Microheaters for flexible electronics: establishing basic design guidelines towards low power, high uniformity devices

Miniaturized heating platforms, i.e., microheaters, are nowadays necessary for many applications, such as gas sensing, wearable technology, and DNA amplification. These heaters can be based on a wide variety of designs (e.g., meander, spirals, arrays of lines) and materials (e.g. platinum, gold, silver, titanium).  Among them, Pt is one of the most extensively studied materials due to its low power consumption and high electrical conductivity. For heater power consumption to be efficient, heaters must be thermally insulated, avoiding heat losses and maintaining uniform heat in the desired area. In this regard, an appropriate candidate as a result of its low thermal conductivity is polyimide (PI), which also benefits from chemical stability and flexibility. Although advances in the field of micro heaters are growing rapidly in the literature, studies covering comprehensive design comparisons for the development of optimal heaters are still lacking. Furthermore, the characterization of heaters is often very limited, as the contributions of each heat transfer mechanism (radiation, convection, and conduction) are often ignored. If considered, however, parameters are assumed from books, previous work, or taken by comparison with simulations, which often leads to considerable errors since the experimental conditions are rarely the same.

In this project, the student will learn how to fabricate PI-insulated Pt microheaters employing some of the most commonly used techniques in microelectronics, such as photolithography and physical vapor deposition. These heaters will consist of a wide variety of designs, from which the student will systematically extract and compare the electrical and thermal characteristics of each, paying special attention to uniformity and power consumption. Going further, the student will participate in determining experimentally the heat contributions of the heaters and will contrast the results obtained with Finite Element Method (FEM) simulations. Combining these results, the student will be able to establish significant guidelines for the rational design of uniform, low-powered microheaters. Depending on the motivation of the student, the research can be further extended to the scrutiny of more modern materials, such as TiN.