Search

Monitoring the dynamic humidity requires sensors with fast response and anti-electromagnetic interference, especially for human respiration. Here, an ultrafast fiber-optic breath sensor based on the humidity-sensitive characteristics of gelatin film is proposed and experimentally demonstrated. The sensor consists of a microknot resonator superimposed on a Mach-Zehnder (MZ) interferometer produced by a tapered single-mode fiber, which has an ultrafast response (84 ms) and recovery time (29 ms) and a large dynamic transmission range. The humidity in dynamic ambient causes changes in the refractive index of gelatin coating, which could trigger spectral intensity transients that can be explicitly distinguished between the two states. The sensing principle is analyzed using the traditional transfer-matrix analysis method. The influence of coating thickness on the sensor's trigger threshold is further investigated. Experiments on monitoring breath patterns indicate that the proposed breath sensor has high repeatability, reliability, and validity, which enable many other potential applications such as food processing, health monitoring, and other biomedical applications.

Hydrogels consisting of a three-dimensional hydrophilic network of biocompatible polymers have been widely used in tissue engineering. Owing to their tunable mechanical properties, hydrogels have been applied in both hard and soft tissues. However, most hydrogels lack self-adhesive properties that enable integration with surrounding tissues, which may result in suture or low repair efficacy. Self-adhesive hydrogels (SAHs), an emerging class of hydrogels based on a combination of three-dimensional hydrophilic networks and self-adhesive properties, continue to garner increased attention in recent years. SAHs exhibit reliable and suitable adherence to tissues, and easily integrate into tissues to promote repair efficiency. SAHs are designed either by mimicking the adhesion mechanism of natural organisms, such as mussels and sandcastle worms, or by using supramolecular strategies. This review summarizes the design and processing strategies of SAHs, clarifies underlying adhesive mechanisms, and discusses their applications in tissue engineering, as well as future challenges.

Light-sheet microscopy has emerged as the preferred means for high-throughput volumetric imaging of cleared tissues. However, there is a need for a user-friendly system that can address diverse imaging applications with varied requirements in terms of resolution (mesoscopic to sub-micron), sample geometry (size, shape, and number), and compatibility with tissue-clearing protocols of different refractive indices. We present a hybrid system that combines a novel non-orthogonal dual-objective and conventional open-top light-sheet architecture for highly versatile multi-scale volumetric imaging. One sentence summary Glaser et al. describe a hybrid open-top light-sheet microscope to image cleared tissues at mesoscopic to sub-micron resolution and depths of up to 1 cm.

This work reports a microsphere laser at ∼2.0 μm in a Tm3+-doped ZrF4-BaF2-YF3-AlF3 (ZBYA) fluoride glass. The ZBYA glass microsphere was fabricated by reflowing the tip of a 1.0 mol% Tm3+-doped ZBYA glass fiber with a CO2 laser. By using a fiber taper for input and output coupling in the Tm3+-doped ZBYA microsphere, single and multi-mode laser outputs at around 2.0 μm were observed under 808 nm laser excitation. The radiation lifetime and emission cross-section of Tm3+ ions in ZBYA glass were calculated to be 6.42 ms and 5.86 × 10−21 cm2, respectively. Our results indicate that the Tm3+-doped ZBYA fluoride glass has potential applications for 2.0 μm lasers.

We demonstrate a novel, to the best of our knowledge, refractive index (RI) sensor based on the Vernier effect in dual-microfiber coupler (MFC) structures. The sensor sensitivity was studied both theoretically and experimentally. The numerical results show that by tracing the wavelength shifts of the envelope formed by the Vernier effect, the sensitivity can be improved by several times compared to that obtained for normal coupler-based sensors. In this Letter, two MFCs with a width and free spectral range (FSR) of ∼ 3.5 µ m and 6 nm, respectively, were fabricated. Based on the sensitivity of 5820 nm/RIU for a single coupler, we experimentally achieved an ultra-high sensitivity of 126,540 nm/RIU using dual MFCs by the Vernier effect in the RI range of 1.3350 to 1.3455, which shows good agreement with numerical simulations. The proposed all-fiber RI sensor has the advantages of high sensitivity and low cost and can find applications in chemical and biological detection as well as electronic/magnetic field measurement.

We present cleared-tissue axially swept light-sheet microscopy (ctASLM), which enables isotropic, subcellular resolution imaging with high optical sectioning capability and a large field of view over a broad range of immersion media. ctASLM can image live, expanded, and both aqueous and non-aqueous chemically cleared tissue preparations. Depending on the optical configuration, ctASLM provides up to 260 nm of axial resolution, a three to tenfold improvement over confocal and other reported cleared-tissue light-sheet microscopes. We imaged millimeter-scale cleared tissues with subcellular three-dimensional resolution, which enabled automated detection of multicellular tissue architectures, individual cells, synaptic spines and rare cell–cell interactions. Cleared-tissue axially swept light-sheet microscopy (ctASLM) enables high-speed, refraction index-independent imaging of live, cleared and expanded samples with isotropic, submicron resolution.

