Institut für Photonische Technologien

Here we present a highly customisable image-based fuzzy logic control (FLC) method for pressure-driven droplet microfluidics. The system is designed to position droplets of different sizes in the centre of...

Mitochondria are intracellular organelles that act as powerhouses by breaking down nutrition molecules to produce adenosine triphosphate (ATP) as cellular fuel. They have their own genetic material called mitochondrial DNA. Alterations in mitochondrial DNA can result in primary mitochondrial diseases, including neurodegenerative disorders. Early detection of these abnormalities is crucial in slowing disease progression. With recent advances in data acquisition techniques such as focused ion beam scanning electron microscopy, it has become feasible to capture large intracellular organelle volumes at data rates reaching 4Tb/minute, each containing numerous cells. However, manually segmenting large data volumes (gigapixels) can be time-consuming for pathologists. Therefore, there is an urgent need for automated tools that can efficiently segment mitochondria with minimal user intervention. Our article proposes an ensemble of two automatic segmentation pipelines to predict regions of interest specific to mitochondria. This architecture combines the predicted outputs from both pipelines using an ensemble learning-based entropy-weighted fusion technique. The methodology minimizes the impact of individual predictions and enhances the overall segmentation results. The performance of the segmentation task is evaluated using various metrics, ensuring the reliability of our results. We used four publicly available datasets to evaluate our proposed method’s effectiveness. Our proposed fusion method has achieved a high score in terms of the mean Jaccard index and dice coefficient for all four datasets. For instance, in the UroCell dataset, our proposed fusion method achieved scores of 0.9644 for the mean Jaccard index and 0.9749 for the Dice coefficient. The mean error rate and pixel accuracy were 0.0062 and 0.9938, respectively. Later, we compared it with state-of-the-art methods like 2D and 3D CNN algorithms. Our ensemble approach shows promising segmentation efficiency with minimal intervention and can potentially aid in the early detection and mitigation of mitochondrial diseases.

A trajectory-tracked, near-infrared autofluorescence imaging guided, biochemical signature-projected needle-type Raman spectroscopy (TNBN-RS) system integrated on a medical cart was developed for rapid wide-field breast tissue stratification. A wide-field (10 × 10 cm²) near-infrared autofluorescence (NIRAF) imaging subsystem was developed for gross stratification of breast tissue types based on higher NIRAF intensity associated with breast cancer, followed by projection of NIRAF-identified breast tumor margins onto the tissue of interest with a compact projector. Raman spectra were further acquired from the NIRAF projected regions for confirmed margin assessment using a needle-type Raman probe equipped with color camera-based probe trajectory tracking. The trajectory of the Raman probe and the accompanying RS biochemical signature-based margin assessment were instantly projected. A unique field of view (FOV) calibration method was proposed to calibrate the TNBN-RS FOVs, resulting in a projection accuracy of <2 mm. A graphical user interface (GUI) was developed in C# for system control, real-time processing and display of NIRAF images, Raman spectra, and projection of their results. The performance of the TNBN-RS system was validated on an ex vivo breast tissue, demonstrating its potential for rapid intraoperative breast tumor margin assessment.

Optoacoustic or photoacoustic imaging (PA) combines optical excitation with acoustic readout, for non-invasive in vivo imaging at up to several centimetres' penetration depth, and down to micron resolution. Conceptually, many chromophore types can be used for simple anatomical PA, where signal generation is the only requirement: but few can perform the more complex task of molecular imaging of enzyme activity in practice, for which the many requirements include enzymatic signal switch-on. Here, we leverage molecular rotors to give a rational blueprint for high-performance small molecule PA contrast agents in the NIR/SWIR biotransparency window that offer straightforward adaptation for molecular imaging. According to our hypothesis, the ultrafast nonradiative S1→S0 kinetics (knr) of triphenylmethane rotors would be the chemical key to their PA signal (loudness) being strong, linear against imaging intensity, and outstandingly photostable. After we identified a route to shift typically the green/red absorbance of triarylmethanes into the NIR/SWIR, we showed that they are indeed >1000-fold more photostable as well as >5-fold louder than typical reference chromophores for PA. Pioneering femtosecond transient absorption spectroscopy results in live cells, as a bridge from spectroscopy to biology, supported our conceptual approach of maximising knr to optimise the several key practical aspects of PA performance. Much like molecular switches, molecular rotors had only been used in a limited scope of imaging modalities to date. This approach now shows the potential of rotors for quantitative longitudinal PA; and more broadly, the results will guide the future of mechanism-based design in rationally improving dye performance in a range of basic and translational imaging methods.

