Theoretical Development of Polymer-Based Integrated Lossy-Mode Resonance Sensor for Photonic Integrated Circuits

This research was funded by the European Regional Development Fund project “Development of a Novel Microfluidic Device for Label-Free Quantification of Prostate Cancer-Derived Extracellular Vesicles and Analysis of their RNA Content” (PROCEX) (1.1.1.1/20/A/045) and the European Union’s Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.A promising phenomenon such as lossy-mode resonance (LMR) is of great interest in sensor applications. Until now, this phenomenon has been shown only in fibers or planar waveguides; however, given the rapid development of such an important technological area as photonic integrated circuits (PICs), it is important to transfer LMR technology specifically to PICs. In this article, we propose the theoretical development of an integrated polymer-based LMR sensor that will also contribute to the development of hybrid organic–inorganic PICs. This work theoretically shows that LMR can be achieved using polymer SU-8 waveguides on a glass substrate, on top of which TiO2 is deposited. In addition, the paper shows that multiple resonances can be achieved in the developed integrated sensor. The highest sensor sensitivity (about 1400 nm/RIU) was achieved with 40 nm of TiO2. The effect of the waveguide and coating geometries, as well as the polarizations of propagating modes, is studied in this paper. © 2022 by the authors.ERDF 1.1.1.1/20/A/045; institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Pro gramme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2.

DEVELOPMENT OF LIQUID CRYSTAL LAYER THICKNESS AND REFRACTIVE INDEX MEASUREMENT METHODS FOR SCATTERING TYPE LIQUID CRYSTAL DISPLAYS

The research has been supported by ERDF No.1.1.1.1/19/A/120 “Improvement of Electro-Optical Characteristics of Liquid Crystal Shutters”.We report the measuring method of scattering type display liquid crystal layer thickness based on capacitance values suitable for inline production process control. The method is selected for its effectiveness and simplicity over spectroscopic methods as conventional methods for scattering type displays are not applicable. During the method approbation process, a novel diffuser liquid crystal mixture refractive index was determined based on liquid crystal layer thickness measurement data. © 2022 Sciendo. All rights reserved. --//-- This is an open access article Ozols A., Mozolevskis G., Zalubovskis R., Rutkis M. DEVELOPMENT OF LIQUID CRYSTAL LAYER THICKNESS AND REFRACTIVE INDEX MEASUREMENT METHODS FOR SCATTERING TYPE LIQUID CRYSTAL DISPLAYS (2022) Latvian Journal of Physics and Technical Sciences, 59 (4), pp. 25 - 35, DOI: 10.2478/lpts-2022-0031 published under the CC BY-NC-ND 4.0 licence.ERDF No.1.1.1.1/19/A/120; Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2.

Pulsed Electric Fields Alter Expression of NF-κB Promoter-Controlled Gene

The possibility to artificially adjust and fine‐tune gene expression is one of the key mile-stones in bioengineering, synthetic biology, and advanced medicine. Since the effects of proteins or other transgene products depend on the dosage, controlled gene expression is required for any ap-plications, where even slight fluctuations of the transgene product impact its function or other critical cell parameters. In this context, physical techniques demonstrate optimistic perspectives, and pulsed electric field technology is a potential candidate for a noninvasive, biophysical gene regulator, exploiting an easily adjustable pulse generating device. We exposed mammalian cells, transfected with a NF‐κB pathway‐controlled transcription system, to a range of microsecond‐duration pulsed electric field parameters. To prevent toxicity, we used protocols that would generate relatively mild physical stimulation. The present study, for the first time, proves the principle that microsecond‐duration pulsed electric fields can alter single‐gene expression in plasmid context in mammalian cells without significant damage to cell integrity or viability. Gene expression might be upregulated or downregulated depending on the cell line and parameters applied. This noninvasive, ligand‐, cofactor‐, nanoparticle‐free approach enables easily controlled direct electrostimulation of the construct carrying the gene of interest; the discovery may contribute towards the path of simplification of the complexity of physical systems in gene regulation and create further synergies between electronics, synthetic biology, and medicine. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. --//-- Citation: Kavaliauskaite, J.; Kazlauskaite, A.; Lazutka, J.R.; Mozolevskis, G.; Stirke, A. Pulsed Electric Fields Alter Expression of NF-κB Promoter Controlled Gene. Int. J. Mol. Sci. 2022, 23, 451. https://doi.org/10.3390/ijms23010451. Article published under the CC BY 4.0 license.Funding: A.S. acknowledges to the ERDF PostDoc project No. 1.1.1.2/VIAA/4/20/739. The Institute of Solid State Physics, University of Latvia (Latvia) as the Centre of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD01-2016-2017-Teaming Phase2 under grant agreement no. 739508, project CAMART2

