Real-Time Detection and Control of Microchannel Resonance Frequency in Acoustic Trapping Systems by Monitoring Amplifier Supply Currents

Abstract

The utilization of bulk acoustic waves from a piezoelectric transducer for selective particle trapping under flow in a microchannel is limited by the high sensitivity of the resonance frequency to tolerances in device geometry, drift during trapping, and variations in the local flow or sample conditions in each channel. This is addressed by detecting the resonance condition based on the impedance minimum obtained by monitoring the amplitude of the stimulation voltage across the piezo transducer and utilizing real-time feedback to control the stimulation frequency. However, this requires an overlap in the frequency bandwidth of the detection and the stimulation system and is also limited by the decline in the acoustic trapping power when the stimulation and resonance frequency measurement are conducted simultaneously. Instead, we present a novel circuit implementation for on-chip real-time resonance frequency measurement and feedback control based on monitoring the current drawn from the amplifier used to stimulate the piezo transducer, since the need for high measurement sensitivity in this mode does not lower the power available for stimulation of the transducer. The enhanced level of control of acoustic trapping utilizing this current mode is validated for various localized channel perturbations, including drift, wash steps, and buffer swaps, as well as for selective sperm cell trapping from a heterogeneous sample that includes lysed epithelial cells.

Building and Realizing the Obstetrics and Gynecology Nursing Management Platform by Computer Information Technology under the Concept of Mindfulness Intervention

“…The physical and psychological conditions of pregnant women will inevitably affect the healthy development of the fetus. Ultrasound is used to monitor the frequency of emitted and received sound waves [ 31 ]. The difference between the frequencies of the emitted and received sound waves is represented by the Doppler frequency shift f D , and the calculation is shown as follows: …”

Optical feedback control loop for the precise and robust acoustic focusing of cells, micro- and nanoparticles

“…Goddard et al 27 Impedance 2006 Suthanthiraraj et al 28 Impedance 2012 Kalb et al 29 Impedance 2018 Farmehini et al 30 Electric current 2021…”

“…Two parameters are currently being used to measure the resonance, which are the impedance of the system [27][28][29] or the electric current. 30 The measured resonance behavior of the system is then used to tune the excitation frequency of the driving piezoelectric transducer. These state of the art methods of which parameters can be used to implement a FCL are summarized in Table 1.…”

Multichannel Impedance Cytometry Downstream of Cell Separation by Deterministic Lateral Displacement to Quantify Macrophage Enrichment in Heterogeneous Samples

“…[16] Hence, microfluidic separation based on multiple biophysical criteria integrated with on-chip phenotypic analysis at single-cell sensitivity can enhance discrimination of cellular phenotypes and be applied to enrich for minority subpopulations. [17,18,19] This phenotypic information is essential for device design, active control of separation conditions, [20] and sample choice to improve versatility of the workflow [21,22] and discrimination ability of the separation.…”