Session: 04-03 Emerging Technologies: New Applications of AM

Paper Number: 92250

92250 - Encapsulating and Inkjet-Printing Electronics on Flexible Substrates for Harsh Environment 

Flexible electronics devices have recently gained popularity in broad application areas including space exploration, downhole oil and gas industries, biomedical industries, automotive industries, marine applications, etc. This causes the material to expose to harsh environmental conditions, like extreme temperature, changing pressure, severe radiation, hazardous chemicals, humidity, salinity, or a blend of these conditions. Thus, for the device to perform its intended function, it is required to have some degree of protection against these conditions. The conductive material is the core of the device for desirable function. To sustain a harsh environment, we can use some alternatives, such as a specialized conductive material that has the inherent property to resist the harsh environment or specialized packaging materials that can encapsulate the traditionally used conductive material, to achieve the desired objective. Between the two alternatives, encapsulation is economically feasible and effective.

In our case, we aim to develop an intrinsically safe and hermetically packaged/encapsulated flexible sensor submerged in hydrocarbon fluid for pump health monitoring. Thus, we propose to encapsulate a flexible electronics sensor using a material that can withstand harsh crude oil conditions. Meanwhile, such a material can be a substrate of the flexible electronic sensor and a novel fabrication process needs to be designed for this material-based sensor. Generally, flexible electronics can be fabricated using various contact and non-contact printing techniques. Among them, inkjet printing is popular because of its ability to print directly on a flexible/stretchable substrate like Rubber, PDMS (Polydimethylsiloxane), Polyethylene terephthalate (PET), etc. However, inkjet printing on such a substrate is challenging due to surface energy mismatch between the ink and the substrate which might lead to non-uniform ink deposition or microcrack propagation in the conductive path of the circuit.

In this paper, we design an optimized printing process and encapsulation over the printed circuit to make it robust and ensure the reliable working of the device in any given environmental conditions. We propose an optimized process of multilayer inkjet printing of silver ink on flexible substrates like Polydimethylsiloxane (PDMS) and Rubber which will overcome the challenge of surface energy mismatch consequently overcoming non-uniform ink deposition and further adding a layer of non-conductive encapsulation on the circuit. Encapsulation material provides protection against harsh environments, flexibility to the circuit, uniform stress distribution which restricts the initiation and propagation of microcracks in the circuit resulting in better electrical and mechanical stability. We validated this method by measuring the actual and theoretical resistance values of the printed patterns on the flexible substrates. Further, we encapsulated our circuit by adding an encapsulation layer and checked the performance of the circuits at elevated temperatures in hydraulic oil. Our printing process yields good printing results wherein we found the actual and theoretical values of resistance on each substrate were comparable and added encapsulation layer was successful to retain the electro-mechanical performance of the circuit. We extended our methodology to multiple flexible substrates, unlike other literature which focuses their process only on single substrates for printing, we formulated a single process that can be used for multiple flexible substrates.

Presenting Author: Xian Du University of Massachusetts Amherst

Presenting Author Biography: Dr. Xian Du is an Assistant Professor with the Mechanical and Industrial Engineering Department and Institute for Applied Life Sciences at the University of Massachusetts, Amherst, MA, USA. Before 2018, he was a research scientist at the Laboratory for Manufacturing Productivity at the Massachusetts Institute of Technology. His current research topic is the roll-to-roll flexible electronics printing technologies for wearable devices, and the innovation of real-time, high-resolution, and large-volume intelligent sensing and pattern recognition technologies for manufacturing process control and medical devices. His research interests include flexible electronics manufacturing, robotics, intelligent sensing, metrology, and physics-integrated machine intelligence. Dr. Du was the recipient of the NSF CAREER award in 2020 and is also a member of the IEEE, ASME, and OSA.

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