UCLA researchers have developed a pulsed-laser triggered microfluidic switching mechanism capable of sub-100 µs switching (e.g. ~70 µs), enabling ultrafast cell/particle sorting in a microfluidic fluorescence-activated cell sorting (µFACS) platform using cavitation bubbles rather than mechanical valves.
Flow cytometry and FACS are key tools in biology and medicine for sorting cells by fluorescence or other markers. Traditional droplet-based FACS systems are bulky, require open fluidics, high voltages, or mechanical parts, and may generate aerosols or damage cells. Microfluidic FACS attempts to miniaturize and enclose the process, but existing microfluidic switching (e.g. pneumatic valves, electrokinetic flows) are slow (hundreds of µs to ms), limiting throughput. There is a need for a fast, safe, compact, high-throughput switching mechanism compatible with microfluidic chips.
The switch uses a focused pulsed laser to induce a cavitation bubble adjacent to a microfluidic bifurcation. The rapid expansion of the bubble displaces fluid, deforming channel walls or injecting a micro-jet to redirect the trajectory of nearby particles/cells from one flow path to another.
By timing the bubble formation precisely after detecting a target particle or cell (e.g. via fluorescence), the system can sort individual particles into a “collection” channel rather than waste.
The design is compatible with single-layer PDMS microfluidic chips (no complex multi-layer valves required).
The switch is designed such that cells are shielded from direct impact of the bubble expansion/collapse, minimizing shear or stress damage.
The mechanism supports very high sorting speeds (greater than 10,000 cells/sec in some embodiments), significantly improving over prior microfluidic switches.
Extremely fast switching (on the order of 70 µs or potentially faster).
Compact and chip-integratable (compatible with PDMS microfluidics).
No mechanical moving parts, eliminating many failure modes and enabling high reliability.
Enclosed fluidics reduce aerosolization risk, improving biosafety.
High viability of sorted cells due to minimal mechanical stress.
Scalable to multiple switches or parallel channels.
High-throughput microfluidic FACS modules in lab-on-chip devices.
Cell sorting for diagnostics, single-cell genomics, immunology, or circulating tumor cell (CTC) isolation.
On-chip sample preparation and sorting in integrated workflows (e.g. sorting → lysis → PCR).
Portable or point-of-care cytometry systems where compactness and safety are key.
Research platforms for rare cell detection, cell phenotyping, and personalized medicine.
T. -H. Wu, Y. Chen, S. -Y. Park and E. P. -Y. Chiou, "Pulsed laser triggered high speed microfluidic fluorescence activated cell sorter," CLEO: 2011 - Laser Science to Photonic Applications, Baltimore, MD, USA, 2011, pp. 1-2. https://ieeexplore.ieee.org/document/5950207