Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee Accelerated publication Low-power printed micro-hotplates through aerosol jetting of gold on thin polyimide membranes S. Khan a, ⁎ , T.P. Nguyen b , M. Lubej a , L. Thiery b , P. Vairac b , D. Briand a a Ecole Polytechnique Fédérale de Lausanne, Soft Transducers Laboratory, Neuchâtel, Switzerland b FEMTO-ST Institute, UMR 6174, Université de Franche-Comté, CNRS, ENSMM, UTBM, France ARTICLE INFO Keywords: Aerosol jet Printing Flexible Micro-hotplate Gold ABSTRACT We report on patterning of miniaturized gold (Au) based micro-hotplates reaching high temperature at lower power consumption than ever reported using aerosol jet printing. Efficient heating (i.e. ~12 °C/mW) was achieved by reducing the effective heating area and the thickness of the polyimide substrate. Au nanoparticles solution was used for printing heaters of two different sizes, i.e. 500 × 500 μm 2 and 150 × 150 μm 2 . These double meander heaters were patterned on a 50 μm-thick polyimide substrate implementing 5 μm-thick mem- branes using laser etching. Finite element simulations were used to optimize the thermal design of the devices. They exhibit a power consumption at 250 °C of 39 mW and 22 mW for the larger and smaller heater design, respectively. These results indorse the significance of aerosol jet printing process at high resolution to realize high temperature and power efficient micro-hotplates on foil for applications such as; in portable gas and chemical sensors, thermal metrology and mapping, localized heating, thermal actuators and microfluidics etc. 1. Introduction Printing electronic devices on polymeric substrates have witnessed significant growth in recent years, with keen interest in developing cost-effective manufacturing routes and processing of diverse materials [1–3]. The whole printing process involves few steps for patterning of solution based materials, which make them unique and advantageous for reduced materials' wastage and manufacturing cost [2,4,5]. The early developments have resulted already in various proof of concept devices which lay an effective platform for future flexible and foldable electronic systems [6–8]. The various attractive electronic devices de- veloped on polymeric substrates so far also include micro-hotplates, which are central to a range of different sensing applications [8,9]. Micro-hotplates are self-heating devices, working on the principle of Joule's heating due to resistive metallic structures, conventionally de- veloped using silicon (Si) micromaching technologies [10,11]. Other approaches have also been proposed integrating micro-hotplates on porous silicon structures and glass substrates [12,13]. Micro-hotplates on polymeric foils have unique properties such as lower thermal con- ductivities, mechanical flexibility and lightweight distinguishing them from rigid silicon wafer based devices [8,14,15]. Printing is preferred on foils for its simple and cost-effective manufacturing compared to state of the art photolithography and etching techniques commonly practiced for Si based micro-hotplates. Inks containing silver nanoparticles are usually practiced for printing micro-hotplates on plastic substrates [8,14,16,17], however, they have serious issues of oxidation and non-stability due to electromigration under higher tem- peratures [18]. Printing of a stable metal such as gold (Au) has been considered to allow better stability at variant operating conditions. Limited work has been reported on printed Au micro-hotplates on polymeric substrates such as polyimide (PI). One such approach was based on an inkjet printed heater on the backside of a 50 μm thick substrate with an effective area larger than 2 mm 2 [19,20]. These de- vices have been reported to consume higher power i.e. 590 mW at 300 °C [19], which is much higher than the power consumption of miniaturized micro-hotplates developed on thin SiN (silicon nitride|) membranes using standard microfabrication technology [21,22]. Therefore in this research, we focus on reducing the overall size of the microheater as well as printing on membranes as thin as 5 μm to achieve low power consumption for printed hotplates. PI substrate with 50 μm of thickness was used in this study, which was thinned down to 5 μm using laser etching for improved thermal insulation. A high resolution digital printing technique i.e. Aerosol jet was employed to minimize the effective size of the micro-hotplate, in comparison to inkjet printed reported in the previously reported work [16,17]. Under ideal conditions, aerosol jet technique is capable of printing down to 10 μm wide patterns, making it of interest for high resolution patterning of metallic lines. Using this printing technique, we https://doi.org/10.1016/j.mee.2018.03.013 Received 10 March 2018; Accepted 14 March 2018 ⁎ Corresponding author. E-mail address: saleem.khan@epfl.ch (S. Khan). Microelectronic Engineering 194 (2018) 71–78 Available online 17 March 2018 0167-9317/ © 2018 Published by Elsevier B.V. T