Paper-Based Diagnostic and Environmental Sensors

A simple paper-based sensor in operation to detect two biomarkers: uric acid (purple) and nitrite (pink) for human health monitoring.

Chemical Engineering PhD student Xu Li was unanimously voted as winner of the prestigious international contest at Appita New Speakers Contest on April 22 at the Melbourne Park Function Centre, where she presented her research “Paper-Based Diagnostic and Environmental Sensors”. Appita is the not-for-profit technical association serving the Australian and New Zealand pulp and paper industry. Xu Li is working on developing novel paper-based microfluidic sensors with Dr. Wei Shen in the Australian Pulp and Paper Institute of Department of Chemical Engineering. She presented her novel approach of fabricating paper-based sensors and emphasized the potential of this new technology to the future applications in healthcare, diagnostics and environmental analysis. For example, paper-based sensors can provide rapid and low-cost tests of certain biomarkers for monitoring life style diseases and rapid and quantitative analysis of heavy metals in drinking water. The low cost of this technology makes it particularly useful in improving human health in the developing world. She also emphasized the roles of young scientists and engineers to apply their creativity at the work place to generate innovative ideas which will benefit the society.

Paper has been rediscovered as a unique material for fabricating low-cost diagnostic and environmental sensors. Paper is a porous material made of hydrophilic cellulose fibres. Liquids can penetrate paper driven by capillary force. Paper can also be made hydrophobic by “sizing” treatment; the treated paper resists penetration of aqueous liquids.

At the Australian Pulp and Paper Institute (APPI), researchers engineer complex channels on paper by creating hydrophobic barriers using plasma etching and ink jet printing. The treated paper has well defined hydrophilic channels, liquid sample dosing and detection sites. By introducing biochemical reagents into the detection sites, paper-based sensors are formed. To increase the analytical capability of paper-based sensors researchers have also created on paper functional elements such as valves, separators and reactors. The new approach of Dr Wei Shen’s group for fabricating paper-based sensors was recently highlighted by the leading international scientific journal Lab on a Chip (DOI: 10.1039/b820259c) as novel approach that “has particular significance to miniaturisation research”.