Self-Focused Acoustically Driven pL-Level Dispensing Pipet Enabling Rapid Concentration Gradient Generation

Precise construction of concentration gradients is critical in biomedical research, drug screening, and toxicological analysis. Traditional methods, such as serial dilution and multichannel pipetting, are operator-dependent and often suffer from limitations, particularly when handling small volumes. These issues become more pronounced in high-throughput and microscale experimental models, where even minor inaccuracies can compromise experimental reproducibility. To address these challenges, we introduce a gigahertz (GHz) self-focused acoustic dispensing pipetting (ADP) technology that enables high-precision, on-demand droplet dispensing with enhanced reproducibility and efficiency. Operating at GHz frequencies, this system uses self-focused acoustic energy to generate ultrafast microdroplet dispensing cycles with a coefficient of variation (CV) below 1%, ensuring precise volume delivery. The technology achieves high throughput (6 μL/s) and rapid droplet ejection velocities (exceeding 2 m/s), enabling the formation of concentration gradients in under a minute. We demonstrate the potential of this technology for applications in antimicrobial susceptibility testing (AST), where precise gradients of antibiotics (ampicillin) are generated to determine the minimum inhibitory concentration (MIC) in bacterial cultures. The ADP system outperforms traditional pipetting methods in terms of gradient fidelity (R² = 0.997) and operational efficiency, offering significant improvements in reproducibility and throughput. Furthermore, the ADP platform facilitates versatile applications in high-throughput drug screening and personalized medicine by enabling single-step, microvolume gradient construction.