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Researchers Maruša Mur, Aljaž Kavčič, Uroš Jagodič, Rok Podlipec and Matjaž Humar from Condensed Matter Physics Department of the Jožef Stefan Institute have shown that 3D printing can be performed inside a living human cell. First, they injected droplets of a bio-compatible photo-curable material into cells. Then, using a highly focused laser beam, they selectively illuminated the printing material and polymerized it. By moving the laser beam in three dimensions, it is possible to “draw” complex structures of any shape with sub-micrometer resolution. Using this method, the team printed various structures, from geometric patterns to microlasers and even small elephants, all inside living human cells. The cells containing such structures can migrate and undergo cell division where the structure is passed into one of the daughter cells. By transforming living cells into miniature environments for 3D printing, this work pushes the boundaries of what is possible at the intersection of biology, physics, and engineering, offering a powerful new tool for exploring the workings of life from the inside out. The results were published in a paper in Advanced Materials, that was selected as an Editor’s Choice Paper.
 

The article was published in the journal Advanced Materials. M. Mur, A. Kavčič, U.… Read the rest “Article in Advanced Materials”

Colleagues from the department, Rok Podlipec, Ana Krišelj, and Matjaž Humar, in collaboration with the Department of Biochemistry, Molecular and Structural Biology and colleagues from the Helmholtz Center in Munich, have published an article in ACS Sensors on an exceptionally precise method for studying rapid dynamic processes at the level of individual adipocytes. In the study, they employed laser‑excited so‑called “whispering gallery mode” (WGM) optical resonances in lipid droplets of live primary adipocytes, achieving nanometer‑scale accuracy in measuring droplet size, which significantly surpasses the resolution of conventional microscopy. By monitoring their dynamics, they explored complex responses to pharmacological agents, variability among individual cells—undetectable with standard bulk assays—and early changes in cell viability, faster than conventional tests. The presented method paves the way for investigations of metabolism and obesity‑related diseases at the level of single adipocytes and tissues.

More information can be found here: https://pubs.acs.org/doi/10.1021/acssensors.5c03272

Entangled photons represent one of the key building blocks of modern quantum technologies. In our study Electrically and Geometrically Tunable Photon Pair Entanglement from Ferroelectric Nematic Liquid Crystal, published in Advanced Science, we demonstrated that quantumly entangled photon pairs can be generated in ferroelectric nematic liquid crystals (FNLCs), while simultaneously enabling continuous tuning of their degree of entanglement.

We showed that the thickness of the liquid crystal sample, in combination with the molecular twist, has a significant impact on the quantum state of the photons generated via spontaneous parametric down-conversion. By appropriately varying these two parameters, it is possible to transition from separable to fully entangled states (within the limits of experimental uncertainty). Furthermore, we demonstrated that the degree of entanglement can be dynamically controlled in real time using an external electric field, which influences the molecular orientation within the sample.

The ability to achieve fast and straightforward electrical control over molecular orientation—and consequently over the quantum state—constitutes a key advantage of liquid crystals compared to conventional solid-state nonlinear crystals. These results point toward the development of so-called “quantum displays,” in which each pixel would function as an independent, electronically controlled quantum light source.

S. Klopčič, A. Kavčič, N. Sebastián, and M.… Read the rest “Electrically and Geometrically Tunable Photon Pair Entanglement from Ferroelectric Nematic Liquid Crystal”

The transmission of infectious diseases via aerosols in the indoor air remains a major public health hazard. Infected people expel respiratory droplets through breathing, coughing and sneezing, which can remain airborne for hours and contribute to the spread of infections.

Researchers Matjaž Malok, Darko Kavšek and Prof. Maja Remškar from the Department of Condensed Matter Physics at The Jožef Stefan Institute have developed the first sensor based on an innovative method for detecting individual respiratory droplets in the air. The detection is selective without the influence of other air pollutants, unlike existing air quality meters that do not separate respiratory droplets from solid particles. The selectivity of the detection is based on the difference in dielectric constant between water and solid particles.

In addition to respiratory droplets, the sensor device is suitable for measuring particles with a high dielectric constant, such as TiO2, droplets of cooling lubricants in the metal industry and pollen in outdoor air. The use of these devices enables data-driven ventilation, energy savings, and highlights the need for infection prevention measures in hospitals, schools, gyms, and other public spaces.

The article is published in the journal ACS Sensors, https://doi.org/10.1021/acssensors.5c02057

Spatial encoding in MRI is usually performed using gradient coils that produce a linearly increasing magnetic field Bz in a desired spatial direction such that its gradient is constant. However, it has been shown that spatial encoding in MRI can also be performed with coils that produce nonlinear magnetic fields. In this study, the performance of different types of nonlinear encoding coils, which have a simple design based on the use of a straight wire segment as a building block and a source of a highly nonlinear magnetic field, was experimentally tested in 2D and by simulation in 3D on coils with a nonsymmetric and a symmetric arrangement of these wire segments.  All images were reconstructed using our new reconstruction method, in which the signals spatially encoded by nonlinear coils are first transformed from the time- to the frequency-domain, yielding a distorted image (spectrum), which is then geometrically and intensity corrected. The results of the study may help advance the design of “gradient” coils towards freer geometries, higher magnetic field gradients or lower inductance and thus faster imaging.

TUŠAR, Kaja, SERŠA, Igor. Magnetic resonance imaging using a straight wire magnetic field for spatial signal encoding : imaging verification with 2D experiments and 3D modeling.… Read the rest “Magnetic resonance imaging using a straight wire magnetic field for spatial signal encoding : imaging verification with 2D experiments and 3D modeling”