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1. Dry Printing and Additive Nanomanufacturing of Flexible Hybrid Electronics and Sensors

   https://doi.org/10.1002/admi.202102569  

   Ahmadi, Zabihollah ; Lee, Seungjong ; Patel, Aarsh ; Unocic, Raymond R. ; Shamsaei, Nima ; Mahjouri‐Samani, Masoud ( February 2022 , Advanced Materials Interfaces)

   The growing demand for flexible and wearable hybrid electronics has triggered the need for advanced manufacturing techniques with versatile printing capabilities. Complex ink formulations, use of surfactants/contaminants, limited source materials, and the need for high‐temperature heat treatments for sintering are major issues facing the current inkjet and aerosol printing methods. Here, the nanomanufacturing of flexible hybrid electronics (FHE) by dry printing silver and indium tin oxide on flexible substrates using a novel laser‐based additive nanomanufacturing process is reported. The electrical resistance of the printed lines is tailored during the print process by tuning the geometry and structure of the printed samples. Different FHE designs are fabricated and tested to check the performance of the devices. Mechanical reliability tests including cycling, bending, and stretching confirm the expected performance of the printed samples under different strain levels. This transformative liquid‐free process allows the on‐demand formation and in situ laser crystallization of nanoparticles for printing pure materials for future flexible and wearable electronics and sensors.

    

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2. Additive nanomanufacturing of metallic nanostructures through a kick-and-place approach (Conference Presentation)

   https://doi.org/10.1117/12.2319898  

   Zhao, Chenglong ( September 2018 , SPIE Proceedings)

   We investigated a mechanism for quick release and transfer of gold nanoparticles (GNPs) from a soft substrate to another substrate under laser illumination. The heating of GNPs on a soft substrate with a continuous-wave laser causes a rapid thermal expansion of the substrate, which can be used to selectively release and place GNPs onto another surface. In-plane and out-of-plane nanostructures are successfully fabricated using this method. This rapid release-and-place process can be used for additive nonmanufacturing of metallic nanostructures under ambient conditions, which paves a way for affordable nanomanufacturing and enables a wide variety of applications in nanophotonics, ultrasensitive sensing, and nonlinear plasmonics. 

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3. Ink‐Based Additive Nanomanufacturing of Functional Materials for Human‐Integrated Smart Wearables

   https://doi.org/10.1002/aisy.202000117  

   Xu, Shujia ; Wu, Wenzhuo ( July 2020 , Advanced Intelligent Systems)

   The economical, agile, customizable manufacturing, and integration of multifunctional device modules into networked systems with mechanical compliance and robustness enable unprecedented human‐integrated smart wearables and usher in exciting opportunities in emerging technologies. The additive manufacturing (AM) processes have emerged as potential candidates for rapid prototyping printed devices with diversified functionalities, e.g., energy harvesting/storage, sensing, actuation, and computation. However, there are few review reports about the ink‐based additive nanomanufacturing of functional materials for human‐integrated smart wearables. To fill this gap, herein, the recent progress in ink‐based additive nanomanufacturing technologies, focusing on their capability and potential for producing wearable human‐integrated devices, is reviewed. The manufacturing process integration, functional materials, device implementation, and application performance issues in designing and implementing the ink‐based additively nanomanufactured wearable systems are thoroughly discussed. The recent printed devices focusing on the processing conditions and performance metrics are comprehensively reviewed. Finally, the vision and outlook for the challenges and opportunities associated with related topics are provided. The rapid progress achieved in related disciplines enables more capable smart human‐integrated wearable systems that can be fully printed with rapid, agile, reconfigurable, and smart AM platforms.

    

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4. In-situ tension investigation of additively manufactured silver lines on flexible substrates

   https://doi.org/10.1016/j.addlet.2023.100171  

   Lee, Seungjong ; Ahmadi, Zabihollah ; Paul, Mikyle ; Mahjouri-Samani, Masoud ; Shao, Shuai ; Shamsaei, Nima ( December 2023 , Additive Manufacturing Letters)

   The reliability of additively manufactured flexible electronics or so-called printed electronics is defined as mean time to failure under service conditions, which often involve mechanical loads. It is thus important to understand the mechanical behavior of the printed materials under such conditions to ensure their applicational reliability in, for example, sensors, biomedical devices, battery and storage, and flexible hybrid electronics. In this article, a testing protocol to examine the print quality of additively nanomanufactured electronics is presented. The print quality is assessed by both tensile and electrical resistivity responses during in-situ tension tests. A laser based additive nanomanufacturing method is used to print conductive silver lines on polyimide substrates, which is then tested in-situ under tension inside a scanning electron microscope (SEM). The surface morphology of the printed lines is continuously monitored via the SEM until failure. In addition, the real-time electrical resistance variations of the printed silver lines are measured in-situ with a multimeter during tensile tests conducted outside of the SEM. The protocol is shown to be effective in assessing print quality and aiding process tuning. Finally, it is revealed that samples appearing identical under the SEM can have significant different tendencies to delaminate. 

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5. Additive Nanomanufacturing of Multifunctional Materials and Patterned Structures: A Novel Laser‐Based Dry Printing Process

   https://doi.org/10.1002/admt.202001260  

   Ahmadi, Zabihollah ; Lee, Seungjong ; Unocic, Raymond R. ; Shamsaei, Nima ; Mahjouri‐Samani, Masoud ( March 2021 , Advanced Materials Technologies)

   Direct printing of functional materials, structures, and devices on various platforms such as flexible to rigid substrates is of interest for applications ranging from electronics to energy and sensing to biomedical devices. Current additive manufacturing (AM) and printing processes are either limited by the available sources of functional materials or require to be in the form of precisely designed inks. Here, a novel laser‐based additive nanomanufacturing (ANM) system capable of in situ and on‐demand generations of nanoparticles that can serve as nanoscale building blocks for real‐time sintering and dry printing a variety of multifunctional materials and patterns at atmospheric pressure and room temperature is reported. The ability to print different functional materials on various rigid and flexible platforms is shown. This nonequilibrium process involves pulsed laser ablation of targets and in situ formation of pure amorphous nanoparticles’ stream that are guided through a nozzle onto the surface of the substrate, where they are sintered/crystallized in real‐time. Further, the process–structure relationship of the printed materials from nanoscale to microscale is shown. This new ANM concept opens up an opportunity for printing advanced functional materials and devices on rigid and flexible substrates that can be employed both on the earth and in space.

    

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