High-sensitivity fiber-tip acoustic sensor with ultrathin gold diaphragm.

Miniature acoustic sensors with high sensitivity are highly desired for applications in medical photoacoustic imaging, acoustic communications and industrial nondestructive testing. However, conventional acoustic sensors based on piezoelectric, piezoresistive and capacitive detectors usually require a large element size on a millimeter to centimeter scale to achieve a high sensitivity, greatly limiting their spatial resolution and the application in space-confined sensing scenarios. Herein, by using single-crystal two-dimensional gold flakes (2DGFs) as the sensing diaphragm of an extrinsic Fabry-Perot interferometer on a fiber tip, we demonstrate a miniature optical acoustic sensor with high sensitivity. Benefiting from the ultrathin thickness (∼8 nm) and high reflectivity of the 2DGF, the fiber-tip acoustic sensor gives an acoustic pressure sensitivity of ∼300 mV/Pa in the frequency range from 100 Hz to 20 kHz. The noise-equivalent pressure of the fiber-tip acoustic sensor at the frequency of 13 kHz is as low as 62.8 µPa/Hz1/2, which is one or two orders of magnitude lower than that of reported optical acoustic sensors with the same size.

Strategies and mechanisms targeting Enterococcus faecalis biofilms associated with endodontic infections: a comprehensive review.

Enterococcus faecalis is one of the main microorganisms that infects root canals, ranking among the most prevalent microorganisms associated with endodontic treatment failure. Given its pervasive presence in persistent endodontic infections, the successful elimination of Enterococcus faecalis is crucial for effective endodontic treatment and retreatment. Furthermore, Enterococcus faecalis can form biofilms - defense structures that microbes use to fight environmental threats. These biofilms confer resistance against host immune system attacks and antibiotic interventions. Consequently, the presence of biofilms poses a significant challenge in the complete eradication of Enterococcus faecalis and its associated disease. In response, numerous scholars have discovered promising outcomes in addressing Enterococcus faecalis biofilms within root canals and undertaken endeavors to explore more efficacious approaches in combating these biofilms. This study provides a comprehensive review of strategies and mechanisms for the removal of Enterococcus faecalis biofilms.

Atomically Smooth Gold Microflake-Enabled Fiber-Tip Fabry-Perot Interferometer for Temperature and Pressure Sensing.

Fiber-tip sensors based on the Fabry-Perot interferometer (FPI) are one of the most widely used devices for temperature and pressure measurements in space-confined scenarios. However, the deposited metal films with a polycrystalline structure tend to form microcracks under strain, which can undermine the optical quality factor and thus sensing performance of these fiber-tip sensors. Here, we demonstrate an atomically smooth gold microflake (GMF)-enabled fiber-tip FPI sensor with a Q factor as high as 628. Benefiting from the high reflectivity and flexibility of GMFs and the elasticity of the PDMS spacer, the fiber-tip FPI can maintain stable sensing performance under large deformation. For temperature sensing, the fiber-tip sensor exhibits a linear response to the temperature in the range 28-40 °C with a sensitivity as high as 1.74 nm °C-1. To realize linear and sensitive pressure sensing, we design and fabricate a PDMS clamped-beam structure on the fiber tip using a soft lithography technique, achieving a sensitivity of 11.48 nm kPa-1. Moreover, simultaneous measurement of the temperature and pressure is also demonstrated using the wavelength demodulation method. The simple and cost-effective fabrication of the clamped beam and the transferable GMFs allow for the facile integration of high-quality FP cavities on fiber tips, opening new opportunities for developing optical sensors with miniaturized sizes.