Development of a New Generation of Ammonia Sensors on Printed Polymeric Hotplates

Abstract

Conducting polyaniline-based chemiresistors on printed polymeric micro-hotplates were developed, showing sensitive and selective detection of ammonia vapor in air. The devices consist of a fully inkjet-printed silver heater and interdigitated electrodes on a polyethylene naphthalate substrate, separated by a thin dielectric film. The integrated heater allowed operation at elevated temperatures, enhancing the ammonia sensing performance. The printed sensor designs were optimized over two different generations, to improve the thermal performance through careful design of the shape and dimension of the heater element. A vapor-phase deposition polymerization technique was adapted to produce polyaniline sensing layers doped with poly(4-styrenesulfonic acid). The resulting sensor had better thermal stability and sensing performance when compared with conventional polyaniline-based sensors, and this was attributed to the polymeric dopant used in this study. Improved long-term stability of the sensors was achieved by electrodeposition of gold on the silver electrodes. Response to sub-parts-per-million concentrations of ammonia even under humid conditions was observed.

Fully inkjet printed SnO2 gas sensor on plastic substrate

“…Among the different printing techniques, ink-jet printing is a contactless technique able to deliver digitally precise quantities of materials to form well-defined patterns. This technique is used for the preparation of different functional films [1,[8][9][10][11].…”

Initiated Chemical Vapor Deposition: A Versatile Tool for Various Device Applications

“…CVD techniques can be categorized into two groups based on the deposition mechanisms involved: 1) chain growth polymerization (e.g., plasma enhanced CVD(PECVD) and initiated CVD (iCVD)); and 2) step growth polymerization (e.g., vapor deposition polymerization (VDP), Parylene, and oxidative CVD (oCVD)). iCVD presents an advantage over other CVD techniques (plasma enhanced CVD (PECVD), pulsed‐plasma CVD(PPCVD), and parylene CVD) in its higher retention of chemical functional groups, as iCVD film is deposited under relatively mild process conditions .…”

Aerosol Jet Printing of Miniaturized, Low Power Flexible Micro-Hotplates

“…The direct manufacturing of functional layers in a single-step make them unique and advantageous for reduced materials wastage and manufacturing cost. Different devices on flexible substrates have been developed so far including micro-hotplates, which are central to a range of different sensing applications [2,3]. Micro-hotplates are self-heating devices, working on the principle of Joule's heating due to resistive structures.…”

“…Printing is preferred on foils for its simple and cost-effective manufacturing compared to state of the art photolithography and etching techniques. Silver based inks are usually practiced for printing microhotplates on flexible substrates [2,6], however, they have serious issues of oxidation and non-stability under high temperatures. Printing of a stable metal such as gold (Au) has been considered to allow better stability at variant conditions.…”

“…Limited work has been reported on printed gold micro-hotplates on flexible 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 [2,6]. This increases significantly the power consμmption desired to be as minimμm as possible for applications in miniaturized portable devices [6].…”