Session: 13-02-01: Design and Fabrication, Analysis, Processes, and Technology for Micro and Nano Devices and Systems

Paper Number: 149364

149364 - Direct Ink Writing of Silver Heaters for On-Chip Isothermal Amplifications 

Additive manufacturing of electrothermal heaters allows for intricate patterning of thin film heaters suitable for on-chip DNA amplification. These printed heaters can be easily integrated into microelectromechanical systems (MEMS) and lab-on-a-chip technologies to achieve precise temperature control. Motivated by the demand for deployable diagnostic devices, our printed thin film heaters provide rapid heating and uniform temperature areas, essential for temperature-dependent reactions, while minimizing thermal inertia and uneven heating. The heating capability of these heaters significantly reduces energy consumption, aligning with sustainable technology goals. Moreover, the flexible design and patterning of electrothermal heaters using additive manufacturing support a variety of engineering applications, enhancing the versatility and scalability. Flexible electrothermal heaters printed on polyimide (PI) substrates have gained attention for their application in wearable electronics and biological application due to their flexibility, high heat resistance, and low thermal expansion coefficient. The effectiveness of these heaters is evaluated based on the voltage needed to reach specific temperatures and the uniformity of heat distribution. This study focuses on improving these factors to enhance the performance and feasibility of printed thin film electrothermal heaters for isothermal amplification applications.

 

We developed a miniaturized electrothermal heater that effectively facilitates the isothermal amplification of deoxyribonucleic acid (DNA) on a portable and compact platform. Single-layer thin film silver heaters of 5 µm thickness was printed using a direct ink writing (DIW) printer. The serpentine-shaped printed heater, with a total length of 47.3 mm, was incorporated with a 50 µL PMMA chamber to regulate the process temperature for biochemical reactions. The heaters showed the ability to increase the water temperature inside the chamber to 90 °C within 20 seconds, using a voltage input as low as 4 volts. Additionally, the printed heater effectively maintained the required temperature of 65 °C for isothermal amplification for one hour and provided a uniform distribution of thermal energy across the entire chamber area, ensuring consistent DNA amplification. The uniformity of heat distribution by the heater was analysed through images taken by an IR camera using the image processing functions of MATLAB. The resistivity of the DIW-printed heater was measured at 1.41 ± 0.03 × 10^-6 Ω·m, indicating improved conductivity because of the increased thickness of the single-layer DIW-printed heater. The functionality of the amplification platform was validated by comparing a plasmid DNA (pDNA) sample digested by EcoRI enzyme at 37 °C for 4 hours on our platform with the same pDNA sample digested in a conventional thermal bath under the same conditions. Gel electrophoresis results showed identical findings for both samples, confirming the effectiveness of the fabricated heater. This study is a notable advancement in electrothermal heaters for portable isothermal amplification platforms, showing potential applications in molecular biology and diagnostics, particularly for rapid and scalable point-of-care testing.

Presenting Author: Shreyas Inamdar Texas State University

Presenting Author Biography: Mr. Inamdar is as graduate student at Texas State University.

Authors:

Shreyas Inamdar Texas State University
Alireza Sargordi Texas State University
Tanzila Choity Texas State University
Anahita Emami Texas State University
Hong-Gu Kang Texas State University
Gwan-Hyoung Lee Seoul National University
Namwon Kim Texas State Univeristy