Paper-based microfluidic diagnostics hold promise as a low cost platform for disposable tests. First invented and popularized by the Whitsides lab (see Paper-based Diagnostic Microfluidic Devices), this genre of technology treats paper with a special hydrophobic polymer to create small channels that route fluid any which way via capillary action. With this ability, a tiny square of paper can be used to direct a drop of fluid (blood, etc) through various paths, and at the end of each, a diagnostic test can be performed on the fluid through interaction with a reagent (generally antibody based).
New research reported in the online edition of Advanced Materials promises to extend the functionality of paper-based diagnostics through incorporating high resolution metallic resonators, potentially enabling label-free quantitative analysis of substrates. To test their technology, Dr. Hu Tao and others from Tufts and Boston University soaked their paper with glucose solutions at various concentrations and were able to note capacitance changes in metamaterial, producing a progressively lower resonance with increasing glucose concentration.
Shaving away the jargon, Dr. Tao and team were able to detect varying glucose concentrations strictly based on electromagnetic properties of the paper, without any sort of chemical reaction.
While most paper-based biosensors – usually a strip of paper doped with an antibody specific to an antigen of interest – use colorimetric readout and detect the color or intensity change in the visible range, metamaterials offer a broader operating range, covering from radio frequency to optical wavelengths. These patterned papers offer more opportunities for multiplexed and quantitative analysis.
“In our device, paper acts as the dielectric substrate providing both support and a material to sample and embed analytes which then modulate the resonance of the split-ring resonators that compose the metamaterials,” explains Omenetto. “This offers additional utility in the signal transduction capabilities and provides the possibility to explore label-free sensing strategies based on electromagnetic modulation.”
Nanowerk: Paper-based Metamaterial Biosensor…