changed by the presence of the sample solution in the sensing area. This optimum sensitivity has been obtained for the values of two coupling coefficients of the MZI k1 =k2 =0.5/mm and the coupling coefficient between the MZI arm and RR KR = 0.5/ram. Furthermore, a good profile of sensitivity exchange has been exhibited by inducing the direct current voltage to the coupling region of k R. Finally, the output power transmission of the ring-coupled arm was depicted as a function of tunable k R.

Synthesis of fluorescent bisboronic acid sensors and their recognition of mono-/oligo-saccharides

Sensors capable of recognizing cell surface carbohydrates,such as sialyl Lewis X（sLe-x）,are invaluable research tools and for the diagnosis and early detection of many forms of cancer.In this paper,we report the design and synthesis of a series of bisboronic acids 6（a-f） as fluorescent sensors towards mono-/oligosaccharides.Among them,compounds 6d and 6e showed strong binding affinities with glucose and fructose,while compound 6c,in which two anthracene-based boronic acid units were linked by a hexamethylene spacer,was able to recognize sLe-x selectivity and stained HEPG2 cells at 1 μmoI/L.

Laser-induced graphene for bioelectronics and soft actuators

Laser-assisted process can enable facile,mask-free,large-area,inexpensive,customizable,and miniaturized patterning of laser-induced porous graphene(LIG)on versatile carbonaceous substrates(e.g.,polymers,wood,food,textiles)in a programmed manner at ambient conditions.Together with high tailorability of its porosity,morphology,composition,and electrical conductivity,LIG can find wide applications in emerging bioelectronics(e.g.,biophysical and biochemical sensing)and soft robots(e.g.,soft actuators).In this review paper,we first introduce the methods to make LIG on various carbonaceous substrates and then discuss its electrical,mechanical,and antibacterial properties and biocompatibility that are critical for applications in bioelectronics and soft robots.Next,we overview the recent studies of LIG-based biophysical(e.g.,strain,pressure,temperature,hydration,humidity,electrophysiological)sensors and biochemical(e.g.,gases,electrolytes,metabolites,pathogens,nucleic acids,immunology)sensors.The applications of LIG in flexible energy generators and photodetectors are also introduced.In addition,LIG-enabled soft actuators that can respond to chemicals,electricity,and light stimulus are overviewed.Finally,we briefly discuss the future challenges and opportunities of LIG fabrications and applications.

Recent Progress in Fiber Optofluidic Lasing and Sensing

Fiber optofluidic laser(FOFL)integrates optical fiber microcavity and microfluidic channel and provides many unique advantages for sensing applications.FOFLs not only inherit the advantages of lasers such as high sensitivity,high signal-to-noise ratio,and narrow linewidth,but also hold the unique features of optical fiber,including ease of integration,high repeatability,and low cost.With the development of new fiber structures and fabrication technologies,FOFLs become an important branch of optical fiber sensors,especially for application in biochemical detection.In this paper,the recent progress on FOFL is reviewed.We focuse mainly on the optical fiber resonators,gain medium,and the emerging sen sing applicatio ns.The prospects for FOFL are also discussed.We believe that the FOFL sensor provides a promising technology for biomedical analysis and environmental monitoring.