Nano-structural characteristics of carbon nanotube–polymer composite films for high-amplitude optoacoustic generation

Baac, Hyoung Won; Ok, Jong G.; Lee, Taehwa; Guo, L. Jay

doi:10.1039/c5nr03769g

Cited by 60 publications

(56 citation statements)

References 31 publications

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“…This trend can be explained by the fact that the output PA amplitude ( P ) is primarily determined by the PA amplitude produced in the surrounding materials with high thermal expansion ( P s ), i.e.,

P = P_{normalm} + P_{normals} ≅ P_{normals}

. Here, P s can be represented by

P_{s} = A \cdot Γ \cdot (F / l) \cdot γ_{s}

, where A , Γ, F / l , and

γ_{normals}

are the light absorption, the Grüneisen parameter, the energy volume density, and the heat energy in the surrounding layers, respectively. Therefore, the normalized output PA amplitude ( P / A ) can be expressed by

P / A ≅ P_{normals} / A = Γ \cdot (F / l) \cdot γ_{normals}

.…”

Section: Resultsmentioning

confidence: 99%

“…By reducing the thickness of the Cr layer down to 10 nm, the thermal energy is effectively transferred into the surrounding PDMS layers (almost 70%). Thus, to make use of PDMS with high thermal expansion but with low heat capacity, it is very effective to use absorbers with much lower heat capacity for rapid heat transfer to the surroundings (e.g., low density nanometer‐sized carbon fillers satisfies this requirement).…”

Section: Resultsmentioning

confidence: 99%

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Highly Efficient Photoacoustic Conversion by Facilitated Heat Transfer in Ultrathin Metal Film Sandwiched by Polymer Layers

Lee

Guo

2016

Advanced Optical Materials

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of biomaterials (tissue damage threshold, 20 mJ cm −2 [6] ). Therefore, there is a strong need to find a system that can increase the PA conversion efficiency.PA conversion, particularly via the thermoelastic effect, depends on material properties such as thermal expansion coefficient (β) and light absorption coefficient (α) (i.e., Photoacoustic pressure amplitude, P = Γ(β)αF where the Grüneisen parameter, Γ is a function of β, and F is the laser fluence). [2] Efficient PA materials should have both high thermal expansion and good light absorption. Among many materials, metal films (typically, hundreds of nanometers thick) have been widely used due to easy fabrication and decent light absorption (e.g., >50% light absorption for Cr 100 nm at 532 nm wavelength). However, the PA conversion of metals is considered to be inefficient because of their low thermal expansion. Alternatively, researchers have developed composite materials with both high thermal expansion and good light absorption, [7][8][9][10][11] which consist of lightabsorbing fillers embedded in transparent mediums with high thermal expansion. Specifically, an early attempt to make such composites was to use carbon black mixed with polydimethylsiloxane (PDMS), which showed an order of magnitude high PA amplitude compared to a metal film. [7] Recently, besides carbon black, other carbon materials including CNTs, [8,9] rGO, [10] candle soot nanoparticles, [11] and nanofiber [12] have been utilized as light-absorbing fillers, showing improved PA conversion efficiency. In addition to the carbon-based broadband absorbers, a metal-based PDMS composite consisting of gold nanoparticles was developed, showing high PA conversion efficiency compared to aluminum thin film. [13] Beyond imaging and sensing applications, such highly efficient PA materials have allowed new applications, e.g., PA cavitation therapy capable of selectively removing biomaterials, cells or tissues. [14][15][16][17] Although the composite materials are proven to be promising, they have several disadvantages. For example, the composites require arduous preparation processes (e.g., high temperature CVD growth of CNT forest [8] ). Also, the carbon fillers are easily agglomerated while mixing with polymers, thereby requiring surface functionalization of the fillers. [9] Moreover, for solutionprocessed composites, it is difficult to control the thickness of the films, especially if the composites contain a high concentration of fillers and thus become highly viscous. [8,18] Even though main contribution to efficient PA conversion is believed to be Photoacoustic (PA) conversion of metal film absorbers is known to be inefficient because of their low thermal expansion and high optical reflection, as compared to polymeric materials containing light absorbing fillers. Here, highly efficient PA conversion is demonstrated in metal films. By using a metal film absorber sandwiched by transparent polymer layers, PA conversion is significantly enhanced, which is even comparable to in the highest reported in...

