Stretchable and Robust Candle-Soot Nanoparticle-Polydimethylsiloxane Composite Films for Laser-Ultrasound Transmitters

Abstract

<jats:p>Considerable attention has been devoted to the development of nanomaterial-based photoacoustic transmitters for ultrasound therapy and diagnosis applications. Here, we fabricate and characterize candle-soot nanoparticles (CSNPs) and polydimethylsiloxane (PDMS) composite-based photoacoustic transmitters, based on a solution process, not just to achieve high-frequency and high-amplitude pressure outputs, but also to develop physically stretchable ultrasound transmitters. Owing to its non-porous and non-agglomerative characteristics, the composite exhibits unique photo-thermal and mechanical properties. The output pressure amplitudes from CSNPs–PDMS composites were 20–26 dB stronger than those of Cr film, used as a reference. The proposed transmitters also offered a center frequency of 2.44–13.34 MHz and 6-dB bandwidths of 5.80–13.62 MHz. Importantly, we characterize the mechanical robustness of CSNPs–PDMS quantitatively, by measuring laser-damage thresholds, to evaluate the upper limit of laser energy that can be ultimately used as an input, i.e., proportional to the maximum-available pressure output. The transmitters could endure an input laser fluence of 54.3–108.6 mJ·cm−2. This is 1.65–3.30 times higher than the Cr film, and is significantly higher than the values of other CSNPs–PDMS transmitters reported elsewhere (22–81 mJ·cm−2). Moreover, we characterized the strain-dependent photoacoustic output of a stretchable nanocomposite film, obtained by delaminating it from the glass substrate. The transmitter could be elongated elastically up to a longitudinal strain of 0.59. Under this condition, it maintained a center frequency of 6.72–9.44 MHz, and 6-dB bandwidth ranges from 12.05 to 14.02 MHz. We believe that the stretchable CSNPs–PDMS composites would be useful in developing patch-type ultrasound devices conformally adhered on skin for diagnostic and therapeutic applications.</jats:p>

Comparison of Fabrication Methods for Fiber‐Optic Ultrasound Transmitters Using Candle‐Soot Nanoparticles

“…The fiber-optic CSNP-PDMS composites produced in this study generated wider bandwidths (>29 MHz) than those measured from the planar CSNP-PDMS composites fabricated in Faraz et al (13.62 MHz). [46] Additionally, the AiO CSNP-PDMS composites described in this work were applied directly to fiber-optic distal ends, which thereby presents different challenges to depositing macroscale films, and requires separate www.advmatinterfaces.de deposition methods, such as dip coating. Further, a comparison with another method for fabricating fiber-optic CSNP-PDMS composites (DD method) has been performed and the AiO method has shown to provide composites with very similar ultrasound pressures and bandwidths.…”

“…The photodetector split the signal into low frequency (<50 kHz) and high‐frequency (>500 kHz) components. The low‐frequency component of the signal (<50 kHz) was digitized at 16 bits with a sampling rate of 1 MS s −1 (PCI‐6251, National Instruments, UK) and was used to record the transfer function of plano‐concave microresonator, whilst the high‐frequency component (>500 kHz) was encoded with the received ultrasound signal [ 46 ] and digitized at 14 bits with a sampling rate of 100 MS s −1 (PCI‐5142, National Instruments, UK).…”

“…[19,39,[42][43][44] Also, they can be applied onto both curved and planar macroscale substrates. [18,[44][45][46][47] For example, CSNP-PDMS composites were applied onto concave substrates such as lenses, for use in high intensity focused ultrasound, [18,19,45,48] a therapeutic modality with wide-ranging medical applications including tumor therapy, [49] drug delivery, [50,51] and tissue ablation. [52,53] Many studies that have focused on developing CSNP composites for OpUS generation have demonstrated promising results when these composites have been produced as free-standing membranes.…”

Wave-Mode Configurable Ultrasonic Non-Destructive Evaluation System Using Optoacoustic Prism

“…Although the above proposed systems have adopted OA-based configurations for NDE applications, they have a common drawback of fixed acoustic wave-mode generation: for example, one of longitudinal, shear and Rayleigh modes. Owing to the recent advancement in transmitter fabrication technology, nanocomposite-based OA transmitters with extraordinary OA conversion efficiency have been developed [29][30][31][32][33][34][35][36].…”

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

“…The design of these layers ranges from pure nanoparticle coatings to pure metal layers, [5,[12][13][14][15][16][17] the mixed combination of nanoparticles, and polymers. [6,11,18,19] For the purpose of high optical absorption gold nanostructures, [20][21][22] graphite, [6,23] carbon fibers, [24,25] carbon black, [18,26] and candle soot [4,[27][28][29] have been investigated. One kind of nanoparticles is clearly outstanding for these applications [19,30,31] due to its extreme high and broadband optical absorption: [32][33][34][35] carbon nanotubes.…”