No abstract

Transducers for laser generated focused ultrasound can achieve photoacoustic waves with several hundred bars positive pressure in water. Previous designs employed concave glass substrates decorated with catalytically grown carbon nanotubes. Here, we show that arbitrarily shaped surfaces made of polymers and printed with 3d printers allow the generation of waveforms with complex temporal and spatial shape. We first present three different polymer materials together with a simplified deposition technique. This is achieved by painting layers of carbon-nanotube powder and polydimethylsiloxane. Together with a clear resin (Formlabs Photopolymer Clear Resin), pressure amplitudes of 300 bar peak positive were obtained. With the flexibility of polymer substrates, complex waveforms can be generated. This is demonstrated with a stepped surface which launches two waves separated by 0.8 μs. Detailed pressure measurements are supported with shadowgraphy images and simulations of the wave.

Neodymium (Nd3+)‐sensitized nanoconstructs have gained increasing attention in recent decades due to their unique properties, especially optical properties. The design of various Nd3+‐sensitized nanosystems is expected to contribute to medical and health applications, due to their advantageous properties such as high penetration depth, excellent photostability, non‐photobleaching, low cytotoxicity, etc. However, the low conversion efficiency and potential long‐term toxicity of Nd3+‐sensitized nanoconstructs are huge obstacles to their clinical translations. This review article summarizes three energy transfer pathways of all kinds of Nd3+‐sensitized nanoconstructs focusing on the properties of Nd3+ ions and discusses their recent potential applications as near‐infrared (NIR) enabled photomedicine. This review article will contribute to the design and fabrication of novel Nd3+‐sensitized nanoconstructs for NIR‐enabled photomedicine, aiming for potentially safer and more efficient designs to get closer to clinical usage.

Leakage flow through the disk clearance of a magnetically suspended centrifugal blood pump is essential for a good washout. An analytical approach, based on the theory of lubrication, is used to predict the leakage volume flow rate, nondimensional radial velocity, nondimensional mean pressure distribution, and comparative shear stress distribution for different disk clearance geometry under varying rotational speeds. The results showed that nondimensional mean pressure distribution and nondimensional radial velocity distribution along the clearance are independent of rotational speed. The flow through the gap depends on a nondimensional parameter S that denotes the ratio of centrifugal forces to the head generating capability of the impeller. It was found that an impeller having a lower S has less possibility of flow reversals in the gap, and gap with maximum height at the outside radius also is more susceptible to flow reversals at the impeller surface. The comparative shear stress within the gap reveals that, in general, the scalar stress is below 500 N/m2.

No abstract