Relay-type sensing mode:A strategy to push the limit on nanomechanical sensor sensitivity based on the magneto lever

Ultrasensitive molecular detection and quantization are crucial for many applications including clinical diagnostics,functional proteomics,and drug discovery;however,conventional biochemical sensors cannot satisfy the stringent requirements,and this has resulted in a long-standing dilemma regarding sensitivity improvement.To this end,we have developed an ultrasensitive relay-type nanomechanical sensor based on a magneto lever.By establishing the link between very weak molecular interaction and five orders of magnitude larger magnetic force,analytes at ultratrace level can produce a clearly observable mechanical response.Initially,proof-of-concept studies showed an improved detection limit up to five orders of magnitude when employing the magneto lever,as compared with direct detection using probe alone.In this study,we subsequently demonstrated that the relay-type sensing mode was universal in application ranging from micromolecule to macromolecule detection,which can be easily extended to detect enzymes,DNA,proteins,cells,viruses,bacteria,chemicals,etc.Importantly,we found that,sensitivity was no longer subject to probe affinity when the magneto lever was sufficiently high,theoretically,even reaching single-molecule resolution.

Whispering-gallery mode lasing from polymer microsphere for humidity sensing

Microlasers based on high quality （Q） whispering-gallery mode （WGM） resonance are pronfising low threshold laser sources for bio-sensing and imaging applications. In this Letter, dye-doped polymer microspheres were fabricated by a controlling emulsion solvent evaporation method. WGM lasing with low threshold and high Q factors was realized in an individual microsphere under femtosecond laser pumping. The slight change of environmental relative humidity （RH） can be monitored by measuring the shift of the lasing modes at tile ex- posure of water molecules, which dcmonstrates the sensitivity is as high as 6 pm/RH%. The results would offer an insight into employing microlasers as sensors.

Applied whispering gallery modes on ZnO nanorods coated glass for humidity sensing application

In this letter,a humidity sensor is demonstrated by applying a whispering gallery mode(WGM)from a microsphere resonator onto the ZnO nanorods coated glass surface.The diameter of the microsphere was 234μm and the glass surface was coated with ZnO nanorods using the hydrothermal method at growth duration of 12 h.A significant response to humidity level ranging from 35%RH to 85%RH has been observed with the sensitivity of 0.0142 nm/%RH.The proposed humidity sensor has successfully employed to enhance interaction between the whispering gallery mode evanescent and surrounds analyte with the assistance of ZnO nanorods coated glass.

Nonlinear Performance of MEMS Vibratory Ring Gyroscope

Micro-electro-mechanical system(MEMS)gyroscopes are an important sort of inertial sensor for identifying parameters of spinning structures,such as the spinning speed and angular deviation,based on the Coriolis effect.In this paper,the nonlinear mechanism of MEMS vibratory ring gyroscopes is analyzed by applying a fully coupled nonlinear model,in which the gyroscopic coupling and geometrically and structurally nonlinear couplings are all taken into account.The coupled differential equations governing the drive and sense motions are established via the Lagrangian equations.Numerical simulation is conducted,and the key nonlinear components and energy transfer behaviors between the drive and sense modes are elucidated.It is revealed that the cubic rigidity nonlinearity is another significant factor leading to the coupling between the drive and sense modes other than the gyroscopic coupling.Perturbation analysis is also carried out by using the method of multiple scales.The nonlinear frequency-amplitude responses of the drive and sense vibrations are obtained,and comprehensive parametric studies are performed.The significant effects of system damping,excitation amplitude,drive amplitude and spinning speed on the responses are discussed,which will facilitate to improve the nonlinear performance and sensitivity of the gyroscope.