Spatially accurate & fast printing of testing sensors

    Led by Assistant Professor Kou Li, a research group in Chuo University, Japan, has developed an all-printable device fabrication strategy to resolve the existing technical limitations of multi-functional image sensor sheets for non-destructive inspections, with a recent paper publication in npj Flexible Electronics.

   While photo-thermoelectric (PTE) sensors and their ultrabroadband monitoring facilitate non-destructive testing, their conventional fabrication is insufficient for high-yield integration. Specifically, PTE devices faced challenges in their crucial spatial-misalignment for separate fabrication processes per constituent. Herein, this work demonstrates mechanically alignable and all-dispenser-printable integration of carbon nanotube (CNT) functional PTE sensor devices by designing them with solution-processable ink-materials. This technique first accurately prints CNT channels, essential in PTE conversion, using higher-concentration inks, and integrates remaining constituents (dopants and conductive pastes) into single device structures at high-yield. This work further demonstrates that employing higher-concentration CNT inks, suitable for mechanical channel printing, also designs sensitive PTE sensors. These sensors serve stably as integrated devices on diverse functional substrates, facilitating ubiquitous non-destructive monitoring depending on features. Therefore, this work designs such CNT PTE integrated devices and the associated functional inspection appropriately for structures, sizes, and external environments (e.g., temperature and humidity) of monitoring targets.

   While photo-thermoelectric (PTE) sensor sheets and their inherent omni-directional ultrabroadband monitoring facilitate functional material and structural identifying non-destructive testing, their conventional fabrication is insufficient for high-yield integration. Specifically, PTE devices faced challenges to large-scale integration for their crucial spatial-misalignment caused by separate fabrication processes of constituent parts.

   To this end, this manuscript made the following significant contributions.

1. Preparing respective constituent materials of the functional PTE sensor sheets in liquid ink forms to be effectively adopted for all-solution-processable consecutive fabrication processes within a single platform as follows: carbon nanotube (CNT) photo-absorber channels, wiring electrodes, and carrier dopants.

2. Developing high-yield formation and integration processes among each constituent part of the above CNT film PTE sensor sheet without conventionally bottlenecking manual spatial alignment steps by consistently handling all device inks with a single air-jet mechanical dispense printer.

3. Demonstrating that the use of highly-concentrated CNT inks, which are essential in high-yield printing, collectively satisfies ultrabroad photo-detection operations over typical wideband detectors with comparable sensitivities to existing narrowband devices, as the core material role in the PTE sensor sheet.

4. Enriching the usability of the CNT film PTE sensor sheets as ubiquitous inspection tools in diverse module configurations (e.g., high-resolution imagers, wearable gloves, and transparent patch-scanners) via universal and high-yield all-dispenser-printable device formations regardless of substrates.

   The paper was published online in the international scientific journal, npj Flexible Electronics (May 8, 2025).

<Researcher>

<Authors>
Minami Yamamoto^†,1, Daiki Sakai^†,1, Yuto Matsuzaki^†,1, Leo Takai¹, Yukito Kon¹, Yuto Aoshima¹, Noa Izumi¹, Naoko Hagiwara¹, Hayato Hamashima¹, Daiki Shikichi¹, Junyu Jin¹, Qi Zhang¹, Kohei Murakami¹, Yuya Kinoshita¹, Satsuki Yasui¹, Norika Takahashi¹, Hajime Nishiyama^2,3, Yukio Kawano*^,1,4,5, and Kou Li*^,1

^†Co-first author
^*Corresponding author

<Affiliation>
¹Department of Electrical, Electronic, and Communication Engineering, Faculty of Science and Engineering, Chuo University
²Laboratory for Future Interdisciplinary Research of Science and Technology, Tokyo Institute of Technology
³Department of Electrical and Electronic Engineering, School of Engineering, Tokyo Institute of Technology
⁴National Institute of Informatics
⁵Kanagawa Industrial Institute of Science and Technology