Rapid-release reversible bonding of PMMA-based microfluidic devices with PBMA coating.

PMMA-based microfluidics have been widely used in various applications in biological and chemical fields. In the fabrication process of PMMA-based microfluidics, the substrate and cover plate usually need to be bonded to enclose the microchannel. The bonding process could be permanent or reversible. In some application scenarios, reversible bonding is needed to retrieve the samples inside the channel or reuse the chip. Current reversible bonding methods for PMMA-based microfluidics usually have drawbacks on bonding strength and contaminations from the adhesives used in the bonding process. In this study, a new approach is proposed for the reversible bonding of PMMA-based microfluidics, a layer of PBMA (with a very similar structure to PMMA) was coated on the surface of PMMA and then use the thermal fusion method to achieve the bonding with a high bonding strength, a tensile bonding strength of around 0.8 MPa was achieved. For debond process, a rapid temperature drop will trigger the immediate release of the bonding within several seconds. Detailed bonding strength measurement and biocompatibility tests were also conducted in this study. The proposed bonding method could have wide application potential in the fabrication of PMMA-based microfluidics.

Assessment of microplastics using microfluidic approach.

Microplastics are plastic particles smaller than 5 mm, and microplastics have gradually become a severe environmental pollution source that exists in the atmosphere. The identification and quantification of microplastic particles are challenging, current approaches require expensive instruments and are usually time-consuming. In this study, a microfluidic method was introduced to detect and count microplastics using a polymer-based microfluidic chip. Microplastic particles were stained with Nile red, dispersed in the carrier fluid and passed through the microchannel. A fluorescence microscope filmed the whole process as microplastic particles passed through the microchannel. Finally, the software automatically analyzed the video footage for the microplastic particle counting and size analysis. The entire process is fully automated for microplastic particle counting and is much more efficient than the current manual counting method. The proposed study may have broad application potentials in the environmental field.

Ultra-low-cost fabrication of polymer-based microfluidic devices with diode laser ablation.

In this work, a diode laser ablation approach was used for the fabrication of PMMA-based microfluidic devices. Compared with the conventional CO2 or femtosecond laser fabrication method, the proposed laser ablation method based on diode laser significantly lowered the cost in the fabrication of polymer-based microfluidic devices with comparable resolution and surface quality. PMMA substrate was used for the laser ablation process, due to the transparency of PMMA in the diode laser's working wavelength, a layer of Kraft tape was applied on the surface of PMMA for the absorption of laser energy, and microchannels were then achieved on the surface of PMMA with the proposed low-cost diode laser system. The comparison between the proposed method and the CO2 laser ablation method was also conducted in this study. The profile of the fabricated microchannels was carefully characterized, several microfluidic devices were also fabricated for the demonstration of the proposed fabrication method using a diode laser.

Integrated sample processing and counting microfluidic device for microplastics analysis.

BACKGROUND: The presence of microplastics is widespread in the ocean, freshwater, soil, or even in the human body. The current microplastics analysis method involves a relatively complicated sieving, digestion filtration, and manual counting process, which is both time-consuming and requires experienced operation personnel. RESULT: This study proposed an integrated microfluidic approach for the quantification of microplastics from river water sediment and biosamples. The proposed two-layer PMMA-based microfluidic device is able to conduct the sample digestion, filtration and counting processes inside the microfluidic chip with the preprogrammed sequence. For demonstration, samples from river water sediment and fish gastrointestinal tract were analyzed, result indicate the proposed microfluidic device is able to perform the quantification of microplastics from river water and biosamples. SIGNIFICANCE AND NOVELTY: Compared with the conventional approach, the proposed microfluidic-based sample processing and quantification method for microplastics are simple, low-cost and with low demand for laboratory equipments, the self-contained system also has the application potential for the continuous on-site inspection of microplastics.