Session: 14-10-01: Micro/Nanofluidics 2025 I

Paper Number: 173664

Additively Manufactured Thin-Film Heater for Continuous-Flow Isothermal Amplification in Microfluidic Systems 

This research presents the development and validation of a compact and energy-efficient DNA amplification platform that integrates a thin-film electro-thermal heater with a serpentine-shaped microfluidic channel. The system is specifically optimized for continuous-flow loop-mediated isothermal amplification (LAMP), enabling precise, efficient, and scalable DNA amplification. It addresses limitations of conventional polymerase chain reaction (PCR), such as bulky equipment, high power consumption, and long processing times, and is designed for portable and low-cost diagnostics in point-of-care (POC) and resource-limited settings. Unlike traditional thin film heaters that rely on complex and costly methods like sputtering or photolithography, this approach uses direct ink writing (DIW) to print 15 µm-thick serpentine-patterned resistive silver heaters directly onto 127 µm-thick polyimide substrates. This method simplifies fabrication, reduces costs, and allows rapid design iteration. A key innovation in this study is the optimized heater layout, which achieves uniform heat distribution across the entire active area which is critical for consistent and reliable DNA amplification. This optimized thermal profile was achieved through iterative design adjustments and validated using infrared thermal imaging combined with MATLAB-based image processing.

 

The silver heater, printed using conductive ink with a volume resistivity below 6.0 × 10⁻⁶ Ω∙cm, reached 65 °C in under 90 seconds with just 2 V input. During a 30-minute continuous run, it maintained a stable mean temperature of 65.9 °C, with a standard deviation of ±1.1 °C and a coefficient of variation of 1.67%, indicating consistent thermal performance. Electrical characterization showed low resistivity (ranging from 0.1 to 0.2 mΩ·mm) and high conductivity (ranging from 3 × 10³ to 6 × 10³ S/mm) across the printed traces. The integrated microfluidic chip, fabricated from COC/COP, includes a serpentine channel that allows the continuous flow of the DNA sample at a rate of 0.4 µL/min, providing a thermal residence time of 30 minutes required for effective isothermal amplification. The continuous-flow LAMP reaction was performed using a colorimetric master mix. Visual results showed a clear pink-to-yellow shift in positive samples, while negative controls remained pink. Gel electrophoresis confirmed amplification specificity and absence of non-specific bands in optimized reactions. Reduced mastermix concentration (1:2 ratio) helped eliminate false positives seen in initial tests. Overall, the system offers precise thermal control, consistent amplification, and rapid visual detection using only 2 V input, making it well-suited for battery-operated diagnostic platforms. This work demonstrates a low-cost, additive-manufactured solution for real-time molecular diagnostics with potential applications in clinical testing, environmental surveillance, food safety, and field-based pathogen detection.

Presenting Author: Shreyas Inamdar Texas State University

Presenting Author Biography: Shreyas Inamdar is a graduate student in Mechanical and Manufacturing Engineering at Texas State University. His research focuses on printed thin-film heaters and microfluidic systems for DNA amplification. He works in the Microsystems and Manufacturing Lab under Dr. Namwon Kim.

Authors:

Shreyas Inamdar Texas State University
Tanzila Kamal Choity Texas State University
Daniel Park Louisiana State University
Hong-Gu Kang Texas State University
Namwon Kim Texas State University