Carbon‐Nanotube–PDMS Composite Coatings on Optical Fibers for All‐Optical Ultrasound Imaging

Abstract

Polymer-carbon nanotube composite coatings have properties that are desirable for a wide range of applications. However, fabrication of these coatings onto submillimeter structures with the efficient use of nanotubes has been challenging. Polydimethylsiloxane (PDMS)-carbon nanotube composite coatings are of particular interest for optical ultrasound transmission, which shows promise for biomedical imaging and therapeutic applications. In this study, methods for fabricating composite coatings comprising PDMS and multiwalled carbon nanotubes (MWCNTs) with submicrometer thickness are developed and used to coat the distal ends of optical fibers. These methods include creating a MWCNT organogel using two solvents, dip coating of this organogel, and subsequent overcoating with PDMS. These coated fibers are used as all-optical ultrasound transmitters that achieve high ultrasound pressures (up to 21.5 MPa peak-to-peak) and broad frequency bandwidths (up to 39.8 MHz). Their clinical potential is demonstrated with all-optical pulse-echo ultrasound imaging of an aorta. The fabrication methods in this paper allow for the creation of thin, uniform carbon nanotube composites on miniature or temperature-sensitive surfaces, to enable a wide range of advanced sensing capabilities.

Acoustical characterisation of carbon nanotube-loaded polydimethylsiloxane used for optical ultrasound generation

“…As the increased attenuation inherently limits the achievable bandwidth, the coating thickness could be reduced to broaden the generated bandwidth. Alternatively, two-part coatings comprising a thin layer of CNT-loaded composite covered with a second layer of pure PDMS (which have previously been shown to generate wider bandwidths [3]) could be used to reduce the propagation distance through the more attenuative CNT-PDMS composite layer.…”

“…CNT-loaded samples were prepared using the method described in [3]. Briefly, multi-walled CNTs were first functionalised to allow for uniform dispersion in xylene, and then mixed with PDMS.…”

“…Consequently, optical acoustic sources are ideally suited to broadband material characterisation [5] and detector calibration. In addition, optical ultrasound sources have been successfully applied to biomedical imaging [3], [6]- [8] and therapeutic settings [9], [10].…”

“…Recent research efforts have focussed on the use of polydimethylsiloxane (PDMS) as a host material due to its high thermal expansion coefficient and its ease of fabrication and handling [3]. A variety of optical absorbers have been used, ranging from metals [11], [12] to carbon-based materials [3], [13]- [16].…”

Ultrasonic Needle Tracking with a Fibre-Optic Ultrasound Transmitter for Guidance of Minimally Invasive Fetal Surgery

“…As previously described in Refs. [14,15], the coating comprised multi-walled carbon nanotubes as optical absorbers and polydimethylsiloxane (PDMS) as an elastomeric host. The coating was applied to the distal end of an optical fibre (core diameter: 200 μm) with dip coating.…”