Nucleic acid amplification is a critical step in many diagnostic workflows from clinical to point-of-care settings. Microfluidics offers miniaturized platforms for handling small sample volumes; however, heat-assisted bioreactions such as digital loop-mediated isothermal amplification (dLAMP) are challenging to implement in poly(dimethylsiloxane) (PDMS)-based devices due to the material's intrinsic porosity and hydrophobicity. The porosity of this polymer network promotes evaporation of the reaction solution and diffusion of small molecules, while its surface hydrophobicity encourages biofouling, leading to loss of enzymatic activity. In this work, we present a facile and straightforward strategy to overcome these problems that avoids additional fabrication steps, specialized materials, or complex post-fabrication treatments. First, the porosity of PDMS was tuned by altering the conventional monomer-to-cross-linker ratio, resulting in significant retention of solution volume even after 2 h of heating at 60 °C and a 70% reduction in small-molecule loss via diffusion into the polymer network. Second, to render the PDMS surface hydrophilic, a dry coating of the commercially available surfactant, Tween-20 was employed. The results indicate that the dry coating enhances amplification efficiency, whereas incorporating the same amount of surfactant directly into the reaction solution reduces efficiency. Through this combined approach, we demonstrate a twofold improvement in the limit of detection for nucleic acid amplification by dLAMP, greater uniformity in reaction volumes across the array, and more robust performance—improvements that are retained even after 8 months of device storage. By addressing key material limitations, this study advances PDMS-based microfluidics as a practical platform for high-precision nucleic acid quantification.
Rathnaweera et al. (Fri,) studied this question.