René Michel Rossi

Last Name

Rossi

First Name

René Michel

ORCID

0000-0003-0946-682X

Organisational unit

01630 - Lehre HEST

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Publications 1 - 10 of 19

Introduction to electrocardiogram signal quality assessment and estimated accuracy for textile electrodes
Martins , Neusa R. Adão; Bauer , Frederik; Baty , Florent; et al. (2025)
Scientific Reports
As the use of wearable electrocardiogram (ECG) data for modeling purposes continues to rise, there is a pressing need for signal quality assessment (SQA) algorithms capable of identifying segments of signal from which reliable data can be obtained. Manually annotated ECG data, obtained through expert visual inspection, is often used as reference in the development of ECG SQA algorithms. In this approach, the quality of a signal segment is assessed based on the level of noise present. Yet, the data extracted from noise-corrupted ECG signal segments might still be of sufficient accuracy depending on the target application. The current work proposes a paradigm shift by presenting a SQA algorithm that performs template matching and physiological feasibility checks to determine the quality of ECG signals acquired by textile-based wearable systems. Signal segments were classified into four different quality classes based on the estimated accuracy of RR intervals extracted from the signal segments of each class. Our findings show that the proposed SQA algorithm is effective in identifying ECG signal segments from which accurate RR intervals can be derived, and that the proportion of the data across the different classes is sensitive to different factors known to have an effect on signal quality.
Kidney stone classification by speckle x-ray imaging
Lindberg, Werneri A.; Richter, Henning; Alfayez, Fayez; et al. (2025)
Physics in Medicine and Biology
Objective. Urinary stone-related diseases affect approximately 6% of the global population, with nearly half of the patients experiencing recurrence. The diagnosis and management of the disease depend on the stone type and composition. Yet, current clinical imaging modalities (ultrasound, computed tomography, and radiography) lack the sensitivity and specificity required for accurate classification. Speckle-based dark-field x-ray imaging offers a potential non-invasive method for classifying urinary stones with the required hardware simplicity and robustness for potential in vivo, clinical applicability. However, the influence of diffuser masks and state-of-the-art speckle x-ray image retrievals on classification remains underexplored. Approach. This ex vivo study systematically compared the efficacy of custom diffuser masks and state-of-the-art speckle x-ray retrieval algorithms, using both grid and custom speckle masks, for single-shot dark-field imaging in urinary stone classification at high x-ray energy (80 kVp). Main Results. Among the various types of urinary stones examined in this study, canine ammonium urate showed the most distinct visibility contrast difference, deviating by 32 % from the average x-ray transmission value. Overall, the results indicate a potential to differentiate between three main groups of urinary stones based on their attenuation-to-scattering coefficients: ammonium urate, calcium-based stones, and a third group comprising cystine and struvite. Regarding the different diffuser masks, the periodic grid mask is found to be the most suitable candidate for application to urinary stones. The different dark-field visibility reduction retrieval algorithms yielded nearly identical classification trends for the urinary stone samples. We recommend nonetheless, the Fokker-Planck-based approach due to its strong physical basis and favorable image quality characteristics, especially if the noise level can be kept low. Significance. The findings in this study establish a technical foundation for advancing speckle-based dark-field x-ray imaging toward clinical translation for non-invasive urinary stone classification.
Polylactic acid green gels for fabrication of porous scaffolds
Wang, Wuchao; Rossi, René Michel; Wei, Kongchang (2025)
International Journal of Biological Macromolecules
Polylactic acid (PLA) has been approved for various medical devices and continues to attract significant interest in biomedical applications such as drug delivery, implants, and tissue engineering. As a thermoplastic polymer, PLA is typically processed either above its melting temperature or in solution. Herein, we developed a series of green solvent-based PLA organogels (termed PLA green gels), which enabled gel-based PLA processing. We investigated 20 bio-based green solvents for PLA dissolution through solubility parameter-based screening and experimental testing. Four bio-based solvents with low toxicity and high boiling points, namely ethyl lactate (EL), gamma-valerolactone (GVL), dihydrolevoglucosenone (Cyrene™), and dimethyl isosorbide (DMI), were identified as promising candidates for the preparation of PLA green gels. Sol-gel transition, rheological and structural properties of the PLA green gels were thoroughly characterized. Subsequently, porous PLA scaffolds were fabricated from such PLA green gels via injection molding and solvent exchange. Our results have demonstrated the potential of green gel-based PLA manufacturing. More importantly, two distinct solvent-dependent gelation mechanisms were revealed for future PLA biomaterial development: phase separation-induced rapid gelation (in EL and GVL), which resulted in stiff and brittle scaffolds, and crystallization-induced slow gelation (in Cyrene™ and DMI), which produced soft and compliant scaffolds.
Innovative air mattress for the prevention of pressure ulcers in neonates
Jucker, Tino; Annaheim, Simon; Morlec, Elodie; et al. (2024)
Journal of Wound Care
