Photoacoustic (PA) imaging is a biomedical imaging method that can provide both structural and functional information of living tissues beyond the optical diffusion limit by combining the concepts of conventional optical and ultrasound imaging methods. Although endogenous chromophores can be utilized to acquire PA images of biological tissues, exogenous contrast agents that absorb near-infrared (NIR) lights have been extensively explored to improve the contrast and penetration depth of PA images. Here, we demonstrate Bi2Se3 nanoplates, that strongly absorbs NIR lights, as a contrast agent for PA imaging. In particularly, the Bi2Se3 nanoplates produce relatively strong PA signals with an optical wavelength of 1064 nm, which has several advantages for deep tissue imaging including: (1) relatively low absorption by other intrinsic chromophores, (2) cost-effective light source using Nd:YAG laser, and (3) higher available energy than other NIR lights according to American National Standards Institute (ANSI) safety limit. We have investigated deep tissue imaging capability of the Bi2Se3 nanoplates by acquiring in vitro PA images of microtubes under chicken breast tissues. We have also acquired in vivo PA images of bladders, gastrointestinal tracts, and sentinel lymph nodes in mice after injection of the Bi2Se3 nanoplates to verify their applicability to a variety of biomedical research. The results show the promising potential of the Bi2Se3 nanoplates as a PA contrast agent for deep tissue imaging with an optical wavelength of 1064 nm.
The fabrication of stretchable devices has been explored via two approaches: wavy design of non-stretchable materials or elastomeric electronic materials. The first approach has been widely used, specifically led by Rogers group. The second approach requests stretchability of all the device components, hence there have been no reports on the fabrication of semiconducting polymer-based stretchable transistors due to the lack of stretchable active layer and dielectric. This presentation deals with the fabrication of an array of highly stretchable polymer transistors made entirely of stretchable components. The transistors were constructed of stretchable Au nanosheet electrodes, polyelectrolyte gel for the gate dielectric, metal nanowires for the circuit, and nanofibril-based stretchable channel materials. This talk will present the issues of the components regarding with the stretchability and mechanical performance.