Nanoscale electric field sensing using a levitated nano-resonator with net charge

The nanomechanical resonator based on a levitated particle exhibits unique advantages in the development of ultrasensitive electric field detectors. We demonstrate a three-dimensional, high-sensitivity electric field measurement technology using the optically levitated nanoparticle with known net charge. By scanning the relative position between nanoparticle and parallel electrodes, the three-dimensional electric field distribution with microscale resolution is obtained. The measured noise equivalent electric intensity with charges of 100e reaches the order of 1 μV·cm^(-1)·Hz^(-1/2)at 1.4 × 10^(-7) mbar. Linearity analysis near resonance frequency shows a measured linear range over 91 d B limited only by the maximum output voltage of the driving equipment. This work may provide an avenue for developing a high-sensitivity electric field sensor based on an optically levitated nano-resonator.

Actual Sensing Sensitivity and SNR Measurement of Optical Tweezers Based on Coulomb Force Input

Sensing sensitivity is the key performance of optical tweezers.By adjusting the frequency and magnitude of an applied Coulomb force as an input of optical tweezers,we directly measured the sensitivity and signal-to-noise ratio(SNR)of a system and indirectly calculated the actual noise magnitude.Combined with an output filter,the relationship between the SNR and bandwidths was studied.We established the simulation model of a system using Simulink and simulated the relationship between the SNR and magnitude of the input forces and filter bandwidths.In addition,we built an experimental system to determine the relationship between the SNR and the magnitude of the input forces and filter bandwidths.The actual minimum detectable force was measured as 1.8275×10^(-17)N at a 1Hz bandwidth.The experimental results were correlated with the simulation and theoretical results,confirming the effectiveness of the proposed method and demonstrating the high sensitivity of vacuum optical tweezers as mechanical sensors.We proposed a novel method of calibration and measurement of system sensing parameters by applying an actual force that was more direct and precise than the theoretical calculation method that requires accurate fitting parameters,such as the particle radius and density.This method can be employed to analyze the system noise and phase characteristics to confirm and improve the real performance of the system.

Displacement Calibration of Optical Tweezers With Gravitational Acceleration

In recent years,levitated particles of optical traps in vacuum have shown the enormous potential for precision sensor development and new physics exploration.However,the accuracy of the sensor is still hampered by the uncertainty of the calibration factor relating the detected signal to the absolute displacement of the trapped particle.In this paper,we suggest and experimentally demonstrate a novel calibration method for optical tweezers based on free-falling particles in vacuum,where the gravitational acceleration is introduced as an absolute reference.Our work provides a calibration protocol with a great certainty and traceability,which is significant in improving the accuracy of precision sensing based on levitated optomechanical systems.

Existence of periodic solutions for second-order Hamiltonian systems with asymptotically linear conditions

We consider a class of asymptotically linear nonautonomous second- order Hamiltonian systems.Using the Saddle Point Theorem,we obtain the existence result,which extends some previously known results.

Clinical application of autologous chyle fat transplantation in the correction of sunken upper eyelid

Aim:We investigated the clinical application of autologous chyle fat in the correction of sunken upper eyelid.Methods:From November 2020 to October 2021,89 cases of correction with autologous chyle fat to sunken upper eyelid were performed(with or without other cosmetic procedures related to the eyes).An appropriate amount of fat was extracted from the superficial layer of the patient’s thigh and processed to chyle fat.About 0.5-2.8 mL of fat was injected under the orbicularis oculi muscle(roof-retro orbicularis oculi fat)or in the area where the orbital septal fat exists from the outer orbital margin of the upper eyelid.Results:In total,59 patients were followed up for 1-11 months after surgery.No infection,necrosis,vascular embolism,upper eyelid lumpiness,fat calcification,or liquefaction occurred in all patients,while seven cases showed inadequate correction.The depression basically disappeared,the shape was relatively full,the youthfulness was greatly improved,and the satisfaction of patients was high during the follow-up period.Conclusion:The correction with autologous chyle fat to sunken upper eyelid showed little trauma,short recovery periods,and satisfactory results,and it is worthy of being popularized and applied more widely.