CuInS2 Quantum Dot and Polydimethylsiloxane Nanocomposites for All-Optical Ultrasound and Photoacoustic Imaging.

Semyon Bodian,Ivan P Parkin,Paul C Beard,Yu Man Mandy Fong,Adrien E Desjardins,Paul Collier,Ross J Gordon,Filip Ambroz,Thomas J Macdonald,Sacha Noimark,Kathryn A Welsby,Sunish J Mathews,Efthymios Maneas,Richard J Colchester,Edward Z Zhang,Martha Briceno De Gutierrez

doi:10.1002/admi.202100518

Abstract

Dual‐modality imaging employing complementary modalities, such as all‐optical ultrasound and photoacoustic imaging, is emerging as a well‐suited technique for guiding minimally invasive surgical procedures. Quantum dots are a promising material for use in these dual‐modality imaging devices as they can provide wavelength‐selective optical absorption. The first quantum dot nanocomposite engineered for co‐registered laser‐generated ultrasound and photoacoustic imaging is presented. The nanocomposites developed, comprising CuInS2 quantum dots and medical‐grade polydimethylsiloxane (CIS‐PDMS), are applied onto the distal ends of miniature optical fibers. The films exhibit wavelength‐selective optical properties, with high optical absorption (> 90%) at 532 nm for ultrasound generation, and low optical absorption (< 5%) at near‐infrared wavelengths greater than 700 nm. Under pulsed laser irradiation, the CIS‐PDMS films generate ultrasound with pressures exceeding 3.5 MPa, with a corresponding bandwidth of 18 MHz. An ultrasound transducer is fabricated by pairing the coated optical fiber with a Fabry–Pérot (FP) fiber optic sensor. The wavelength‐selective nature of the film is exploited to enable co‐registered all‐optical ultrasound and photoacoustic imaging of an ink‐filled tube phantom. This work demonstrates the potential for quantum dots as wavelength‐selective absorbers for all‐optical ultrasound generation.

Highlights

Optically absorbing elastomeric nanocomposites can be formed as freestanding materials, applied as thin films on macro[1] and microscopic targets[2] and patterned using surface modification techniques such as soft lithography.[3]
All CIS-PDMS coatings were domed in shape and an orange/ red color characteristic of the CIS Quantum dots (QDs) (Figure 1a,b)
SEM images of fiber tips coated with solely the CIS QD underlayer displayed distinctive “bird-feet” patterns which are thought to result from the fast evaporation of the residual toluene solvent from the CIS QD paste (Figure S1, Supporting Information)

Summary

Introduction

Optically absorbing elastomeric nanocomposites can be formed as freestanding materials, applied as thin films on macro[1] and microscopic targets[2] and patterned using surface modification techniques such as soft lithography.[3]. These elastomeric composites have shown great promise in biomedical imaging, in particular for optical ultrasound (OpUS) generation.[7,8,9,10,11] Here, the elastomeric composite film absorbs a pulsed or modulated light source generating ultrasound waves via the photoacoustic effect.[10,12,13] OpUS transmitters are advantageous since they can generate high ultrasound pressures and bandwidths from miniature devices without compromising their generation efficiencies; they are immune to electromagnetic interference and have the potential for low-cost production.[8,14,15]

Methods

Results

Discussion

Conclusion