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There has been an increasing need of technologies to manufacturing chemical and biological sensors for various applications ranging from environmental monitoring to human health monitoring. Currently, manufacturing of most chemical and biological sensors relies on a variety of standard microfabrication techniques, such as physical vapor deposition and photolithography, and materials such as metals and semiconductors. Though functional, they are hampered by high cost materials, rigid substrates, and limited surface area. Paper based sensors offer an intriguing alternative that is low cost, mechanically flexible, has the inherent ability to filter and separate analytes, and offers a high surface area, permeable framework advantageous to liquid and vapor sensing. However, a major drawback is that standard microfabrication techniques cannot be used in paper sensor fabrication. To fabricate sensors on paper, low temperature additive techniques must be used, which will require new manufacturing processes and advanced functional materials. In this work, we focus on using aerosol jet printing as a highresolution additive process for the deposition of ink materials to be used in paper-based sensors. This technique can use a wide variety of materials with different viscosities, including materials with high porosity and particles inherent to paper. One area of our efforts involves creating interdigitated microelectrodes on paper in a one-step process using commercially available silver nanoparticle and carbon black based conductive inks. Another area involves use of specialized filter papers as substrates, such as multi-layered fibrous membrane paper consisting of a poly(acrylonitrile) nanofibrous layer and a nonwoven poly(ethylene terephthalate) layer. The poly(acrylonitrile) nanofibrous layer are dense and smooth enough to allow for high resolution aerosol jet printing. With additively fabricated electrodes on the paper, molecularly-functionalized metal nanoparticles are deposited by molecularly-mediated assembling, drop casting, and printing (sensing and electrode materials), allowing full functionalization of the paper, and producing sensor devices with high surface area. These sensors, depending on the electrode configuration, are used for detection of chemical and biological species in vapor phase, such as water vapor and volatile organic compounds, making them applicable to human performance monitoring. These paper based sensors are shown to display an enhancement in sensitivity, as compared to control devices fabricated on non-porous polyimide substrates. These results have demonstrated the feasibility of paper-based printed devices towards manufacturing of a fully wearable, highly-sensitive, and wireless human performance monitor coupled to flexible electronics with the capability to communicate wirelessly to a smartphone or other electronics for data logging and analysis.
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Electromechanical characterization and computational analysis of the corona-enabled electrostatic printed flexible strain sensors
Printed flexible electronics have received extensive attention due to their significant potential for advancing wearable technologies, such as for monitoring human physiological health and biomechanics. However, current manufacturing techniques (e.g., inkjet printing and screen printing) of these electronics are typically limited by high cost, lengthy fabrication times, and types of print materials. Thus, this study investigates a novel manufacturing technique, namely corona-enabled electrostatic printing (CEP), which leverages high voltage discharged in the air to attract feedstock material particles onto substrates. The CEP technique can potentially fabricate various functional materials in milliseconds, forming binder-free microstructures. This study focuses on optimizing the CEP technique to produce high-performance, flexible, piezoresistive strain sensors. Here, the strain sensors will be fabricated with carbon nanotubes (CNTs) using different discharge voltages. The effect of the discharge voltage (i.e., a critical fabrication parameter) on the sensing performance will be characterized via electromechanical testing. In addition, to better understand the sensing mechanism of the samples, finite element analysis will be performed to investigate the electromechanical response of the CEP-fabricated binder-free CNT networks. Here, computational material models will be established based on microstructures of the CNT networks, which will be acquired from experimental microscopic imaging. Overall, this study will fundamentally advance the CEP manufacturing process for flexible electronics.
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- Award ID(s):
- 2114223
- PAR ID:
- 10536553
- Editor(s):
- Wissa, Aimy; Gutierrez_Soto, Mariantonieta; Mailen, Russell W
- Publisher / Repository:
- SPIE
- Date Published:
- ISBN:
- 9781510672000
- Page Range / eLocation ID:
- 6
- Subject(s) / Keyword(s):
- advanced manufacturing carbon nanotubes flexible electronics microstructure strain sensing
- Format(s):
- Medium: X
- Location:
- Long Beach, United States
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1117/12.3010504
