Direct In-Petri Dish Liquid Droplet Manipulation Based on Microscope and Ultrasonic Phased Transducer Array
Huamin Li, Song LIU
AI summary
Problem
Existing droplet manipulation techniques require chemical additives, specialized hydrophobic surfaces, or risk sample contamination, limiting their compatibility with standard medical and industrial protocols.
Approach
The system uses an ultrasonic phased transducer array to generate an inclined acoustic focal point inside droplets, inducing hydrodynamic forces that move them on standard surfaces, guided by real-time microscope feedback and closed-loop control.
Key results
- Successfully generated an inclined single focal point to actuate droplets without additives or surface treatments
- Achieved stable manipulation across several to tens of microliters by dynamically tuning acoustic pressure
- Closed-loop visual servo control significantly reduced positioning errors compared to open-loop methods
- Validated precise trajectory tracking and positioning for water, oil, and mixed droplets on untreated polystyrene dishes
Why it matters
Enables contamination-free, high-precision droplet handling for life science, biomedical, and industrial applications without requiring specialized surfaces or chemical additives.
Abstract
High-precision liquid droplet manipulation is widely used in life science, biomedical engineering, and industry. However, there still lacks a robotic approach supporting the direct in-petri dish manipulation of liquid droplets without the need of additives (such as magnetic beads) or other setup requirements (such as on hydrophobic or conductive surfaces). From the robotics perspective, this challenge concerns with designing an adequate robot end-effector capable of firmly holding and effectively moving droplet on hydrophilic surfaces. In this paper, we propose an automated robotic system for the direct in-petri dish liquid droplet manipulation based on ultrasonic phased transducer array (UPTA) and microscope, which can interact with users to selectively grasp droplet, follow user designated trajectories to transport droplet, and positioning droplet in high precision. The core working mechanism of the proposed system is to precisely generate an inclined single focal point, acting as a noncontact end-effector, inside the droplet under the guidance of microscope, which can induce sufficient hydrodynamic actuation forces on the peripheral contact line of the droplet to keep the droplet moving along the ultrasonic end-effector. Since it is additive free, our system is inherently compatible to medical, chemical and industrial protocols. Details regarding the system design and implementation, the ultrasound focusing strategy, and the visual servo control scheme are elaborated in this paper. Experiments validated the effectiveness of the proposed system.