Single cell analysis is a key tool for analyzing cellular heterogeneity in the fields of disease diagnosis and biomedical research. Traditional single-cell analysis methods, such as optical microscopy or flow cytometry, are often limited by complex operations, high costs, or strong invasiveness, making it difficult to meet the research needs of high-throughput and high-sensitivity. Impedance and dielectric spectroscopy (IDS) technology, as a non-invasive, real-time monitoring, and high-throughput potential method, has become an important technological path for single-cell analysis. The principle is that when cells or particles pass through the electrodes in microchannels, they will disturb the electric field and generate electrical signals corresponding to their own electrical characteristics and spatial positions. However, in non-uniform electric fields, if particles deviate in the vertical direction, it will significantly affect the symmetry of the electric field distribution, resulting in signal amplitude distortion and reducing the accuracy and repeatability of detection.

To solve this problem, fromThe joint research team of the University of Manchester and the University of Melbourne has designed a 3D printed microfluidic chip with integrated nozzle structure, which can realize adjustable 3D hydrodynamic focusing through two-stage sheath flow.This study aims to“Precision flow focusing in 3D printed microchannels for enhanced impedance spectroscopy”Title, published in an international journal《Sensors and Actuators B: Chemical》Up there.

The core of this innovative microfluidic chip lies in its unique nozzle structure, which can actively lift the sample flow above the bottom of the microchannel, effectively avoiding non-specific interactions between particles and the channel wall. By combining the top-down sheath flow constraint and the focusing effect of the downstream contraction segment, the system achieves three-dimensional precise positioning of particles passing through the sensing area.The key manufacturing technologies for achieving this complex three-dimensional structure are Mofang Precision's surface projection micro stereolithography (P μ SL) technology and composite precision photopolymerization 3D printing technology.The research team adoptsMofang Precision microArch ® The D1025 (precision: 10&25 μ m) 3D printing system, using HTL resin as the material, successfully molded a multi-scale integrated microfluidic chip containing a 120 μ m radius nozzle, an 800 μ m wide main channel, and a 100 μ m wide contraction segment in one go.

As shown in Figure 1, by adjusting the flow ratio Q2/Qt, particles can be precisely pushed towards the electrode without relying on shallow channels or complex electrode configurations. This tunability enables the system to adapt to different application scenarios, from cell analysis to chemical detection, exhibiting excellent adaptability.

Furthermore, Figure 2 provides a detailed explanation of the mechanism of three-dimensional fluid focusing. The system adopts a three-stage focusing strategy: firstly, the sheath flow F1 is combined with the nozzle to achieve lateral and partial vertical focusing; Secondly, the top sheath flow F2 enhances vertical constraint; Finally, the downstream contraction segment consolidates the overall focus effect. This configuration ensures that particles always approach the coplanar electrode when passing through the sensing area, thereby optimizing signal acquisition.

The research team validated the focusing efficiency through fluorescence imaging and impedance spectroscopy experiments. Figure 3 shows the simulation results, revealing the influence of microchannel structure on fluid dynamics. When the flow ratio Q1/Qs changes from 0.99 to 100, the focusing width can be adjusted between 0.07 and 0.65 times the channel width, reflecting the adjustability of height. At the same time, vertical focusing was quantified by confocal microscopy, and it was shown that at Q2/Qt=0.9, the distance between particles and electrodes could be reduced to below 10 μ m, significantly improving signal quality.

The experimental part uses fluorescent microspheres as the model system, and under the condition of a fixed total flow rate of 100 μ L/min, particle localization is achieved by adjusting the sheath flow ratio. The fluorescence imaging results in Figure 4 visually present the effects of lateral and vertical focusing. As Q2/Qt increases, the height of the particle flow gradually decreases and the width slightly increases, but the contraction area effectively offsets this diffusion, ensuring that particles remain tightly clustered in the sensing area. This design achieves a dynamic range of focal flow sizes from 71 × 70.5 to 121 × 10.95 μ m in a 300 μ m channel, suitable for various particle sizes.

In electrical characterization, the amplitude of impedance signal varies with the vertical position of particles, and the simulated and experimental data are highly consistent. Figure 5 shows the measurement settings and results. When Q2/Qt=0.9, the signal-to-noise ratio reaches a peak of 17.38 dB and the signal variability is low. Statistical analysis shows significant differences among all traffic conditions, highlighting the importance of optimizing vertical focus. This discovery provides a reliable foundation for impedance cytometry, enabling high-precision detection without relying on complex post-processing.

In this study, the high-precision manufacturing capability of Mofang Precision enables complex nozzle structures and contraction areas to be formed in one go, avoiding the complex alignment and bonding steps required by traditional multi-layer lithography technology. This not only simplifies the manufacturing process, but also enhances the overall integrity and functional integration of the device, providing geometric flexibility and rapid prototyping verification capabilities for the design of microfluidic chips.

As a dual precision microArch of Mofang Precision's high-tech level®The Dual series devices (D0210, D1025) have innovatively achieved switching printing of different accuracies on the same layer (XY axis direction) and different layers (Z-axis direction), while still maintaining ultra-high precision and tolerance control capabilities. The new automatic level adjustment system makes industrial grade 3D printing smarter, more stable, and more efficient. In terms of printing scale, this series has achieved cross scale precision machining capability from 2 μ m to 100mm × 100mm × 50mm, breaking through the collaborative limitations of traditional manufacturing in terms of size and accuracy. In the field of rapid prototyping, this capability is applicable to biomedicine, precision electronics5GInnovative research and development in high-precision industries such as communications and semiconductors provide a new solution that combines high-speed response, flexible iteration, and significant cost reduction and efficiency improvement.

As precision medicine moves towards a new stage of personalized diagnosis and treatment, Mofang Precision continues to increase its research and development investment, committed to promoting the evolution of micro nano 3D printing technology to a higher level. In the future, Mofang Precision will play a key role in a wider range of cutting-edge fields by providing precision manufacturing solutions that combine ultra-high precision and highly customized capabilities. From personalized medical equipment to customized sensors, from micro optical components to microfluidic systems, Mofang Precision will provide critical support for scientific research exploration and industrial upgrading.