Research On Micro-nano Resonant Mass Sensors Based On Feedback Control

Micro and nano resonant mass sensors are powerful tools for micro mass analysis and kinetic analysis of chemical reactions in chemistry and biophysics.The mechanics-based micro-nano-resonant mass sensor reveals the reaction steps and the reaction mechanism by testing the mass changes in the process,and has the advantages of simple structure,high interference immunity,easy integration and wide application.At present,the mass detection of micro-nano electromechanical system has not reached the accuracy of single molecule,which limits its application in biological and chemical reactions.This paper proposes a closed-loop feedback control system for micro-nano resonant mass sensors,which greatly improves the sensitivity of the sensors through feedback control techniques and achieves real-time detection of single-atom mass accuracy under ambient temperature conditions.Feedback-controlled micro-cantilever beam sensors are designed to reduce the equivalent mass of the cantilever beam by feedback control,thereby increasing its sensitivity.Using the bending vibration theory of continuous medium cantilever beams,the resonance characteristics of feedback controlled cantilever beams are studied,and the effects of the size,feedback gain and adsorption mass of the cantilever beam on the resonant frequency are obtained.Using the equivalent circuit simulation of dynamic models,the theoretical calculation results of the resonance characteristics are verified.The feedback control test of the fabricated sensor is carried out.The results show that both sensor sensitivity and measurement accuracy are improved with the increase of feedback gain.Atomic mass level resolution is achieved at room temperature and low vacuum using a feedback control system,and the effects of feedback gain on resonance frequency,feedback voltage,frequency fluctuation and quality factors are analyzed.The use of closed-loop feedback detection circuits can detect the mass of metal atoms and the mass of oxygen molecules in a low vacuum environment.The relative error of the detection is less than 5%.The kinetic model of hemoglobin oxygenation reaction is established,a method for determining the kinetic constants of hemoglobin oxygenation reaction based on the oxygenation reaction time of a single oxygen molecule is proposed,and the kinetic constants are determined.The detection sensitivity in atmospheric environment reaches the level of single ethanol molecule,avoiding complex and expensive ultra-low temperature vacuum system.Based on the theory of nonlocal continuum and Eulabernoulli beam,the multi-field coupled transverse free vibration differential equation of nanorobeam is established.The resonance characteristics of the feedback control nanorobeam are studied and the effect of non-local parameters,size parameters,feedback gain and the position and mass of adsorbed particles on the resonant frequency is obtained.The numerical results of resonant frequency are verified by molecular dynamics simulation.The results show that non-local parameters,size parameters,feedback gain and the position and mass of adsorbed particles have great influence on the vibration characteristics of the nano-beam.The zinc oxide nano-beam resonator is fabricated by top-down processing method,which reduces the damage of the nano-beam and improved the quality factor of the resonator.A closed-loop detection system based on phase-locked loop and frequency modulation technology is used to detect the electromagnetically excited zinc oxide nanobeam resonator.Experimental results show that the sensor has low phase noise and good closed-loop stability.The frequency modulation of the resonator is studied by using feedback technology.The sensitivity of the resonator can be greatly improved by feedback control,and the real-time detection of ethanol gas molecules is realized in room temperature and low vacuum environment.