NV microscopy of thermally controlled stresses caused by thin Cr2O3 films

Many modern applications, including quantum computing and quantum sensing, use substrate-film interfaces. Particularly, thin films of chromium or titanium and their oxides are commonly used to bind various structures, such as resonators, masks, or microwave antennas, to a diamond surface. Due to different thermal expansions of involved materials, such films and structures could produce significant stresses, which need to be measured or predicted. In this paper, we demonstrate imaging of stresses in the top layer of diamond with deposited structures of Cr2O3 at temperatures 19°C and 37°C by using stress-sensitive optically detected magnetic resonances (ODMR) in NV centers. We also calculated stresses in the diamond-film interface by using finite-element analysis and correlated them to measured ODMR frequency shifts. As predicted by the simulation, the measured high-contrast frequency-shift patterns are only due to thermal stresses, whose spin-stress coupling constant along the NV axis is 21±1 MHz/GPa, that is in agreement with constants previously obtained from single NV centers in diamond cantilever. We demonstrate that NV microscopy is a convenient platform for optically detecting and quantifying spatial distributions of stresses in diamond-based photonic devices with micrometer precision and propose thin films as a means for local application of temperature-controlled stresses. Our results also show that thin-film structures produce significant stresses in diamond substrates, which should be accounted for in NV-based applications. © 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement. --//-- This is an open access article Andris Berzins, Janis Smits, Andrejs Petruhins, Roberts Rimsa, Gatis Mozolevskis, Martins Zubkins, and Ilja Fescenko, "NV microscopy of thermally controlled stresses caused by thin Cr2O3 films," Opt. Express 31, 17950-17963 (2023), https://doi.org/10.1364/OE.489901.Centrālā finanšu un līgumu aģentūra (CFLA) (2.3.1.1.i.0/1/22/I/CFLA/001); European Regional Development Fund (ERAF) (1.1.1.5/20/A/001); Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase2 (739508, CAMART2); Latvijas Universitātes fonds ("Annealing furnace for the development of sensors", "Improvement of Magnetic field imaging system", "Simulations for stimulation of science"); Latvijas Zinātnes Padome (lzp-2020/2-0243, lzp-2021/1-0379); State Education Development Agency Republic of Latvia (1.1.1.2/VIAA/1/16/024)

Magnetotransport Studies of Encapsulated Topological Insulator Bi2Se3 Nanoribbons

This research was funded by the Latvian Council of Science, project “Highly tunable surface state transport in topological insulator nanoribbons”, No. lzp-2020/2-0343, and by the European Union’s Horizon 2020 research and innovation program, Grant Agreement No. 766714/ HiTIMe. Institute of Solid-State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.The majority of proposed exotic applications employing 3D topological insulators require high-quality materials with reduced dimensions. Catalyst-free, PVD-grown Bi2Se3 nanoribbons are particularly promising for these applications due to the extraordinarily high mobility of their surface Dirac states, and low bulk carrier densities. However, these materials are prone to the formation of surface accumulation layers; therefore, the implementation of surface encapsulation layers and the choice of appropriate dielectrics for building gate-tunable devices are important. In this work, all-around ZnO-encapsulated nanoribbons are investigated. Gate-dependent magnetotransport measurements show improved charge transport characteristics as reduced nanoribbon/substrate interface carrier densities compared to the values obtained for the as-grown nanoribbons on SiO2 substrates. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Latvian Council of Science lzp-2020/2-0343; H2020 Grant Agreement No. 766714; Institute of Solid-State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2

