Hybrid femtosecond laser fabrication of a size-tunable microtrap chip with a high-trapping retention rate

Microfluidic Approaches for Microactuators: From Fabrication, Actuation, to Functionalization

Microactuators can autonomously convert external energy into specific mechanical motions. With the feature sizes varying from the micrometer to millimeter scale, microactuators offer many operation and control possibilities for miniaturized devices. In recent years, advanced microfluidic techniques have revolutionized the fabrication, actuation, and functionalization of microactuators. Microfluidics can not only facilitate fabrication with continuously changing materials but also deliver various signals to stimulate the microactuators as desired, and consequently improve microfluidic chips with multiple functions. Herein, this cross-field that systematically correlates microactuator properties and microfluidic functions is comprehensively reviewed. The fabrication strategies are classified into two types according to the flow state of the microfluids: stop-flow and continuous-flow prototyping. The working mechanism of microactuators in microfluidic chips is discussed in detail. Finally, the applications of microactuator-enriched functional chips, which include tunable imaging devices, micromanipulation tools, micromotors, and microsensors, are summarized. The existing challenges and future perspectives are also discussed. It is believed that with the rapid progress of this cutting-edge field, intelligent microsystems may realize high-throughput manipulation, characterization, and analysis of tiny objects and find broad applications in various fields, such as tissue engineering, micro/nanorobotics, and analytical devices.

Rapid trapping and tagging of microparticles in controlled flow by in situ digital projection lithography

Real-time and fast trapping and tagging of microfeatures, such as microparticles and cells, are of great significance for biomedical research. In this work, we propose a novel in situ digital projection lithography technology that integrates real-time, in situ generation of digital masks for particle processing and fluid control into conventional DMD-based projection lithography. With the help of image recognition technology, we rapidly resolve the information of the microparticle profile or channel location, combining the selection of existing masks of different shapes, thus enabling in situ generation of user-customized micro-trap arrays and microfilter arrays for particle trapping and tagging. The success in trapping and filtering single particles, particle arrays, and cells has indicated the promising prospects of this novel technology for broad applications in microfluidics, single-cell analysis, and early-stage disease diagnostics.

Real-time capture of single particles in controlled flow by a rapidly generated foci array with adjustable intensity and pattern

We propose a new, to the best of our knowledge, technique to capture single particles in real-time in a microfluidic system with controlled flow using micro-pillar traps fabricated by one-step. The micro pillars are fabricated in parallel by femtosecond multi-foci laser beams, which are generated by multiplexing gratings. As the generation process does not need integration loops, the pattern and the intensity distribution of the foci array can be controlled in real-time by changing the parameters of gratings. The real-time control of the foci array enables rapidly fabricating microtraps in the microchannel with adjustment of the pillar spaces and patterns according to the sizes and shapes of target particles. This technology provides an important step towards using platforms based on single-particle analysis, and it paves the way for the development of innovative microfluidic devices for single-cell analysis.

Circular cross section waveguides processed by multi-foci-shaped femtosecond pulses

We developed a simple multi-foci-shaped femtosecond pulsed (MFSFP) method for processing circular cross section waveguides in transparent materials. With this flexible processing method, the focus energy distribution can be designed freely and arbitrarily, and single-mode waveguides with cross section circularity better than 96.0% were achieved. The mode shape difference (1.93%) of circular waveguides is smaller than the difference (7.01%) of normal elliptical waveguides. The coupling abilities of the two kinds of waveguides were investigated with three-dimensional (3D) directional couplers in both experiments and theoretical simulations. The coupling coefficient difference of circular waveguides in vertical and horizontal coupling directions was ∼0.01mm^-1, which was smaller than 0.33mm^-1 of normal waveguides. The circular symmetric waveguides will play an important role in large-scale high-intensity 3D photonic integrated circuits.