Hydrogen is widely used in industrial production, clinical medicine, and as fuel. Hydrogen becomes explosive when the hydrogen-air mixture ranges from 4 to 76 vol%; thus, a rapid hydrogen concentration...
Ultrasensitive nanomechanical instruments, e.g., atomic force microscopy (AFM), can be used to perform delicate biomechanical measurements and reveal the complex mechanical environment of biological processes. However, these instruments are limited because of their size and complex feedback system. In this study, we demonstrate a miniature fiber optical nanomechanical probe (FONP) that can be used to detect the mechanical properties of single cells and in vivo tissue measurements. A FONP that can operate in air and in liquids was developed by programming a microcantilever probe on the end face of a single-mode fiber using femtosecond laser two-photon polymerization (TPP) nanolithography. To realize stiffness matching of the FONP and sample, a strategy of customizing the microcantilever’s spring constant according to the sample was proposed based on structure-correlated mechanics. As a proof-of concept, three FONPs with spring constants varying from 0.421 N/m to 52.6 N/m by more than two orders of magnitude were prepared. The highest microforce sensitivity was 54.5 nm/μN and the detection limit was 2.1 nN. The Young's modulus of heterogeneous soft materials, such as polydimethylsiloxane, muscle tissue of living mice, onion cells, and MCF-7 cells, were successfully measured, which validating the broad applicability of this method. Our strategy provides a universal protocol for directly programming fiber-optic AFMs. Moreover, this method has no special requirements for the size and shape of living biological samples, which is infeasible when using commercial AFMs. FONP has made substantial progress in realizing basic biological discoveries, which may create new biomedical applications that cannot be realized by current AFMs.
Nanomechanical sensors made from suspended graphene are sensitive to pressure changes. However, these devices typically function by obtaining an electrical signal based on the static displacement of a suspended graphene membrane and so, in practice, have limited sensitivity and operational range. The present work demonstrates an optomechanical Au/graphene membrane-based gas pressure sensor with ultrahigh sensitivity. This sensor comprises a suspended Au/graphene membrane appended to a section of hollow-core fiber to form a sealed Fabry–Pérot cavity. In contrast to conventional nanomechanical pressure sensors, pressure changes are monitored via resonant sensing with an optical readout. A miniature pressure sensor based on this principle was able to detect an ultrasmall pressure difference of 1 × 10–7 mbar in the ultrahigh-vacuum region with a pressure range of 4.1 × 10–5 to 8.3 × 10–6 mbar. Furthermore, this pressure sensor can work over an extended pressure range of 7 × 10–6 mbar to 1000 mbar at room temperature, outperforming commercial pressure sensors. Similar results were obtained using both the fundamental and higher-order resonant frequencies but with the latter providing improved sensitivity. This sensor has a wide range of potential applications, including indoor navigation, altitude monitoring, and motion detection.
Nanomechanical bolometers have proven to be well suited to the analysis of light. However, conventional wafer-based devices have limited practical applications because they require special vacuum chambers, cryogenic temperatures, bulky space optical components, and/or complex circuitry. The present work developed a nanoscale optomechanical bolometer intended for photothermal sensing using an all-optical actuation and measurement approach. The proposed bolometer is compact and has an integrated all-optical-fiber structure based on fabricating a Fabry− Perot interferometer incorporating multilayer graphene at the fiber tip and packaged in a small vacuum-sealed tube. This microscale vacuum packaging doubled the signal-to-noise ratio compared with that in air. This miniature all-fiber nanoscale optomechanical bolometer also exhibited a high resolution with photothermal sensitivities of approximately 6.23 and 6.44 kHz/μW when using the second-order mode at room temperature and 0 °C, respectively. This design could be beneficial for applications outside specialized laboratories with uses in the fields of medicine, industrial manufacturing, nanoscience, and astronomy.
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