A low-cost microwave metamaterial-inspired sensing platform for quantitative paper microfluidic analytical devices

The medical field and public health rely on diagnostics carried out by sensors and laboratory testing methods. However, conducting laboratory tests is a demanding task, requiring both substantial equipment and the skilled touch of experienced operators. The microfluidic field has tackled this challenge over recent years. Paper microfluidic devices have become popular recently due to their testing speed, low cost, and accessibility. They are more suitable for field operations and developing regions with limited access to centralized healthcare centers and medical laboratories since they do not require external flow control instruments and are much cheaper to make when compared to conventional microfluidic chips. However, the majority of paper-based analytical devices tend to be qualitative or semi-quantitative; consequently, there is a significant need for paper-based quantitative transduction methods, given their expanding range of applications. Here, we introduce a novel microwave paper-based metamaterial-inspired transduction method that relies on dielectric sensing. Using paper as both the microfluidic channel and the resonator substrate hugely reduces the sensing device’s costs, complexity, and environmental impact. We designed the metamaterial-based transducer using computational methods and demonstrated its fabrication and operation experimentally. Dielectric sensing of multiple analytes with different permittivities is demonstrated as a proof of concept. Although the device has a non-linear response curve in a wide range of permittivity change, the response can be assumed linear in the shorter spans. The results for permittivities lower than 30 show a 2.14 MHz/RPU sensitivity. This design is a prototype demonstrating the possibility of integrating a porous media microfluidic channel and paper-based microwave resonators. The linear sensing performance illustrated by the platform indicates its potential applications in the biosensing field.