Fabrication of inkjet-printed heaters and application for microfluidic polymerase chain reaction chips

다국어 초록 (Multilingual Abstract)

Inkjet printing deposits the resistive materials to form a patterned heater easily, quickly, and economically in high resolution on paper and flexible substrates, which can convert electric energy to thermal energy when current is applied, based on Joule heating effect. Up to our knowledge, inkjet-printed heater has recently been introduced for nucleic acid amplification test but limited to isothermal amplification with a single heating zone to provide only one constant temperature. Aiming to extend its usage for the conventional polymerase chain reaction (PCR) that requires different temperatures, here we present the fabrication of polyimide film heaters using Dimatix inkjet printer with aqueous conductive silver nanoparticle ink. For that, firstly we optimized the ink, design and printer setting to attain high consistency of heater quality. After thermal annealing at 250 oC, we characterized the material, electrical, and thermal properties of the printed heaters. To maintain durability when a high electrical load of current was applied, it was important to keep the number of printing layers at three. A typical U-shape heater, of which the average end-to-end resistance was at 28.166 +/- 0.893 Ohm in case of 0.40 mm / 0.40 mm stroke weight ratio of heating regions, had been investigated. For PCR application, we proposed a four-heating-zone system with two interdigitated U-shape heaters whose stroke weight ratios were 0.45 mm / 0.35 mm, and 0.45 mm / 0.25 mm, after optimization. Target temperatures were obtained after 15 min when using with a temperature controller. This four-heating-zone system could maximize the number of thermal cycles on a limited area of PCR chip when we combined with corresponding flow channel design. By using xurography, we had prototyped a continuous flow microfluidic device with polydimethylsiloxane (PDMS) 5:1 for testing efficiency of our four-heating-zone system and set up a platform to measure, control, and analyze the result of PCR amplification.

목차 (Table of Contents)

• 1. Introduction 1
• 2. Experimental details 3
• 2.1 Materials 3
• 2.2 Effect of ink, pattern design and printer setting 3
• 2.3 Heater design and fabrication 4
• 2.4 Characterization of printed heater 5
• 2.5 Design and fabrication of PDMS-based flow channels 6
• 2.6 Surface modification and characterization of flow channel 8
• 2.7 Device assembly and operation 8
• 2.8 DNA amplification test 9
• 2.9 Gel electrophoresis 10
• 3. Results and discussion 11
• 3.1 Effect of ink, pattern design and printer setting 11
• 3.2 Material characterization of printed heater 13
• 3.3 Electrical and thermal performance of printed heater 14
• 3.4 Optimization of heater design 16
• 3.5 PDMS flow channel characterization 18
• 3.6 Flow in PDMS channel 19
• 3.7 PCR amplification test 20
• 4. Conclusion 22
• References 23