FIG. 7.18 (a) Micromachined interferometric accelerometer showing the two optical beams, one from the diffraction grating and second from the mirror, which will interfere at the photodetector. (b) SiN nanobeam pair acting as “zipper” photonic crystal optomechanical cavity for accelerometry ( Krause et al., 2012 ). (c) Microdisk coupled to cantilever acting as a force sensor ( Doolin et al., 2014 ). The cantilever can deflect in both out-of-plane and in-plane mechanical modes. This results in the modulation of the disk's optical resonance frequency and is read out optically using a coupled fiber. (d) Split beam nano-cavity torque sensor ( Wu et al., 2014 ) showing the three degrees of freedom. One is out-of-plane rotation of the suspended mirror about the torsion beam, the second is in-plane bending about the torsion beam, and the third is out-of-plane bending of the cantilever mirror. More about this image found in (a) Micromachined interferometric accelerometer showing the two optical bea...

FIG. 8.3 (a) SEM image of a typical microfabricated Si-based cantilever sensor array without any surface modification. Reprinted with permission from Baller et al., Ultramicroscopy 82 (1–4), 1–9 (2000). Copyright 2000 Elsevier. (b) Schematic of H₂ sensing MC with an integrated Si photonics-based interferometric optical readout. An underlying waveguide allowed portions of the light passing through it to diffract and reflect from the bottom side of the sensing MC back into the waveguide. This resulted in optical interference, which was dependent on the separation distance between the waveguide and the MC. (c) SEM image of the fabricated H₂ sensing MC. The inset shows the A–A′ surface profile of the MC as measured by optical profilometry across the length. The location of the Si photonic waveguide is marked by dashed lines. It was hidden under a SiO_x planarization layer. Reprinted with permission from Gurusamy et al., Sens. Actuators B Chem. 281 , 335–342 (2019). Copyright 2019 Elsevier. (d) SEM image of the Ni-MOF-74 deposited resonant MC sensor used for CO detection where the material was coated onto the free-end of the MC. (e) Responses of the sensor to various concentrations of CO gas with a dynamic range from 10 ppb to 2.6 ppm. The inset depicts the magnified view of the sensor response to the lowest concentration of 10 ppb. Reprinted with permission from Lv et al., Sens. Actuators B Chem. 262 , 562–569 (2018). Copyright 2018 Elsevier. (f) SEM image of the carboxyl group functionalized mesoporous silica nanoparticles (C-MSNs) loaded resonant MC sensor used for NH₃ sensing. (g) Micro-gravimetric sensing curve of the C-MSNs decorated MC sensor to NH₃ vapor at various concentrations in the range of 5–300 ppb. The inset shows the relationship between NH₃ concentration and sensing response, which follows a Langmuir adsorption isotherm behavior; (h) repeatability test of the sensor to NH₃ for three cycles at 120 ppb concentration; (i) selectivity test of the sensor to eight kinds of interfering gases. Reprinted with permission from Liu et al., Sens. Actuators B Chem. 257 , 488–495 (2018b). Copyright 2018 Elsevier. (j) SEM image of the polymer nanocomposite MCs used for explosive vapor sensing. Reprinted with permission from Patil et al., Sens. Actuators B Chem. 192 , 444–451 (2014). Copyright 2014 Elsevier. More about this image found in (a) SEM image of a typical microfabricated Si-based cantilever sensor array...