Stretchable and Skin-Conformable Conductors Based on Polyurethane/Laser-Induced Graphene

The conversion of various polymer substrates into laser-induced graphene (LIG) with a CO2 laser in ambient condition is recently emerging as a simple method for obtaining patterned porous graphene conductors, with a myriad of applications in sensing, actuation, and energy. In this paper, a method is presented for embedding porous LIG (LIG-P) or LIG fibers (LIG-F) into a thin (about 50 μm) and soft medical grade polyurethane (MPU) providing excellent conformal adhesion on skin, stretchability, and maximum breathability to boost the development of various unperceivable monitoring systems on skin. The effect of varying laser fluence and geometry of the laser scribing on the LIG micro-nanostructure morphology and on the electrical and electromechanical properties of LIG/MPU composites is investigated. A peculiar and distinct behavior is observed for either LIG-P or LIG-F. Excellent stretchability without permanent impairment of conductive properties is revealed up to 100% strain and retained after hundreds of cycles of stretching tests. A distinct piezoresistive behavior, with an average gauge factor of 40, opens the way to various potential strain/pressure sensing applications. A novel method based on laser scribing is then introduced for providing vertical interconnect access (VIA) into LIG/MPU conformable epidermal sensors. Such VIA enables stable connections to an external measurement device, as this represents a typical weakness of many epidermal devices so far. Three examples of minimally invasive LIG/MPU epidermal sensing proof of concepts are presented: as electrodes for electromyographic recording on limb and as piezoresistive sensors for touch and respiration detection on skin. Long-term wearability and functioning up to several days and under repeated stretching tests is demonstrated

Comparison of matching layers for automotive radome design

Hidden integration of 79 GHz sensors behind plastic and painted fascia represents a challenging task since both electromagnetic and car body design constraints have to be met. This paper compares different possibilities for low-cost integration of radar sensors. Based on a model for stratified media, a study of the most important parameters such as bandwidth, angle and tolerances is shown. Our results suggest that for plastic fascia, the requirements of future radar sensors can be met with low-cost matching. Even with metallic paints, the requirements imposed by modern 79 GHz radar sensors can be met under certain conditions

Comparison of Wash-out Properties after Use of the Vital Dye Trypan Blue in the Form of an Ophthalmic Dye and Bound in a Sodium Hyaluronate by Raman Spectroscopy

In cataract surgery, the creation of the anterior capsulorhexis as one of the critical steps is of most importance for the surgical success. In challenging initial situations (e.g. in eyes with pseudoexfoliation syndrome, mature, brunescent cataract, juvenile cataract, corneal opacities, or in post-traumatic and postuveitic cases), vital dyes are used as a routine to increase the visibility and plasticity of the ocular structures in the anterior chamber. The range of applications of the vital dye trypan blue (TB) has expanded considerably in recent years due to its excellent staining properties.1 However, its use in ophthalmology as an effective and useful tool requires that the dye has no adverse effects on the cell structures of the eye. As two laboratory studies on cell cultures showed, the time of exposure to TB plays an important role in addition to concentration.2,3 The in vitro studies by Chang et al. with rabbit corneal endothelial cell cultures, and van Dooren et al.3 demonstrated no toxicity of TB with a maximum concentration of 0.4% after 1 minute in cell cultures of human corneal fibroplasts. A significant toxicity of a TB concentration of 0.01% or higher after exposure was observed. At 24-hour exposure, a TB concentration of 0.005% was found to be the threshold for a significant cytotoxicity index. In principle, it is important to note that trypan blue can be cytotoxic at a certain concentration. Monoazo, the most toxic of known impurities found in trypan blue dyes can be carcinogenic. However, the TB concentrations used in eye surgery do not have undesirable effects on the cell structures of the eye and are therefore generally considered safe.3,4 However, a case report showed a transient retinal toxic reaction in the form of transient visual field defect following the entry of TB into the vitreous body space.5 In modern intraocular procedures viscoelastic substances (OVDs, ophthalmic viscoelastic devices) are widely used. Since their introduction in the 1970s, they have been routinely used in cataract surgery and serve to protect sensitive eye structures from mechanical injuries or to create and maintain anatomical spaces such as the anterior chamber or the capsular bag. They increase safety during the procedure and can also shorten overall surgery time by improving visibility and simplifying some surgical steps for the surgeon.6 A shorter surgery time is associated with a lower degree of trauma and a lower risk of complications, and may ultimately be associated with faster recovery and a better final outcome and satisfaction for the patient. In addition, from an economic point of view, the time saving factor is particularly important for high-volume facilities. After the introduction of Healon® in 1979, sodium hyaluronate became the most widely used biopolymer for OVDs in intraocular surgery. Since then, the pharmacological, physiological, and clinical aspects of sodium hyaluronate for ophthalmic applications have been assessed in a large number of studies.7,8 Recently, a combination of a viscoelastic with the vital dye TB has been introduced (Pe-Ha-Blue®PLUS, Albomed, Schwarzenbruck, Germany) and has already been clinically investigated in a prospective case series of 52 eyes with pseudoexfoliation syndrome.6 In addition to a significantly shorter surgery time (due to fewer individual surgical steps) with cost- and safety-relevant advantages of Pe-Ha-Blue®PLUS compared to separate administration of OVD (POLY-HYL® 1. 6%; Polytech Domilens GmbH) and TB (Vision Blue®; DORC, Holland/Blue Color Caps®), the surgeon gains better control over whether the OVD is removed completely at the end of surgery by using the blue OVD. This should also reduce postoperative complications such as hypertension due to OVD residues remaining in the eye. The aim of the present in vitro study was to determine by Raman spectroscopy the amount of residue of the TB dye that remains on a slide during the routine application of two commercial products (TB dye Vision Blue® and Pe-Ha-Blue®PLUS). In Raman spectroscopy, the interaction of light and matter is used to investigate, for example, the properties of a material or to enable the microscopic examination of materials. Excited by monochromatic light, the sample emits scattered light with a specific frequency shift. The frequency shift (the so-called Raman shift) contain information about the vibrational states of the molecules and thus about the chemical composition and structure of the sample. This phenomenon was discovered by Sir C. V. Raman in the early 20th century. Since the beginning of the 20th century, the method, today mostly stimulated by a laser light source, is widely used in fields such as industry, chemistry, archaeology or for the qualitative and quantitative analysis of products in the pharmaceutical industry

