Application Cases

Experiment Name: Characterization of Microdroplet Properties in a High-Voltage Amplifier Droplet Microfluidic Chip System and Application in Amino Acid Detection

Microfluidic Chip System (Microfluidics): A microfluidic chip system, or lab-on-a-chip, integrates basic operation units such as sample preparation, reaction, separation, detection, cell culture, sorting, and lysis—common in chemistry and biology—onto a chip of just a few square centimeters (or even smaller). It forms a network of microchannels through which a controlled fluid flows,贯穿 (贯穿,贯穿) the entire system. Current microfluidic chip systems mainly include continuous microfluidic systems and droplet microfluidic systems.

Research Direction: Research on microfluidic chip systems based on droplet microfluidics

Experimental Content:
Because microbial screening experiments often require long periods, higher demands are placed on microdroplets in microfluidic chips. These include improving microdroplet stability, optimizing biocompatibility, and preventing the leakage of aqueous phase substances from within the microdroplets into the oil phase. Addressing these issues, this study focuses on metabolites (amino acids). By investigating the characteristics of picoliter-scale microdroplets encapsulating amino acids, it lays the foundation for amino acid detection, high-throughput screening of corresponding production strains, and directed evolution using droplet microfluidic chip systems.

Testing Equipment:
Laser, focusing objective, high-speed camera, filter, photomultiplier tube (PMT), data acquisition card, high-voltage amplifier, Mitos pressure pump, silicon wafer, SU-8 2025 photoresist, plasma cleaner, spin coater, hot plate, UV lithography system, microfluidic chip, PDMS

Experimental Procedure: Construction of the Integrated Droplet Microfluidic Chip Control System

A laser emits light at a wavelength of 532 nm. The emitted laser light passes through a filter to remove stray light components and is then focused onto the detection point of the microfluidic chip. When microdroplets encapsulating a fluorescent substance pass through the detection point, they are excited and emit fluorescence. The fluorescence is focused by the focusing objective lens and directed to a beam splitter. The beam splitter directs a portion of the fluorescence to a high-speed camera for实时 (实时, real-time) monitoring of microdroplet flow. The other portion of the fluorescence passes through a filter and is received by a photomultiplier tube (PMT), which converts the fluorescence signal into a voltage signal. The data acquisition card then acquires this signal, and it is analyzed by LabVIEW software. The high-voltage amplifier is used for microdroplet deflection. When the detected signal of a target microdroplet exceeds the sorting threshold, the analysis software applies a deflection voltage to the microdroplet via the power amplifier and electrodes on the microfluidic chip. Due to the dielectrophoretic force, the target microdroplet is deflected, flows into the sorting channel, and is collected.

Test Results:

1. The generated microdroplets have controllable diameters, uniform size, and good stability. The reaction system within the microdroplet is small, conserving significant amounts of reagents.

2. Microdroplets can remain stable for extended periods, meeting the time requirements for reagent reactions or cell culture.

3. The encapsulated substances within the microdroplets remain stable, and there is no cross-contamination between microdroplets. This does not affect subsequent fluorescence detection and sorting of the microdroplets.

4. The sorting throughput of microdroplets can reach up to 600 per minute. These experiments provide the possibility of high-throughput screening for the detection and analysis of cell secretions such as enzymes and amino acids, as well as the screening of corresponding production strains. This lays the foundation for the application of droplet microfluidic chips in directed evolution.

Figure: Specifications of the ATA-7010 High-Voltage Amplifier