Fiber‐Optic Photoacoustic Generator Realized by Inkjet‐Printing of CNT‐PDMS Composites on Fiber End Faces

In recent years, photoacoustic generators based on multiwalled carbon nanotubes (MWCNT) and polydimethylsiloxane (PDMS) are manufactured in a variety of ways, which influences the properties of the generators with respect to frequency bandwidth, sound wave pressure, robustness, and reproducibility. Due to the high optical absorption of MWCNTs and the high thermal expansion coefficient of PDMS, this combination is ideally suited for use as a photoacoustic generator. This study presents a novel method to produce photoacoustic generators based on long‐term stable MWCNT and PDMS inks with a high reproducibility by means of inkjet‐printing. The MWCNT‐PDMS layers (thicknesses of 2–4 µm), printed directly onto the distal end face of a multimode glass fiber, show a good homogeneity and low optical transmission (19–21%). After the preparation of the fiber pieces, the inkjet printer performs all steps automatically in a time period of 30–60 s per layer. The generated ultrasonic pressure (0.39–0.54 MPa) and frequency bandwidth (1.5–12.7 MHz) can be measured at a distance of ≈4 mm with a laser fluency of 12.7 mJ cm−2. These highly reproducible printed photoacoustic generators can be well used for nondestructive material testing and medical applications. This paper deals with the first fully inkjet‐printed photoacoustic generator based on carbon nanotube (CNT) and polydimethylsiloxane (PDMS) inks. The investigation results and applications are focused on the conception and production of long‐term stable CNT‐PDMS inks and CNT‐curing agent inks for the printing process, which are then used for the production of thin films for use as photoacoustic generators at high ultrasonic frequency.