Background Antimicrobial resistance (AMR) in Enterobacterales constitutes a significant threat to the health of both humans and animals and a socioeconomic problem. Enterobacterales, mainly Escherichia coli, carrying β-lactamases has become one of the main indicators to estimate the burden of AMR in animals within “One Health” approach. Objectives To assess the presence of extended-spectrum cephalosporin-resistant Enterobacterales associated with ruminants (cattle, sheep, goats) habituated in all five provinces of Rwanda and to perform in depth characterization of isolates. Methods We screened 454 rectal swabs from 203 cows, 170 goats, and 81 sheep and selective isolation of extended-spectrum cephalosporin-resistant Enterobacterales was conducted. Isolates were identified as a members of the order Enterobacterales by MALDI-TOF MS and further characterized by susceptibility testing and by whole-genome sequencing. Results Out of the 454 samples, 64 extended-spectrum cephalosporin-resistant Enterobacterales were isolated from 58 animals. Isolates belonged to seven bacterial species and were identified as Escherichia coli (n = 54), Enterobacter bugandensis (n = 4), Enterobacter mori (n = 2), Klebsiella pneumoniae (n = 2), Enterobacter dykesii (n = 1), and Citrobacter freundii (n = 1). All isolates displayed an Extended-spectrum β-lactamases (ESBL) phenotype, with exception of Citrobacter freundii isolate displayed both an ESBL and AmpC phenotype. In addition, all Enterobacter isolates were identified as stably de-repressed AmpC-producers. ESBLs genes, blaCTX−M−15 was predominant. Resistance to tetracycline and tet(A) was most frequently observed among non-β-lactam resistance. Forty-eight isolates displayed multidrug-resistance phenotypes. A shiga toxin-producing E. coli and an enterotoxigenic E. coli isolate were observed. Genome comparisons revealed thirty-five E. coli sequence types (ST) (ST10, ST307 being predominate). Conclusions Considering the high proximity between ruminants and humans in Rwanda, the dissemination of antimicrobial drug resistance highlights the public health threats and requires the joint and multisectoral action of human and veterinary medicine, at human-animal-environment interfaces. Therefore, it is important to establish national and global “One Health” surveillance programs of AMR to tackle the antibiotic-resistant crisis in human and veterinary medicine.

The thermal sensitivity of fiber Bragg gratings (FBGs) is extensively employed in diverse industrial and scientific applications. FBGs lie at the core of flexible, low-cost, and highly precise sensors, featuring stability in harsh environments and distributed sensing capability. This study assesses the thermal properties of FBGs in fluoride fibers within a temperature range of 4–373 K. Despite having higher thermal expansion coefficients, FBGs in the near-IR wavelength range do not exhibit high sensitivity at room or higher temperatures. However, the pronounced enhancement of their thermal sensitivity at longer Bragg wavelengths shows the potential for sensing applications in the light of the fluoride glass extended transmission range up to 4–5.5 µm. Most importantly, employing FBGs inscribed in fluoride fibers enables the further expansion of fiber-based sensors to cryogenic environments, as they exhibit a detectable sensitivity of 0.5–1.7 pm/K below 50 K. Overall, the exposure to low temperatures provides valuable information on glass stability and physical parameters, which is beneficial for the further development of photonic systems based on fluoride fibers.

The post-mortem interval estimation for human skeletal remains is critical in forensic medicine. This study used Raman spectroscopy, specifically comparing a handheld device to a Raman microscope for PMI estimations. Analyzing 99 autopsy bone samples and 5 archeological samples, the research categorized them into five PMI classes using conventional methods. Key parameters—like ν1PO43− intensity and crystallinity—were measured and analyzed. A principal component analysis effectively distinguished between PMI classes, indicating high classification accuracy for both devices. While both methods proved reliable, the fluorescence interference presented challenges in accurately determining the age of archeological samples. Ultimately, the study highlighted how Raman spectroscopy could enhance PMI estimation accuracy, especially in non-specialized labs, suggesting the potential for improved device optimization in the field.

This study investigates supercontinuum generation in suspended core fibers filled with perfluorocarbons, highlighting their potential for ultrafast nonlinear frequency conversion. Spectroscopic absorption and refractive index dispersions are analyzed for three perfluorocarbons in the visible and near-infrared. Experiments show that the insertion of these liquids into suspended core fibers changes the dispersion landscape, enabling broadband soliton-based supercontinuum generation from 0.6 µm to 2.4 µm due to the creation of a confined domain of anomalous dispersion in the telecom range. In addition, temperature-dependent output spectrum modulation is demonstrated, highlighting the utility of the platform in photonic applications such as spectroscopy, sensing, and microscopy.

