Paper-based Microfluidic Chip Customization and Processing

Paper-based microfluidic chips use paper as a substrate instead of materials such as silicon, glass, and polymers. This kind of analysis device is called a micro-lab on paper, also known as a microfluidic paper analysis device. The paper-based microfluidic chip modifies the specific detection area on the surface of the paper-based material through special processing technology to prepare hydrophilic/hydrophobic micro-channels with a certain structure, thereby controlling the movement of the fluid. Paper-based materials have the advantages of good biocompatibility, low cost, simple post-processing, low detection background, and no pollution. They are widely used in clinical diagnosis, food quality, and environmental monitoring.

Material Selection

The fabrication of microfluidic paper chips is the basis for chip detection and analysis. In addition to considering a certain mechanical bearing capacity, it also needs to have good hydrophilic / hydrophobic properties, no significant deformation in the liquid, no chemical reaction with the added reagent, etc. Filter paper has become the substrate material for most paper-based microfluidic chips because of its good water absorption. According to different test substances, different specifications of filter paper or other types of paper can be selected.

Methods for Making Paper Chips

The manufacturing process of paper-based microfluidic chips can be divided into physical-based and chemical-based methods to construct microchannels on paper. The physical process is mainly to construct the designed hydrophobic area on the paper by means of wax-jet printing, laser cutting, printing, drawing, inkjet printing, seal imprinting and so on, so as to make the fluid to be analyzed flow according to the set hydrophilic channel and realize all kinds of biochemical analysis. The chemical process mainly refers to the flow control of analytical samples by constructing the flow channel through lithography, UV curing, plasma etching and so on.

Commonly used materials with curing properties on paper include: wax, SU-8, polydimethylsiloxane (PDMS), polystyrene, alkyl ketene dimer, etc. In addition, three-dimensional microfluidic paper chips can be fabricated by folding or stacking paper chips.

Alfa Chemistry's Paper Chip Fabrication Capabilities

• Fabrication paper chip by printing method

First, the chip pattern is drawn by computer-aided design and drawing software, so that the wax printing part forms a channel to restrict the liquid flow. The design must ensure the completion of sample injection and separation on the chip, a friendly interface with the electrode, avoid spillover after adding samples, and have a certain support strength, so as to achieve a complete chip detection function.

• Ultraviolet Lithography

Ultraviolet lithography has been used in the processing of microfluidic chips for a long time. The photosensitive agent on the filter paper is chemically and physically modified by ultraviolet lithography, and then the photoglue is irradiated by ultraviolet light under the protection of the mask, so that the photoglue is degraded or cross-linked, and a hydrophilic / hydrophobic channel is formed on the filter paper.

In short, Alfa Chemistry's method of making paper chips includes two categories. One is to use physical or chemical means to make the entire paper covered with hydrophobic materials, and then further hydrophilic treatment is performed on all hydrophobic areas through certain technologies. The other type is to carry out hydrophilic or hydrophobic treatment to the part of the filter paper at one time, and directly form microchannels with interleaved hydrophilic and hydrophobic channels.

If you need paper-based chip processing and customized services, please feel free to contact our experts for a free consultation.

References

• Jin, Y.; et al. The Road to Unconventional Detections: Paper-Based Microfluidic Chips. Micromachines, 2022, 13(11): 1835.
• Lu, Y.; et al. Qin and B. Lin, Rapid prototyping of paper-based microfluidics with wax for low-cost, portable bioassay, Electrophoresis. 2009, 30, 1497–1500
• Carrilho, E.; et al. Understanding wax printing: a simple micropatterning process for paper-based microfluidics. Anal. Chem., 2009, 81, 7091–7095
• Schilling, K. M.; et al. Fully enclosed microfluidic paper-based analytical devices, Anal. Chem., 2012, 84, 1579–1585
• Songjaroen, T.; et al. Chailapakul and W. Laiwattanapaisal, Novel, simple and low-cost alternative method for fabrication of paper-based microfluidics by wax dipping, Talanta, 2011, 85, 2587–25933
• Yu, Ling, and Zhuan Zhuan Shi. Microfluidic paper-based analytical devices fabricated by low-cost photolithography and embossing of Parafilm®. Lab on a Chip. 2015;15(7):1642-5.

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