An AuNPs/Mesoporous NiO/Nickel Foam Nanocomposite as a Miniaturized Electrode for Heavy Metal Detection in Groundwater

Heavy metals,notably Pb2+and Cu^(2+),are some of the most persistent contaminants found in groundwater.Frequent monitoring of these metals,which relies on efficient,sensitive,cost-effective,and reliable methods,is a necessity.We present a nanocomposite-based miniaturized electrode for the concurrent measurement of Pb2+and Cu^(2+)by exploiting the electroanalytical technique of square wave voltammetry.We also propose a facile in situ hydrothermal calcination method to directly grow binder-free mesoporous Ni O on a three-dimensional nickel foam,which is then electrochemically seeded with gold nanoparticles(Au NPs).The meticulous design of a low-barrier Ohmic contact between mesoporous Ni O and Au NPs facilitates target-mediated nanochannel-confined electron transfer within mesoporous Ni O.As a result,the heavy metals Pb2+(0.020 mg.L^(-1)detection limit;2.0–16.0 mg.L^(-1)detection range)and Cu^(2+)(0.013 mg.L^(-1)detection limit;0.4–12.8 mg.L^(-1)detection range)can be detected simultaneously with high precision.Furthermore,other heavy metal ions and common interfering ions found in groundwater showed negligible impacts on the electrode’s performance,and the recovery rate of groundwater samples varied between 96.3%±2.1%and 109.4%±0.6%.The compactness,flexible shape,low power consumption,and ability to remotely operate our electrode pave the way for onsite detection of heavy metals in groundwater,thereby demonstrating the potential to revolutionize the field of environmental monitoring.

Design and realization of 3D printed fiber-tip microcantilever probes applied to hydrogen sensing

Cantilevers in microelectromechanical systems have the advantages of non-labeling,real-time detection,positioning,and specificity.Rectangular solid,rectangular hollow,and triangular microcantilevers were fabricated on an optical fiber tip via two-photon polymerization.The mechanical properties were characterized using finite element simulations.Coating the microcantilever with a palladium film enabled high sensitivity and rapid hydrogen detection.The shape of the cantilever determines the sensitivity,whereas the thickness of the palladium film determines the response time.Additional microelectromechanical systems can be realized via polymerization combined with optical fibers.

Fiber-tip polymer clamped-beam probe for high-sensitivity nanoforce measurements

Micromanipulation and biological,material science,and medical applications often require to control or measure the forces asserted on small objects.Here,we demonstrate for the first time the microprinting of a novel fiber-tip-polymer clamped-beam probe micro-force sensor for the examination of biological samples.The proposed sensor consists of two bases,a clamped beam,and a force-sensing probe,which were developed using a femtosecond-laser-induced two-photon polymerization(TPP)technique.Based on the finite element method(FEM),the static performance of the structure was simulated to provide the basis for the structural design.A miniature all-fiber micro-force sensor of this type exhibited an ultrahigh force sensitivity of 1.51 nmμN−1,a detection limit of 54.9 nN,and an unambiguous sensor measurement range of~2.9 mN.The Young’s modulus of polydimethylsiloxane,a butterfly feeler,and human hair were successfully measured with the proposed sensor.To the best of our knowledge,this fiber sensor has the smallest force-detection limit in direct contact mode reported to date,comparable to that of an atomic force microscope(AFM).This approach opens new avenues towards the realization of small-footprint AFMs that could be easily adapted for use in outside specialized laboratories.As such,we believe that this device will be beneficial for high-precision biomedical and material science examination,and the proposed fabrication method provides a new route for the next generation of research on complex fiber-integrated polymer devices.

Encrypted optical fiber tag based on encoded fiber Bragg grating array

Optical fibers are typically used in telecommunications services for data transmission,where the use of fiber tags is essential to distinguish between the different transmission fibers or channels and thus ensure the working functionality of the communication system.Traditional physical entity marking methods for fiber labeling are bulky,easily confused,and,most importantly,the label information can be accessed easily by all potential users.This work proposes an encrypted optical fiber tag based on an encoded fiber Bragg grating(FBG)array that is fabricated using a point-by-point femtosecond laser pulse chain inscription method.Gratings with different resonant wavelengths and reflectivities are realized by adjusting the grating period and the refractive index modulations.It is demonstrated that a binary data sequence carried by a fiber tag can be inscribed into the fiber core in the form of an FBG array,and the tag data can be encrypted through appropriate design of the spatial distributions of the FBGs with various reflection wavelengths and reflectivities.The proposed fiber tag technology can be used for applications in port identification,encrypted data storage,and transmission in fiber networks.

