Abstract:
Background: This work develops a device design strategy of freely coatable and paintable paste-like broadband photo-thermoelectric (PTE) sensors by hybrid coupling structures of carbon nanotube (CNT) film absorber-channels and inorganic pn-junction electrode. As the structures of various industrial products become increasingly complex with improved functionality, non-destructive inspection techniques are indispensable to obtain detailed internal structural and defect information. In particular, non-destructive image measurement using broadband longer-wavelength electromagnetic waves (infrared–millimeter-waves) photo-monitoring techniques enables both structural reconstruction and material identification based on the difference in permeability of these wavelength bands. In this context, carbon nanotube (CNT) films are suitable for omni-directional non-destructive imaging devices for three-dimensional multilayered objects owing to their excellent physical durability and high absorption characteristics for ultrabroad IR-MMW bands. While PTE conversion by photo-induces heating and the associated broadband longer-wavelength photo- monitoring techniques have garnered attention for testing applications [1], efforts are still insufficient for synergistically combining photo-absorbent heating channels and high Seebeck coefficient TE electrodes. In short, the conventional use of single materials for PTE sensors regulates their functionalities (e.g., limited response ranges due to a lack of giant Seebeck coefficients).
To this end, this work focused on integrating ultrabroadband photo-thermal CNT film channels (absorptance over 90 %) and bismuth composite (Bicom: effective Seebeck coefficients over 240 µV/K) TE conversion electrodes.
Methods: This section explains the fabrication method of the hybrid PTE sensor in this work. The sensor adopts a device structure divided into an absorption part and a power generation part. The absorption part employs CNT, while the power generation part uses a Bicom. First, the Bicom prepares in paste form, and fabricates the power generation part using in screen printing. Next, the CNT inks prints as the absorption part using a dispenser. The dispenser is a equipment for applying a fixed amount of liquid. The dispenser used in this study is mounted on a robot arm that moves with high precision along the XYZ axes. By following the above steps, the hybrid PTE sensor is complete. In this work, screen printing applies to the Bicom, and a dispenser applies to the CNT ink due to the differences in their viscosities.
Results and conclusions: Owing to the aforementioned synergetic effect, the presenting device exhibits a 13-times higher response than that of the typical pn-junction CNT film PTE sensor. In addition, it showed a noise sensitivity of 3 pWHz–1/2, which is more sensitive than bolometric sensors and gas-filled sensors. For the usability, this work further demonstrates all-solution-processable configurations (e.g., for screen coating [2]) by designing stably formable and mechanically robust Bicom pastes together with inherently liquid-form CNTs.
Based on these results, the submitter will report on the specific process of device fabrication and the imaging results obtained with the fabricated devices at the conference.
Biography:
Leo Takai is a master's student in the Department of Electrical, Electronics, and Communication Engineering. He obtained his bachelor's degree from Chuo University in Japan and is still enrolled in a postgraduate course at the same university. He has been working on the research and development of non-destructive inspection devices utilizing carbon nanotubes and is currently focusing on optimizing the device fabrication method with the aim of practical application. He is actively engaged in research, including the publication of relevant papers and conference presentations.
Copyright 2024 Mathews International LLC All Rights Reserved
