Near-infrared microfiber Bragg grating for sensitive measurement of tension and bending.

Fiber-optic devices working in the visible and near-infrared windows are attracting attention due to the rapid development of biomedicine that involves optics. In this work, we have successfully realized the fabrication of near-infrared microfiber Bragg grating (NIR-µFBG), which was operated at the wavelength of 785 nm, by harnessing the fourth harmonic order of Bragg resonance. The NIR-µFBG provided the maximum sensitivity of axial tension and bending to 211 nm/N and 0.18 nm/deg, respectively. By conferring the considerably lower cross-sensitivity, such as response to temperature or ambient refractive index, the NIR-µFBG can be potentially implemented as the highly sensitive tensile force and curve sensor.

Surface-wettable nonenzymatic fiber-optic sensor for selective detection of hydrogen peroxide.

A micro-nanostructure-based surface-modified fiber-optic sensor has been developed herein to selectively detect hydrogen peroxide (H2O2). In our design, phenylboronic ester-modified polymers were used as a modified cladding medium that allows chemo-optic transduction. Sensing is mechanistically based on oxidation and subsequent hydrolysis of the phenylboronic ester-modified polymer, which modulates hydrophobic properties of fiber-optic devices, which was confirmed during characterization of the chemical functional group and hydrophobicity of the active sensing material. This work illustrates a useful strategy of exploiting principles of chemical modifications to design surface-wettable fiber-optic sensing devices for detecting reactive species of broad relevance to biological and environmental analyses.

A capillary-aided microfiber Bragg grating pH sensor for hydrovoltaic technology.

Hydrovoltaic is an emerging technology that aims to harvest energy from water flow and evaporation, in which the plasmonic hydrogen ions are generated by the interaction between water and hydrovoltaic device. However, the volume of the water sample for the interaction is usually ultra-small due to the compact size of hydrovoltaic device, making the quantification and characterization of the hydrogen ions in such water sample an elusive goal. To address this issue, a miniature fiber-optic pH probe is proposed using a unilaterally tapered-microfiber Bragg grating. The microfiber Bragg grating has an intrinsic Bragg reflection signal with a narrow linewidth. The fiber probe is functionalized by coating the sodium alginate, which can respond to the variation of pH mediated by the alteration of the hydrophilicity. The rigidity and robustness of microfiber Bragg grating facilitates the encapsulation of the sensor into a sampling capillary, allowing for the detection of trace aqueous sample less than 2 µL. The pH sensitivity of the tapered-µFBG-based sensor is 62.8 p.m./pH (R2 = 0.995) with a limit resolution of 0.096 pH. The sensor performed a practical application in the monitoring and characterization of the hydrovoltaic microdevice, which can generate microcurrent as soaked in the water. This work demonstrates a promising technology in the fields of materials, energy, biology and medicine, in which the detection of the microsamples is inevitable.

Fiber-optic drug delivery strategy for synergistic cancer photothermal-chemotherapy.

Chemotherapy is one of the conventional treatments for cancer in clinical practice. However, poor delivery efficiency, systemic toxicity, and the lack of pharmacokinetic monitoring during treatment are the critical limitations of current chemotherapy. Herein, we reported a brand-new antitumor drug delivery strategy that harnesses an optical fiber endoscopically therapeutic probe. The fiber probe carries photosensitizers in the fiber core and antitumor agents on the fiber surface mediated by a temperature-responsive hydrogel film, giving rise to an activable photothermal-chemotherapy that orchestrates the localized hyperthermia and thermal-stimuli drug release to the tumor lesion. Furthermore, the dynamical drug release and in-situ temperature can be real-time supervised through the built-in fiber sensors, including the reflective Mach-Zehnder interferometer and fiber Bragg grating, to visualize the therapy process and thus improve the safety of treatment. Compared with conventional methods, the fiber-optic drug delivery can adequately take advantage of the chemotherapeutics through collaboratively recruiting the photoheating-mediated enhanced permeability and the hydrogel particle-assisted high drug retention, shedding new light on a "central-to-peripheral" drug pervasion and retention mechanism to destroy tumors completely. The fiber-optic chemotherapy strategy incorporates precise drug delivery, accurate controllability of drug release, high drug permeability and retention in tumor, low off-target rate, and real-time drug release and temperature feedback, performing a straightforward and precise photothermal-chemotherapy pathway. More than that, the proposed strategy holds tremendous promise to provide a revolutionized on-demand drug delivery platform for the highly efficient evaluation and screening of antitumor pharmaceuticals.