Objective: Pressure ulcers (PUs) severely impact health outcomes in neonatal intensive care, with up to 28% prevalence and doubled mortality rates. Due to their only partially developed stratum corneum, neonates are highly susceptible to PUs because of a lack of adequate support surfaces. The occipital region of the head and hip are the main risk areas due to immobility and newborn body proportions. The main goal of the study was to investigate the impact of reduction in local pressure in these body areas by two air mattress designs and different filling states. Method: Two innovative air-filled mattress prototypes (prototype 1 and prototype 2), consisting of three different segments (head, trunk and feet regions), were developed to reduce local interface pressures by optimising pressure distribution, and were assessed with three air pressure filling states (0.2kPa, 0.4kPa and 0.6kPa). A baby doll was used to investigate pressure distribution and local pressure impact. It measured 51cm and the weight was modified to be 1.3kg, 2.3kg and 3.3kg, representing premature to term newborn weights, respectively. A specialised foam mattress and an unsupported surface were considered as controls. Results: The interface pressures at the hip region for newborn models could be reduced by up to 41% with mattress prototype 1 and 49% with prototype 2 when filled with 0.2kPa air pressure. It was found that the size and the pressure inside air segments was crucial for interface pressure. Conclusion: Our results demonstrated that air mattresses achieved lower interface pressures compared to conventional support surfaces, and that the benefit of the air mattresses depended on their filling status. The importance of using innovative, segmented designs that were tailored to meet the specific needs of highly vulnerable paediatric patients was demonstrated.
Wicking fingering in electrospun membranes
Fischer, Robert; Schoeller, Jean; Rossi, René Michel; et al. (2022)
Soft Matter
Pronounced fingering of the waterfront is observed for in-plane wicking in thin, aligned electrospun fibrous membranes. We hypothesize that a perturbation in capillary pressure triggers the onset of fingering, which grows in a non-local manner based on the waterfront gradient. Vertical and horizontal wicking in thin electrospun membranes of poly(ethylene-co-vinyl alcohol) (EVOH) fibers with varying fiber alignment and degree of orientation is studied with backlight photography. A non-local transport model considering the gradient of the waterfront is developed, where fiber orientation is modeled with a correlated random field. The model shows that a transition from straight to highly fingered waterfront occurs during water uptake as observed in the experiment. The size and shape of the fingers depend on fiber orientation. Based on good model agreement, we show that, during wicking in thin electrospun membranes, fingering is initially triggered by a perturbation in capillary pressure caused by the underlying anisotropic and heterogeneous membrane structure which grows in a non-local manner depending on the waterfront gradient.
Development of a Textile Integrated, Two-State Controlled Tremor Suppression Orthosis for the Wrist
Fromme, Nicolas P.; Esser, Adrian; Camenzind, Martin; et al. (2023)
IEEE Transactions on Medical Robotics and Bionics
Tremor is one of the most common movement disorders with the highest prevalence in the upper limb. Apart from medication or surgery, the mechanical suppression of the involuntary movement with an orthosis can be used as alternative treatment. Here we propose a controlled energy dissipating suppression orthosis using a mechanical brake. For this approach, we focused on improved wearability with voluntary movement preservation and ergonomics while providing tremor suppression. The novelty of this orthosis is the decentralization of the tremor suppression mechanism and the integration of textiles in the orthosis structure. We performed computational and test bench simulations of a controlled two-state brake with a 1D human model to optimize the brake duration and timing. The objective was to optimize the trade-off between tremor suppression and voluntary movement suppression. The textile-integrated prototype, with the optimized parameter, was validated in a proof-of-concept case study with a tremor-affected person performing activities of daily living. With the optimized parameters, we achieved a tremor suppression of 78.8%, 66.5%, and 40.8% for the simulation, test bench, and case study, respectively as measured by the change in power spectral density (PSD) at the tremor frequency peak. While minimizing the voluntary movement suppression in the simulation and test bench by introducing the trajectory distance as new validation method (23.7% and 31.2%), no voluntary movements suppression was measured in the case study using PSD analysis. Our new orthosis has the potential to become a daily wearable device that can improve the quality of life for tremor-affected people.
Human body-interfacing material strategies for personal thermal and moisture management of wearable systems
Guan, Manhao; Wang, Gang; Li, Jun; et al. (2023)
Progress in materials science
Personal thermal and moisture management for wearable systems and strategies are drawing increasing attention due to their potential on human thermal comfort and safety and energy saving, especially in the era of climate change and energy shortage. Various studies have been conducted on personal thermal and moisture management via wearable systems and strategies. Wearable systems for personal thermal and moisture regulation, aiming at the improvement of human comfort and safety and energy saving, are being under a new round of development with novel materials. Wearable systems for personal thermal and moisture conversion are emerging as energy strategies for energy regeneration, along with the wide development of wearable electronics. Although these wearable systems and strategies have usually been investigated as separate topics thus far, they are closely related with each other since they significantly interact with body heat and moisture and impact the thermal safety of “human body-wearable systems”. Meanwhile, limitations exist in the evaluation approaches for personal thermal and moisture management of these emerging wearable systems. In this review, recent progress of material strategies and performance for personal thermal and moisture management of wearable systems, and the performance evaluation approaches, are discussed to provide a fundamental and comprehensive perspective for the personal thermal and moisture management of wearable systems. Future research directions for personal thermal and moisture management of wearable systems are proposed with the aim to improve the global human health and safety in the context of climate extremes and energy shortage.