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P = P_{normalm} + P_{normals} ≅ P_{normals}

. Here, P s can be represented by

P_{s} = A \cdot Γ \cdot (F / l) \cdot γ_{s}

, where A , Γ, F / l , and

γ_{normals}

P / A ≅ P_{normals} / A = Γ \cdot (F / l) \cdot γ_{normals}

.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Highly Efficient Photoacoustic Conversion by Facilitated Heat Transfer in Ultrathin Metal Film Sandwiched by Polymer Layers

Lee

Guo

2016

Advanced Optical Materials

Self Cite

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“…The amplitude of ultrasound produced by CB-PDMS is slightly less than that by AuNPs-PDMS [43]. (ii) CNT nanocomposites are demonstrated as highly-efficient and high-frequency LGUS transmitters [30,[53][54][55]. The CNT nanocomposite shows five times enhancement compared with the above-mentioned 2D AuNPs nanocomposite with the same polymer PDMS [43] and a broad bandwidth up to 120 MHz.…”

Section: Carbon-based Absorbersmentioning

confidence: 80%

“…(iv) More recently, candle soot carbon NPs (CSNPs)-PDMS nanocomposites are explored [57]. Figure 2 shows SEM pictures of CNTs, CNFs and CSNPs used in References [55][56][57], respectively. The ratio of photoacoustic conversion efficiency for CSNPs-PDMS, CNFs-PDMS, CNTs-PDMS, and CB-PDMS is 13:4.9:4.1:1 [57].…”

Section: Carbon-based Absorbersmentioning

confidence: 99%

Review of Laser-Generated Ultrasound Transmitters and Their Applications to All-Optical Ultrasound Transducers and Imaging

Chen

2016

Applied Sciences

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Abstract:Medical ultrasound is an imaging technique that utilizes ultrasonic signals as information carriers, and has wide applications such as seeing internal body structures, finding a source of a disease, and examining pregnant women. The most commonly used ultrasonic transducer today is based on piezoelectricity. The piezoelectric transducer, however, may have a limited bandwidth and insufficient sensitivity for reduced element size. Laser-generated ultrasound (LGUS) technique is an effective way to resolve these issues. The LGUS approach based on photoacoustic effect is able to greatly enhance the bandwidth of ultrasound signals and has the potential for high-resolution imaging. High-amplitude LGUS could also be used for therapy to accomplish high precision surgery without an incision. Furthermore, LGUS in conjunction with optical detection of ultrasound allows all-optical ultrasound imaging (i.e., ultrasound is generated and received optically). The all-optical platform offers unique advantages in providing high-resolution information and in facilitating the construction of miniature probes for endoscopic ultrasound. In this article, a detailed review of the recent development of various LGUS transmitters is presented. In addition, a recent research interest in all-optical ultrasound imaging, as well as its applications, is also discussed.

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“…However, the customisable structure and composition of nanomaterials have motivated their status as perhaps the most 'engineerable' platforms for PAI, particularly for integrating photoacoustic imaging with MRI, OI and therapeutic strategies. Recent years have witnessed the successful application of approaches involving metal-based (nanoparticles, nanorods, nanoshells and nanocages) and carbon-based (carbon dots, nanotubes, nanopolymers and nanovesicles) nanomaterials for targeting cell-specific antigens or the microenvironment (pH, pO2 sensing), or for passive targeting (that is, by taking advantage of the enhanced permeability and retention effect) in PAI 94,[99][100][101][102][103][104][105][106] . Although PAI is limited by tissue-penetration depth of the requisite excitation light, its clinical outlook is terrific for the early detection and monitoring of superficial or near-surface lesions, as well as those accessible via endoscopy.…”

Section: Paimentioning

confidence: 99%

Multiplexed imaging for diagnosis and therapy

et al. 2017

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Complex molecular and metabolic phenotypes depict cancers as a constellation of different diseases with common themes. Precision imaging of such phenotypes requires flexible and tuneable modalities capable of identifying phenotypic fingerprints by using a restricted number of parameters whilst ensuring sensitivity to dynamic biological regulation. Common phenotypes can be detected by in vivo imaging technologies, and effectively define the emerging standards for disease classification and patient stratification in radiology. However, for the imaging data to accurately represent a complex fingerprint, the individual imaging parameters need to be measured and analysed in relation to their wider spatial and molecular context. In this respect, targeted palettes of molecular imaging probes facilitate the detection of heterogeneity in oncogene-driven alterations and their response to treatment, and lead to the expansion of rational-design elements for the combination of imaging experiments. In this Review, we evaluate criteria for conducting multiplexed imaging, and discuss its opportunities for improving patient diagnosis and the monitoring of therapy.

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Nano-structural characteristics of carbon nanotube–polymer composite films for high-amplitude optoacoustic generation

Cited by 60 publications

References 31 publications

Highly Efficient Photoacoustic Conversion by Facilitated Heat Transfer in Ultrathin Metal Film Sandwiched by Polymer Layers

Highly Efficient Photoacoustic Conversion by Facilitated Heat Transfer in Ultrathin Metal Film Sandwiched by Polymer Layers

Review of Laser-Generated Ultrasound Transmitters and Their Applications to All-Optical Ultrasound Transducers and Imaging

Multiplexed imaging for diagnosis and therapy

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