Empowering agriculture: rapid on-site soil nutrient detection with microfluidic colorimetry

This study introduces a novel methodology for the microfluidic colorimetric detection of soil analytes, offering enhanced efficiency for assessing plant growth parameters. Microfluidic channels (μPADs) were fabricated on paper substrates using a customized XY-Plotter equipped with a technical drawing pen containing an optimized polydimethylsiloxane (PDMS)-hexane solution, imparting hydrophobic properties to the substrate. The developed μPADs enabled visual detection of zinc concentrations ranging from 1 mg dL⁻¹ to 45 mg dL⁻¹ and orthophosphate concentrations from 0.5 g dL⁻¹ to 8 g dL⁻¹ in artificial soil (Hoagland's solution) through the formation of distinct colorimetric complexes. The calculated limits of detection (LOD) for zinc and orthophosphate were 0.0107 g dL⁻¹ and 1.24 g dL⁻¹, while the limits of quantification (LOQ) were determined as 0.035 g dL⁻¹ and 4.1 g dL⁻¹, respectively. The approach demonstrated high selectivity and sensitivity, providing rapid and reliable insights into the soil's nutrient profile. Compared to conventional methods, this innovative sensing platform is faster, cost-effective, and well-suited for on-site analysis of soil micro- and macronutrients. This advancement holds significant potential for agricultural practitioners, enabling informed decision-making to optimize soil fertility and support sustainable agricultural practices.