We aim to evaluate the feasibility of Raman spectroscopy for parathyroid gland (PG) identification during thyroidectomy. Using a novel side‐viewing handheld Raman probe, a total of 324 Raman spectra of four tissue types (i.e., thyroid, lymph node, PG, and lipid) commonly encountered during thyroidectomy were rapidly (< 3 s) acquired from 80 tissue sites (thyroid [ n = 10], lymph node [ n = 10], PG [ n = 40], lipid [ n = 20]) of 10 euthanized Wistar rats. Two partial least‐squares (PLS)‐discriminant analysis (DA) detection models were developed, differentiating the lipid and nonlipid (i.e., thyroid, lymph node, and PG) tissues with an accuracy of 100%, and PG, lymph node, and thyroid could be detected with an accuracy of 98.4%, 93.9%, and 95.4% respectively. This work demonstrates the feasibility of Raman spectroscopy technique for PG identification and protection during thyroidectomy at the molecular level.

Nanoparticles represent a heterogeneous collection of materials, whether natural or synthetic, with dimensions aligning in the nanoscale. Because of their intense manifestation with the immune system, they can be harvested for numerous bio-medical and biotechnological advancements mainly in cancer treatment. This review article aims to scrutinize various types of nanoparticles that interact differently with immune cells like macrophages, dendritic cells, T lymphocytes, and natural killer (NK) cells. It also underscores the importance of knowing how nanoparticles influence immune cell functions, such as the production of cytokines and the presentation of antigens which are crucial for effective cancer immunotherapy. Hence overviews of bio-molecular mechanisms are provided. Nanoparticles can improve antigen presentation, boost T-cell responses, and overcome the immunosuppressive tumor environment. The regulatory mechanisms, signaling pathways, and nanoparticle characteristics are also presented for a comprehensive understanding. We review the nanotechnology platform options and challenges in nanoparticles-based immunotherapy, from an immunotherapy perspective including precise targeting, immune modulation, and potential toxicity, as well as personalized approaches based on individual patient and tumor characteristics. The development of emerging multifunctional nanoparticles and theranostic nanoparticles will provide new solutions for the precision and efficiency of cancer therapies in next-generation practice.

The triplet excited state lifetime of a photosensitizer is an essential parameter for diffusion‐controlled energy‐ and electron‐transfer, which occurs usually in a competitive manner to the intrinsic decay of a triplet excited state. Here we show the decisive role of luminescence lifetime in the triplet excited state reactivity toward energy‐ and electron transfer. Anchoring two phenyl anthracene chromophores to a ruthenium(II) polypyridyl complex (RuII ref) leads to a RuII triad with a luminescence lifetime above 100 μs, which is more than 40 times longer than that of the prototypical complex. The obtained RuII triad sensitizes energy transfer to anthracene‐based annihilators more efficiently than RuII ref and enables red‐to‐blue photon upconversion with a pseudo anti‐Stokes shift of 0.94 eV and a moderate upconversion efficiency near 1 % in aerated solution. Particularly, RuII triad allows rapid photoredox catalytic polymerizations of acrylate and acrylamide monomers under aerobic condition with red light, which are kinetically hindered for RuII ref. Our work shows that excited state lifetime of a photosensitizer governs the dynamics of the excited state reactions, which seems an overlooked but important aspect for photochemistry.

Since the early 1990s, when researchers began to explore rare-earth-doped mid-infrared glass fibers, fiber laser systems have emerged as promising high-brightness light sources with wavelengths beyond 2.5 μm for applications in spectroscopy and sensing, optical communications and ranging, and processing of complex materials and bio-tissues, to name a few. Despite a substantial research effort over the years, mid-infrared fiber lasers and amplifiers have yet to reach the maturity required for widespread and/or industrial use. The well-known advantages of fiber lasers over their bulk counterparts, namely superior stability and beam quality, compactness, cost-efficiency, flexibility, and maintenance-free operation, can only be fully harnessed in the mid-infrared wavelength range with the development of non-existent yet essential fiber-based components made of advanced fluoride or chalcogenide-glass materials. This Perspective reports on the recent significant achievements that have been made in the design and fabrication of in-fiber and fiber-pigtailed components for fully integrated mid-infrared fiber laser systems. Building upon a comprehensive overview of the mechanical, thermodynamic, and optical properties of fluoride and chalcogenide glass fibers, as well as their interaction with light, we aim to highlight current challenges and opportunities and provide an informed forecast of future advancements in mid-infrared all-fiber laser research.

