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Laser-Direct-Write (LDW) Technologies for Biomedical Applications

Paper-based microfluidic sensors

Learn how we apply this technique to create point-of-care diagnostics.

Point-of-care (POC) diagnostics are specifically targeted at medical testing at or near the site of the patient’s care, without further need for specialist laboratory environment and trained personnel. Such POC testing is facilitated through the use of uncomplicated, user-friendly and portable testing devices and much effort has been directed towards producing diagnostic test-kits that are not only smaller, faster and smarter, but also satisfy the elusive goal of being cost-effective – a vital requirement that ensures economic viability, since such POC test procedures may need to be performed repeatedly over potentially very large sample groups, that could even extend to an entire nation in the case of a pandemic. 

Paper with its varied characteristics, is now considered as a highly suitable alternative for fabrication of lab-on-chip (LOC) type POC devices, and many labs have focused their attention on this direction. In recent years, paper based POC devices have been thoroughly researched and rapidly developed, especially for medical diagnostics and biochemical analysis. This is because of the urgent need for reliable diagnostic tools in developing countries where there is a lack of infrastructure, of trained personnel and people within such countries cannot afford expensive technologies.

Compared with the polymer, silica or silicon-based microfluidic devices, paper-based devices offer considerable advantages. First, paper is readily available in a range of different forms and grades, which exhibit a range of different properties, such as porosity, wettability and its wick ability. In addition, it is cheap and biocompatible, which makes it suitable for implementation of simple biological assays. Furthermore, paper is widely manufactured from renewable resources and can be easily stored and transported and it is also biodegradable and can be incinerated. Finally, an important feature that makes paper very attractive for microfluidic devices is its inherent ability to wick fluids via capillary forces, which avoid the need for external pumps which are necessary for the case of microfluidic devices on other above-mentioned platforms. 

As their name suggests, paper-based microfluidic devices normally consist of interconnected hydrophilic fluidic channels, which are demarcated by the hydrophobic walls, to guide and transport an analyte fluid, from a point of entry on the device to a reaction zone that has been pre-treated with specific reagents. Unlike glass, silicon or polymer substrates, where the fluidic channels are surface-relief structures that have been inscribed in these substrates, for paper-based devices the fluidic channels are formed inside and extend throughout the full thickness of the paper.