Exosomes, which are membranous nanovesicles, are actively released by cells and have been attributed to roles in cell-cell communication, cancer metastasis, and early disease diagnostics. The small size (30–100 nm) along with low refractive index contrast of exosomes makes direct characterization and phenotypical classification very difficult. In this work we present a method based on Single Particle Interferometric Reflectance Imaging Sensor (SP-IRIS) that allows multiplexed phenotyping and digital counting of various populations of individual exosomes (>50 nm) captured on a microarray-based solid phase chip. We demonstrate these characterization concepts using purified exosomes from a HEK 293 cell culture. As a demonstration of clinical utility, we characterize exosomes directly from human cerebrospinal fluid (hCSF). Our interferometric imaging method could capture, from a very small hCSF volume (20 uL), nanoparticles that have a size compatible with exosomes, using antibodies directed against tetraspanins. With this unprecedented capability, we foresee revolutionary implications in the clinical field with improvements in diagnosis and stratification of patients affected by different disorders.

The authors present a technique that allows to modify the local characteristics of two-dimensional photonic crystals by controlled microinfiltration of liquids. They demonstrate experimentally that by addressing and infiltrating each pore with a simple liquid, e.g., water, it is possible to write pixel by pixel optical devices of any geometry and shape. Calculations confirm that the obtained structures indeed constitute the desired resonators and waveguide structures.

High formation yield and a meaningful cooled fraction of positronium below room temperature were obtained by implanting positrons in a silicon target in which well-controlled oxidized nanochannels (5\char21{}8~nm in diameter) perpendicular to the surface were produced. We show that by implanting positrons at 7~keV in the target held at 150~K, about 27% of positrons form positronium that escapes into the vacuum. Around 9% of the escaped positronium is cooled by collision with the walls of nanochannels and is emitted with a Maxwellian beam at 150~K. Because positronium quantum confinement limits the minimum achievable positronium energy, the tuning of the nanochannel's size is crucial for obtaining positronium gases in vacuum at very low temperature.

A positron-positronium converter composed of regular nanochannels with size in the 5\char21{}100 nm range and length about 2$\hskip0.3em${}$\mu${}m has been produced in silicon by electrochemical etching. After controlled oxidation of the inner surface of the channels, a positronium yield up to 45% of the positrons implanted at 1 keV energy was observed. At 1 keV positron implantation energy about 42% of positronium is estimated to be emitted into the vacuum. At 10 keV positron implantation energy, corresponding to a depth of $\sim${}800$\hskip0.3em${}nm, the positronium fraction emitted into the vacuum is still 10% in a sample with channels of 4\char21{}7 nm and up to 23\char21{}25\,% in samples with larger channels. The positronium diffusion length and the fast positronium fraction emitted into the vacuum have been investigated as a function of the channel size tuned in the 5\char21{}100 nm range. The dependence of the positronium cooling from the size of the nanochannel is discussed and an evaluation of the expected fraction of thermalized orthopositronium in vacuum is given.