Despite the increasing demand for high-energy erbium lasers for LIDAR imaging applications, the scaling of the current Er-Yb co-doped technology is still hindered by a 1 µm parasitic emission. In this study, we present the first, to the best of our knowledge, utilization of the REPUSIL powder synthesis method to fabricate a 55 µm double-clad fiber with a remarkably large modal area. Doped solely with erbium and free of ytterbium, its estimated cladding absorption is 2 dB/m at 976 nm, enabling short amplification lengths. We demonstrate its potential through direct amplification of a GHz femtosecond laser (M² = 1.12) and notably, the generation of 1.8 mJ, 37 ns Q-switched pulses in oscillator configuration (M² = 1.46).

We propose a new way of deriving the effective thickness in attenuated total reflection (ATR) spectroscopy, initially introduced by Hansen and Harrick in 1965. While following Hansen's approach, our derivation is more straightforward and includes an intermediate approximation that more closely aligns with results derived from Fresnel's equations, particularly for organic and biological materials. Using this intermediate approximation, we present improved estimations for the effective thicknesses with s- and p-polarized light. These estimations enabled us to enhance a recently developed ATR correction scheme that relies on effective thickness. Additionally, we examined the wavelength dependence of the product of wavenumber and effective thickness, observing that it bears a resemblance to the refractive index function of the sample. This similarity increases with the angle of incidence and the refractive index of the ATR crystal. Based on this observation, we introduce a simple correction scheme using the Kramers–Kronig transformed absorbance. This correction has the potential to address spectral shifts, facilitating applications in pattern recognition and spectra identification.

Molecular charge accumulating systems that act as both, photosensitizer and electron storage unit, are of interest in the context of multielectron redox processes, e. g. in solar fuel production. To this end, the photophysical properties of RuL1, a ruthenium tris‐diimine complex with an alloxazine‐based ligand as bioinspired structural motif, were investigated. The study includes absorption, emission, resonance Raman and transient absorption spectroscopy in combination with quantum chemical simulations to determine the light‐driven reactivity of the complex. Moreover, spectroelectrochemistry was employed for an in‐depth characterization of the optical properties of the reduced complex. Finally, a photolysis experiment using triethanolamine as electron source, in conjunction with redox titrations, demonstrated that visible light irradiation triggers the formation of the doubly‐reduced singly‐protonated derivative of RuL1, where both redox equivalents are stored on the alloxazine‐based ligand.

This study explores the thermal conductivity of silicon nanowires arrays produced by metal-assisted chemical etching of silicon wafers with different dopants, doping levels and crystallography. The wide range of morphological structures observed in silicon nanowires strongly depends on the initial wafer characteristics, a factor that cannot be neglected. While previous studies have demonstrated the qualitative capabilities of photoacoustic and Raman spectroscopy in characterising nanostructured silicon, our work highlights the quantitative discrepancies that can arise when combining these techniques to investigate thermal properties. The differences in the results obtained using these methods can be attributed to the distinct nature of the information they provide: photoacoustic spectroscopy probes the effective thermal conductivity over larger areas, whereas Raman spectroscopy offers localized measurements. Furthermore, our Monte Carlo simulations provide insights into the morphological features of porous silicon that influence the interpretation of experimental data. This study underscores the importance of a comprehensive approach, combining both experimental and theoretical methods, to assess the thermal transport properties of nanostructured materials accurately.

This chapter presents a comprehensive review of the progress and innovations over the last ten years in microdevices that are based on surface-enhanced Raman spectroscopy (SERS) for point-of-care testing. It highlights both the advantages and shortcomings of microfluidic devices, lateral flow immunoassay (LFIA) strips, and three-dimensional nanostructured plasmonic substrates as key platforms for SERS in clinical diagnostics. While the integration of microfluidics with SERS provides high-throughput homogeneous analyte detection, LFIA enhance sensitivity and quantification. Not to mention the essential role that reliable and consistent SERS nanotags and substrates play in this regard. We conclude by discussing the challenges and future directions for the clinical adoption of SERS-based technologies, including but not limited to the necessity of collaboration and establishing unified protocols.

An innovative concept to achieve a self-starting, all-fibre and all-normal dispersion Mamyshev oscillator for the 1.9 μm wavelength domain is explored. A machine-aided approach is chosen to investigate systematically the constrictions between filter offset, output coupling ratio and pump power.