A high-sensitivity ethanol gas sensor based on two microfiber couplers and the Vernier effect is examined in this Letter using the unique variation rate conversion point characteristics. The output spectrum of the two couplers connected in parallel are superimposed to form a symmetrical envelope curve, showing high responsivity to variations in the external environment. Ethanol sensitivity was achieved by coating the waist region of the coupler with a mixture of Nile red and polymethyl methacrylate. When the concentration of ethanol gas changes, the envelope spectrum shifts. Experimental results show that a high responsivity of 160 pm/ppm can be obtained by tracing the reference peaks in the envelope curve and that the response and recovery times are on the order of seconds.

In this Letter, we report lasing at 2.3 µm in Tm 3 + -single-doped and Tm 3 + / Ho 3 + -codoped fluorotellurite glass microsphere resonators. By employing a 793 nm diode laser as a pump and exploiting whispering gallery mode microresonators (WGMRs), dual-wavelength lasing at 1.9 and 2.3 µm and triple-wavelength lasing at 1.9, 2.07, and 2.3 µm are achieved in Tm 3 + -doped and Tm 3 + / Ho 3 + -codoped microspheres, respectively. The introduction of Ho 3 + ions significantly reduces the lasing threshold of Tm 3 + at 2.3 µm because of energy transfer.

Simultaneous 1.50 μm, 1.84 μm and 2.08 μm laser emission is observed in a Ho3+/Tm3+ co-doped ZrF4–BaF2–YF3–AlF3 (ZBYA) fluoride glass microsphere when pumped using a 793 nm laser diode. The ZBYA fluoride glass microsphere was prepared using a CO2 laser heating method and whispering-gallery modes (WGM) were excited when the pump light was coupled using a tapered fiber. The introduction of Ho3+ ions reduced the population of the long-lived Tm3+:3F4 level and removed the 3H4→ 3F4 self-termination effect, resulting in the population of the Ho3+:5I7 level through a resonant energy transfer process. As the 793 nm laser pump power grows, lasing occurs initially at 2.08 μm, followed by the cascade outputs at 1.50 μm and 1.84 μm.

peer-reviewed A novel multi-wavelength mode-locked Erbium-doped fiber laser with tungsten disulfide (WS2) combined with a microfiber knot is described. This hybrid fiber structure facilitates strong light matter interaction between the saturated absorption of the WS2 material and high optical non-linearity of the microfiber knot. It is demonstrated experimentally that the novel fiber laser works stably in the absence of an external comb filter, with the generation of stable multi-wavelength picosecond pulses. In the multi-wavelength lasing regime, up to 7-wavelength stable mode-locked pulses are obtained using a polarization controller with the pump power at ~250 mW. The pulse period and the pulse width are 188.7 ns and 16.3 ps respectively. In addition, the number of multi-wavelength lasing channels can be changed by simply adjusting the microfiber knot size. Experimental results show the laser to have a stable output over 12 hours recording period. The results of this investigation demonstrate that the optical microfiber knot with a WS2 overlay based fiber laser device can operate as a highly nonlinear optical component and a saturable absorber. The proposed multi-wavelength lasing device can therefore be widely used for non-linear and ultrafast photonics and has a number of advantages compared to similar devices using more conventional technologies, including low cost and good stability

Objectives Dental implants are major treatment options for restoring teeth loss. Biological processes at the implant‐tissue interface are critical for implant osseointegration. Superior mechanical properties of the implant constitute a major challenge for traditional histological techniques. It is imperative to develop new technique to investigate the implant‐tissue interface. Materials and methods Our laboratory developed the polyethylene glycol (PEG)‐associated solvent system (PEGASOS) tissue clearing method. By immersing samples into various chemical substances, bones and teeth could be turned to transparent with intact internal structures and endogenous fluorescence being preserved. We combined the PEGASOS tissue clearing method with transgenic mouse line and other labelling technique to investigate the angiogenesis and osteogenesis processes occurring at the implant‐bone interface. Results Clearing treatment turned tissue highly transparent and implant could be directly visualized without sectioning. Implant, soft/hard tissues and fluorescent labels were simultaneously imaged in decalcified or non‐decalcified mouse mandible samples without disturbing their interfaces. Multi‐channel 3‐dimensional image stacks at high resolution were acquired and quantified. The processes of angiogenesis and osteogenesis surrounding titanium or stainless steel implants were investigated. Conclusions Both titanium and stainless steel implants support angiogenesis at comparable levels. Successful osseointegration and calcium precipitation occurred only surrounding titanium, but not stainless steel implants. PEGASOS tissue clearing method provides a novel approach for investigating the interface between implants and hard tissue.