Broadband graphene-based photoacoustic microscopy with high sensitivity

Abstract

Photoacoustic microscopy (PAM) enables the measurement of properties associated with optical absorption within tissues and complements sophisticated technologies employing optical microscopy. An inadequate frequency response as determined by a piezoelectric ultrasonic transducer results, however, in poor depth resolution and inaccurate measurements of the coefficients of optical absorption. We developed a PAM system configured as an attenuated total reflectance sensor with a ten-layer graphene film sandwiched between a prism and water (the coupling medium) for photoacoustic (PA) wave detection. Transients of the PA pressure cause perturbations in the refractive index of the water thereby changing the polarization-dependent absorption of the graphene film. The signal in PA detection involves recording the difference in the temporal-varying reflectance intensity between the two orthogonally polarized probe beams. The graphene-based sensor has an estimated noise-equivalent-pressure sensitivity of ∼550 Pa over an approximately linear pressure response from 11.0 kPa to 55.0 kPa. Moreover, it enables a much broader PA bandwidth detection of up to ∼150 MHz, primarily dominated by a highly localized evanescent field. From the strong optical absorption of inherent hemoglobin, in vivo label-free PAM imaging provided a three-dimensional viewing of the microvasculature of a mouse ear. These results suggest great potential for graphene-based PAM in biomedical investigations, such as microcirculation studies.

Photoacoustic Imaging: Contrast Agents and Their Biomedical Applications

“…Two main categories of carbon‐based nanomaterials, namely, carbon nanotubes (CNTs) and graphene‐based nanomaterials, have been extensively investigated as contrast agents. Both categories have a distinct absorption in the NIR window.…”

“…Graphene‐based nanomaterials are another commonly used class of carbon‐based nanomaterial for PA imaging, extensively studied in the biomedical field because of their unique chemical and physical properties . Compared with CNTs, graphene‐based nanomaterials, especially reduced graphene oxide (rGO), possess a larger surface area and better dispersibility in most biological conditions.…”

Dual-Wavelength Continuous Wave Photoacoustic Doppler Flow Measurement

“…This study paves the way for further establishment of the multi-wavelength experiment system to get more complete absorption spectral information. Applying this spectroscopic technique in the blood flow measurement to fulfill the goal of accurately measuring the flow speed and at the same time, differentiating the oxygenation of the blood cells [19] can be anticipated by incorporating the tight focusing of the laser excitation and the high sensitive ultrasound detection [20].…”

Flexible fiber-laser ultrasound sensor for multiscale photoacoustic imaging

“…Based on their configurations, optical ultrasound sensors can be classified into free-space sensors and fiber/waveguide integrated sensors. Free-space sensors rely on the detection of ultrasonically-induced beam deflection 7 , surface displacement 8 , local reflective index modulation 9 , laser speckle correlation change 10 , or intensity change associated with surface plasmon resonance 11 , Fresnel reflections 12 or 2D materials 13 . These sensors offer noninvasive ultrasound detection and potential of integration with other interferometry-based sensing and imaging modalities, such as optical coherence tomography.…”