Lung on a Chip Development from Off-Stoichiometry Thiol–Ene Polymer

Institute of Solid-State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. Finally, we would like to thank Biol. Kaspars Tars from Latvian Biomedical research and study center for giving us the opportunity to participate in this consortium and contribute to Latvian scientists’ effort in response to the COVID-19 pandemic.Current in vitro models have significant limitations for new respiratory disease research and rapid drug repurposing. Lung on a chip (LOAC) technology offers a potential solution to these problems. However, these devices typically are fabricated from polydimethylsiloxane (PDMS), which has small hydrophobic molecule absorption, which hinders the application of this technology in drug repurposing for respiratory diseases. Off-stoichiometry thiol–ene (OSTE) is a promising alternative material class to PDMS. Therefore, this study aimed to test OSTE as an alternative material for LOAC prototype development and compare it to PDMS. We tested OSTE material for light transmission, small molecule absorption, inhibition of enzymatic reactions, membrane particle, and fluorescent dye absorption. Next, we microfabricated LOAC devices from PDMS and OSTE, functionalized with human umbilical vein endothelial cell (HUVEC) and A549 cell lines, and analyzed them with immunofluorescence. We demonstrated that compared to PDMS, OSTE has similar absorption of membrane particles and effect on enzymatic reactions, significantly lower small molecule absorption, and lower light transmission. Consequently, the immunofluorescence of OSTE LOAC was significantly impaired by OSTE optical properties. In conclusion, OSTE is a promising material for LOAC, but optical issues should be addressed in future LOAC prototypes to benefit from the material properties.--//--This work is licensed under a CC BY 4.0 license.This research was funded by project Nr. VPP-COVID-2020/1-0014 awarded by Latvian Council of Scienc

Extracellular Vesicles Isolation from Large Volume Samples Using a Polydimethylsiloxane-Free Microfluidic Device

Extracellular vesicles (EV) have many attributes important for biomedicine; however, current EV isolation methods require long multi-step protocols that generally involve bulky equipment that cannot be easily translated to clinics. Our aim was to design a new cyclic olefin copolymer–off-stoichiometry thiol-ene (COC–OSTE) asymmetric flow field fractionation microfluidic device that could isolate EV from high-volume samples in a simple and efficient manner. We tested the device with large volumes of urine and conditioned cell media samples, and compared it with the two most commonly used EV isolation methods. Our device was able to separate particles by size and buoyancy, and the attained size distribution was significantly smaller than other methods. This would allow for targeting EV size fractions of interest in the future. However, the results were sample dependent, with some samples showing significant improvement over the current EV separation methods. We present a novel design for a COC–OSTE microfluidic device, based on bifurcating asymmetric flow field-flow fractionation (A4F) technology, which is able to isolate EV from large volume samples in a simple, continuous-flow manner. Its potential to be mass-manufactured increases the chances of implementing EV isolation in a clinical or industry-friendly setting, which requires high repeatability and throughput

Bifurcated Asymmetric Field Flow Fractionation of Nanoparticles in PDMS-Free Microfluidic Devices for Applications in Label-Free Extracellular Vesicle Separation

Extracellular vesicles are small membrane-bound structures that are released by cells and play important roles in intercellular communication garnering significant attention in scientific society recently due to their potential as diagnostic and therapeutic tools. However, separating EVs from large-volume samples remains a challenge due to their small size and low concentration. In this manuscript, we presented a novel method for separating polystyrene beads as control and extracellular vesicles from large sample volumes using bifurcated asymmetric field flow fractionation in PDMS-free microfluidic devices. Separation characteristics were evaluated using the control system of polystyrene bead mix, which offers up to 3.7X enrichment of EV-sized beads. Furthermore, in the EV-sample from bioreactor culture media, we observed a notable population distribution shift of extracellular vesicles. Herein presented novel PDMS-free microfluidic device fabrication protocol resulted in devices with reduced EV-loss compared to size-exclusion columns. This method represented an improvement over the current state of the art in terms of EV separation from large sample volumes through the use of novel field flow fractionation design

Bifurcated Asymmetric Field Flow Fractionation of Nanoparticles in PDMS-Free Microfluidic Devices for Applications in Label-Free Extracellular Vesicle Separation

Extracellular vesicles are small membrane-bound structures that are released by cells and play important roles in intercellular communication garnering significant attention in scientific society recently due to their potential as diagnostic and therapeutic tools. However, separating EVs from large-volume samples remains a challenge due to their small size and low concentration. In this manuscript, we presented a novel method for separating polystyrene beads as control and extracellular vesicles from large sample volumes using bifurcated asymmetric field flow fractionation in PDMS-free microfluidic devices. Separation characteristics were evaluated using the control system of polystyrene bead mix, which offers up to 3.7X enrichment of EV-sized beads. Furthermore, in the EV-sample from bioreactor culture media, we observed a notable population distribution shift of extracellular vesicles. Herein presented novel PDMS-free microfluidic device fabrication protocol resulted in devices with reduced EV-loss compared to size-exclusion columns. This method represented an improvement over the current state of the art in terms of EV separation from large sample volumes through the use of novel field flow fractionation design