A Probe-Shaped Sensor With FBG and Fiber-Tip Bubble for Pressure and Temperature Sensing

A probe-shaped sensor for simultaneous temperature and pressure measurement was reported in this article.The effective length of the sensor was〜2 mm,consisting of a fiber Bragg grating(FBG)and a Fabry-Perot interferometer(FPI)with a nano silica diaphragm.The response sensitivities of the sensor for pressure and temperature were measured as-0.98 nm/MPa and 11.10pm/℃,respectively.This sensor had an extremely low cross-sensitivity between pressure and temperature,which provided a significant potential in dual-parameter sensing.

Femtosecond laser 3D printed micro objective lens for ultrathin fiber endoscope

The most important optical component in an optical fiber endoscope is its objective lens.To achieve a high imaging performance level,the development of an ultra-compact objective lens is thus the key to an ultra-thin optical fiber endoscope.In this work,we use femtosecond laser 3D printing to develop a series of micro objective lenses with different optical designs.The imaging resolution and field-of-view performances of these printed micro objective lenses are investigated via both simulations and experiments.For the first time,multiple micro objective lenses with different fields of view are printed on the end face of a single imaging optical fiber,thus realizing the perfect integration of an optical fiber and objective lenses.This work demonstrates the considerable potential of femtosecond laser 3D printing in the fabrication of micro-optical systems and provides a reliable solution for the development of an ultrathin fiber endoscope.

Study of Temporal Thermal Response of Microfiber Bragg Grating

Fiber Bragg grating has been successfully fabricated in the silica microfiber by the use of femtosecond laser point-by-point inscription.Temporal thermal response of the fabricated silica microfiber Bragg grating has been measured by the use of the CO_(2) laser thermal excitation method,and the result shows that the time constant of the microfiber Bragg grating is reduced by an order of magnitude compared with the traditional single-mode fiber Bragg grating and the measured time constant is〜21 ms.

Microstructured Cantilever Probe on Optical Fiber Tip for Microforce Sensor

Benefiting from the great advances of the femtosecond laser two-photon polymerization(TPP)technology,customized microcantilever probes can be accurately 3-dimensional(3D)manufactured at the nanoscale size and thus have exhibited considerable potentials in the fields of microforce,micro-vibration,and microforce sensors.In this work,a controllable microstructured cantilever probe on an optical fiber tip for microforce detection is demonstrated both theoretically and experimentally.The static performances of the probe are firstly investigated based on the finite element method(FEM),which provides the basis for the structural design.The proposed cantilever probe is then 3D printed by means of the TPP technology.The experimental results show that the elastic constant k of the proposed cantilever probe can be actively tuned from 2.46N/m to 62.35N/m.The force sensitivity is 2.5nm/μN,the Q-factor is 368.93,and the detection limit is 57.43nN.Moreover,the mechanical properties of the cantilever probe can be flexibly adjusted by the geometric configuration of the cantilever.Thus,it has an enormous potential for matching the mechanical properties of biological samples in the direct contact mode.

Single-mode helical Bragg grating waveguide created in a multimode coreless fiber by femtosecond laser direct writing

We demonstrate the fabrication of single-mode helical Bragg grating waveguides(HBGWs)in a multimode core-less fiber by using a femtosecond laser direct writing technique.This approach provides a single-step method for creating Bragg grating waveguides.Specifically,the unique helical structure in such an HBGW serves as a depressed cladding waveguide and also generates strong Bragg resonance due to its periodicity.Effects of pulse energy,helical diameter,and helical pitch used for fabricating HBGWs were studied,and a single-mode HBGW with a narrow bandwidth of 0.43 nm and a Bragg wavelength of 1546.50 nm was achieved by using appropriate parameters,including a diameter of 10μm and a helical pitch of 1.07μm.The measured cross-sectional refractive index profile indicates that a depressed cladding waveguide has been created in this single-mode HBGW.Moreover,five single-mode HBGWs with various Bragg wavelengths were successfully fabricated by controlling the helical pitch,and this technique could be used for achieving a wavelength-division-multiplexed HBGW array.Then,the temperature and strain responses of the fabricated single-mode HBGW were tested,exhibiting a temperature sensitivity of 11.65 pm/℃ and a strain sensitivity of 1.29 pm/με,respectively.In addition,the thermal stability of the single-mode HBGW was also studied by annealing at a high temperature of 700℃ for 15 h.The degeneration of the single-mode waveguide into a multimode waveguide was observed during the isothermal annealing process,and the peak reflection and the Bragg wavelength of the fundamental mode exhibited a decrease of∼7 dB and a“blue”shift of 0.36 nm.Hence,such a femtosecond laser directly written single-mode HBGW could be used in many applications,such as sapphire fiber sensors,photonic integrated circuits,and monolithic waveguide lasers.