Use of a novel pressure distribution system for severely ill neonates: a clinical pilot study carried out by the PREPICare consortium
Schlüer, Anna-Barbara; Müller, Adrian Yves; Fromme, Nicolas Philip; et al. (2023)
BMC Pediatrics
Background: Pressure Injuries are not exclusively an adult phenomenon; various risk factors contribute to a high prevalence rate of 43% in the neonatal and pediatric intensive care population. Effective preventive measures in this population are limited. Methods: We performed a pilot study to analyze the distribution and localization of support surface interface pressures in neonates in a pediatric intensive care unit (PICU). The hypothesis was that pressure redistribution by a novel air mattress would reduce pressure peaks in critical neonates. The measurements were conducted in a 27-bed level III PICU between November and December 2020. This included measuring pressure distribution and pressure peaks for five neonates positioned on either a state-of-the-art foam mattress or a new prototype air mattress. Results: We confirmed that the pressure peaks were significantly reduced using the prototype air mattress, compared with the state-of-the-art foam mattress. The reduction of mean pressure values was 9–29%, while the reduction of the highest 10% of pressure values was 23–41%. Conclusions: The journey to an effective, optimal, and approved product for severely ill neonates to reduce Pressure Injuries is challenging. However, a crucial step was completed by this pilot study with the first pressure measurements in a real-world setting and the successful realization of a decrease in pressure peaks obtained using a prototype air mattress.
Energy harvesting textiles: using wearable luminescent solar concentrators to improve the efficiency of fiber solar cells
Huang, Chieh-Szu; Kang, Xinyue; Rossi, René Michel; et al. (2021)
Journal of Materials Chemistry A
Fiber solar cells have attracted considerable interest in recent years for their agile integration with wearable electronics. They have the unique advantage of collecting light from all directions. However, in daily use, the incoming sunlight only covers the face-up surface area and a large portion of it is lost between fiber gaps, leading to an unexploited device efficiency. In this work, wearable luminescent solar concentrators (LSCs) are integrated with fiber solar cells to harvest additional photons and fully utilize the advantage of harvesting light from all directions. Wearable LSCs made from an amphiphilic polymer conetwork matrix and coumarin 6 luminescent dyes are applied to fiber dye-sensitized solar cells (FDSSCs). The results show a remarkable FDSSC power conversion efficiency enhancement of 84%, LSC concentration factor of 1.57, and device optical efficiency of 7.85%, attributed to LSC-assisted enlargement of the photon harvesting area, recycling of lost photons, and utilization of the complete surface of FDSSCs. Using a Monte Carlo ray-tracing simulation for optimizing the fibers' arrangement, a textile with multiple FDSSCs integrated with 3 cm² LSCs exhibits a high-power output of 0.89 mW. The device shows a sustainable power conversion efficiency even after 1000 bending cycles, which demonstrates its wearability. This is the first experimental and computational demonstration of the integration of FDSSCs and wearable LSCs as energy harvesting textiles, showcasing their potential as future wearable electronic systems.
Amphiphilic Polymer Co-Network: A Versatile Matrix for Tailoring the Photonic Energy Transfer in Wearable Energy Harvesting Devices
Huang, Chieh-Szu; Yakunin, Sergii; Avaro, Jonathan; et al. (2022)
Advanced Energy Materials
In recent years, Förster resonance energy transfer (FRET) and related topics have received marked attention both as a subject of scientific investigation and due to its many potential applications. However, the state-of-the-art matrix materials for the FRET need to be improved in terms of universal loading for all types of luminescent moieties and the matrix integrability with real-life devices, but without sacrificing the FRET efficiency, i.e., maintaining the proximity of the embedded donors and acceptors. Amphiphilic polymer co-networks (APCNs) are investigated as versatile matrix materials for hosting luminescent materials and realizing highly efficient FRET between hydrophobic inorganic donors (CsPbBr3 nanocrystals) and hydrophilic organic acceptors (Rhodamine B). APCNs are advantageous owing to the unique properties of their hydrophilic and hydrophobic biphasic nature and the uniformly distributed nano-domains. The energy transfer rate can be tailored in a straightforward way by manipulating the nano-domain sizes and volumetric distribution, so steering donor–acceptor pair loading and distances. Consequently, APCNs are used as luminescent solar concentrators for fiber solar cells, demonstrating the ability to enhance existing solar-energy harvesting electronics via photonic energy transfer steering. APCN is demonstrated as a powerful matrix for future photonic applications in the field of energy harvesting and energy generation.

Publications 1 - 10 of 19

René Michel Rossi

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