Pedestrian recognition using automotive radar sensors

The application of modern series production automotive radar sensors to pedestrian recognition is an important topic in research on future driver assistance systems. The aim of this paper is to understand the potential and limits of such sensors in pedestrian recognition. This knowledge could be used to develop next generation radar sensors with improved pedestrian recognition capabilities. A new raw radar data signal processing algorithm is proposed that allows deep insights into the object classification process. The impact of raw radar data properties can be directly observed in every layer of the classification system by avoiding machine learning and tracking. This gives information on the limiting factors of raw radar data in terms of classification decision making. To accomplish the very challenging distinction between pedestrians and static objects, five significant and stable object features from the spatial distribution and Doppler information are found. Experimental results with data from a 77 GHz automotive radar sensor show that over 95% of pedestrians can be classified correctly under optimal conditions, which is compareable to modern machine learning systems. The impact of the pedestrian's direction of movement, occlusion, antenna beam elevation angle, linear vehicle movement, and other factors are investigated and discussed. The results show that under real life conditions, radar only based pedestrian recognition is limited due to insufficient Doppler frequency and spatial resolution as well as antenna side lobe effects

V-Edge: Virtual Edge Computing as an Enabler for Novel Microservices and Cooperative Computing

As we move from 5G to 6G, edge computing is one of the concepts that needs revisiting. Its core idea is still intriguing: Instead of sending all data and tasks from an end user's device to the cloud, possibly covering thousands of kilometers and introducing delays lower-bounded by propagation speed, edge servers deployed in close proximity to the user (e.g., at some base station) serve as proxy for the cloud. This is particularly interesting for upcoming machine-learning-based intelligent services, which require substantial computational and networking performance for continuous model training. However, this promising idea is hampered by the limited number of such edge servers. In this article, we discuss a way forward, namely the V-Edge concept. V-Edge helps bridge the gap between cloud, edge, and fog by virtualizing all available resources including the end users' devices and making these resources widely available. Thus, V-Edge acts as an enabler for novel microservices as well as cooperative computing solutions in next-generation networks. We introduce the general V-Edge architecture, and we characterize some of the key research challenges to overcome in order to enable wide-spread and intelligent edge services

Inertial sensing with quantum gases: a comparative performance study of condensed versus thermal sources for atom interferometry

Abstract: Quantum sensors based on light pulse atom interferometers allow for measurements of inertial and electromagnetic forces such as the accurate determination of fundamental constants as the fine structure constant or testing foundational laws of modern physics as the equivalence principle. These schemes unfold their full performance when large interrogation times and/or large momentum transfer can be implemented. In this article, we demonstrate how interferometry can benefit from the use of Bose–Einstein condensed sources when the state of the art is challenged. We contrast systematic and statistical effects induced by Bose–Einstein condensed sources with thermal sources in three exemplary science cases of Earth- and space-based sensors. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s)

Machine Learning for QoS Prediction in Vehicular Communication: Challenges and Solution Approaches

As cellular networks evolve towards the 6th generation, machine learning is seen as a key enabling technology to improve the capabilities of the network. Machine learning provides a methodology for predictive systems, which can make networks become proactive. This proactive behavior of the network can be leveraged to sustain, for example, a specific quality of service requirement. With predictive quality of service, a wide variety of new use cases, both safety- and entertainment-related, are emerging, especially in the automotive sector. Therefore, in this work, we consider maximum throughput prediction enhancing, for example, streaming or high-definition mapping applications. We discuss the entire machine learning workflow highlighting less regarded aspects such as the detailed sampling procedures, the in-depth analysis of the dataset characteristics, the effects of splits in the provided results, and the data availability. Reliable machine learning models need to face a lot of challenges during their lifecycle. We highlight how confidence can be built on machine learning technologies by better understanding the underlying characteristics of the collected data. We discuss feature engineering and the effects of different splits for the training processes, showcasing that random splits might overestimate performance by more than twofold. Moreover, we investigate diverse sets of input features, where network information proved to be most effective, cutting the error by half. Part of our contribution is the validation of multiple machine learning models within diverse scenarios. We also use explainable AI to show that machine learning can learn underlying principles of wireless networks without being explicitly programmed. Our data is collected from a deployed network that was under full control of the measurement team and covered different vehicular scenarios and radio environments.Comment: 18 pages, 12 Figures. Accepted on IEEE Acces