Pristine carbon nanotubes are efficient absorbers at radio frequencies

Abstract

Radio frequency ablation and microwave hyperthermia are powerful tools for destroying dysfunctional biological tissues, but wireless application of these techniques is hindered by the inability to focus the electromagnetic energy to small targets. The use of locally injected radio frequency- or microwave-absorbing nanomaterials can help to overcome this challenge by confining heat production to the injected region. Previous theoretical work suggests that high-aspect-ratio conducting nanomaterials, such as carbon nanotubes, offer powerful radio frequency and microwave absorption. While carbon nanotubes have been previously studied for radio frequency and microwave hyperthermia enhancement, these studies have employed sonication for sample preparation, reducing the volume fraction and average length within the carbon nanotube suspensions. In this manuscript, we use a sonication-free preparation technique to preserve both the length of carbon nanotubes and the high volume fraction of their bundled state. We measure the heating of these samples at 2 GHz compared to the heating of a biological tissue reference using infrared thermography. We report an increase in heating by 4.5 fold compared to the tissue reference, with localized heating clearly observable within a three-dimensional biological tissue phantom. Numerical simulations further aid in producing a temperature map within the phantom and demonstrating localized heating. Due to their significant differential heating ratio, we believe that sonication-free carbon nanotube samples may bring unforeseen opportunities to the fields of radio frequency ablation and microwave hyperthermia.

Nanotransducer-Enabled Deep-Brain Neuromodulation with NIR-II Light

“…Such limitation comes from the intrinsic light–tissue interaction, with one potential direction to address this challenge by looking at other frequency ranges in the electromagnetic spectrum for much deeper penetration. For example, radiofrequency waves such as WiFi can penetrate tens of centimeters in biological tissues, and we thus envision that the development of biomaterials which can strongly interact with RF signals may eventually enable non-invasive neuromodulation throughout the entire human brain. − …”