Formation mechanisms of flexible strain-sensitive sensors based on carbon nanostructures with laser formation for a post-traumatic joint rehabilitation monitoring system

Flexible sensors composed of carbon nanostructures and elastic materials have been developed for healthcare monitoring, environmental monitoring, disposable biochemical or electrochemical sensors, and many other applications. Fabrication approaches for such sensors and their advantages and current issues related to patterning high‐performance flexible sensors are reviewed. A focus is placed on patterning techniques for carbon‐based flexible sensors including carbon nanotubes, graphene, and other carbon nanostructures. First, novel patterning techniques for nanomaterials are described, along with their current challenges. Next, emerging flexible sensors including humidity, temperature, strain, and pressure sensors are discussed. Finally, the challenges and perspectives for flexible sensors are addressed.

Purpose The purpose of this paper is to introduce a variable distance pneumatic gripper with embedded flexible sensors, which can effectively grasp fragile and flexible objects. Design/methodology/approach Based on the motion principle of the three-jaw chuck and the pneumatic “fast pneumatic network” (FPN), a variable distance pneumatic holder embedded with a flexible sensor is designed. A structural design plan and preparation process of a soft driver is proposed, using carbon nanotubes as filler in a polyurethane (PU) sponge. A flexible bending sensor based on carbon nanotube materials was produced. A static model of the soft driver cavity was established, and a bending simulation was performed. Based on the designed variable distance soft pneumatic gripper, a real-time monitoring and control system was developed. Combined with the developed pneumatic control system, gripping experiments on objects of different shapes and easily deformable and fragile objects were conducted. Findings In this paper, a variable-distance pneumatic gripper embedded with a flexible sensor was designed, and a control system for real-time monitoring and multi-terminal input was developed. Combined with the developed pneumatic control system, a measure was carried out to measure the relationship between the bending angle, output force and air pressure of the soft driver. Flexible bending sensor performance test. The gripper diameter and gripping weight were tested, and the maximum gripping diameter was determined to be 182 mm, the maximum gripping weight was approximately 900 g and the average measurement error of the bending sensor was 5.91%. Objects of different shapes and easily deformable and fragile objects were tested. Originality/value Based on the motion principle of the three-jaw chuck and the pneumatic FPN, a variable distance pneumatic gripper with embedded flexible sensors is proposed by using the method of layered and step-by-step preparation. The authors studied the gripper structure design, simulation analysis, prototype preparation, control system construction and experimental testing. The results show that the designed flexible pneumatic gripper with variable distance can grasp common objects.

Continuous blood pressure monitoring in everyday life is important and necessary to detect and control high blood pressure in advance. While the existing blood pressure monitoring techniques are well suited for applications in current clinical settings, they are inadequate for next-generation wearable long-term monitoring of blood pressure on a daily basis. In this study, a flexible piezo-composite ultrasonic sensor was reported, for the first time, for continuous blood pressure measurement through ultrasonic motion tracking of blood vessel wall. A flexible piezo-composite ultrasonic sensor was designed and fabricated with a layer of PZT-5A/ polydimethylsiloxane (PDMS) anisotropic 1-3 composite and silver nanowire based stretchable electrodes. The material properties and dimensions of the sensor were determined according to the volume fraction of PZT-5A and the material properties of PZT-5A and PDMS. The experimental results illustrated that the flexible sensor possessed adequate bandwidth and sensitivity for blood pressure monitoring. Continuous blood pressure measurement was successfully conducted with the ulnar artery on a volunteer's right arm. Compared with the measurement results using a clinical ultrasound probe and a commercial upper arm blood monitor, the results obtained in this study demonstrated the capability of the proposed flexible sensor to continuously monitor blood pressure waveforms during cardiac cycles. The flexible sensor provides a promising solution for noninvasive, nonocclusive and calibration-free blood pressure monitoring. It has great potential to be integrated into a wearable ultrasonic healthcare sensing system for blood pressure and flow monitoring.

Flexible, light‐weight, and wearable electronics have significant potential for the development of Internet of Things. Flexible sensors with tunable piezoresistive properties are in high demand for various practical applications. Herein, different morphology thermoplastic polyurethane (TPU)/ carbon nanostructure (CNS) composites with segregated network are obtained by swelling the TPU powders using various solvents. The better solvent for TPU, dimethylformamide (DMF), renders the composites with 0.7 wt% CNS stronger polymer‐filler interactions, resulting in significantly improved piezoresistive sensitivity at strain larger than 150%. Also the gauge factors (GFs) for these composites are 9.7 in the range 0–60% strain and 19.3 for 60–100% strain. In contrast, the composites with ethanol (EtOH) and tetrahydrofuran (THF) which swell less the TPU show delayed increase in piezoresistivity and GFs of 2.2 and 3.5 for strain up to 100%, respectively, suggesting potential applications for stretchable conductors.

Numerical modelling of non-premixed biogas and LPG combustion to study carbon nanostructures formation in flame

The phenomenon of magnetism is one of the key components of today's technological progress. Magnetic interactions and magnetic materials are essential for the scientific disciplines of physics, chemistry and biology, making this subject truly multidisciplinary. This thesis is devoted to magnetic properties of two classes of substances. The first class represents the complexes of the ions of paramagnetic metals, primarily of the gadolinium(III) ion. These molecular compounds have an important application as magnetic resonance imaging (MRI) contrast agents for medical diagnostics. The design of more efficient MRI contrast agents requires a detailed knowledge of their magnetic properties. The other part of the thesis considers the broad class of recently discovered carbon nanostructures and materials. Their extraordinary physical properties foretell future applications of these materials in electronics, medicine and other fields. For instance, carbon nanotubes loaded with gadolinium(III) ion clusters are highly efficient MRI contrast agents. By using accurate density functional theory calculations in combination with classical molecular dynamics simulations, we determine hyperfine and quadrupole coupling constants on the nuclei of a first coordination sphere water molecule in gadolinium(III) aqua complexes. These parameters play a crucial role in the description of the key function, relaxivity, of MRI contrast agents. We found that the spin-polarization effect induced by the paramagnetic gadolinium(III) ion results in a Fermi contact hyperfine coupling of both the 1H and 17O nuclear spins and affects the dipole hyperfine coupling of the 17O nuclear spin of the inner coordination sphere water molecule. The 17O quadrupole coupling parameters of a coordinated water molecule are found to be very similar to that of neat water. We also apply the methodology of first principles molecular dynamics in order to perform realistic simulations of paramagnetic metal ions in water solution. This allows us to assess structure, dynamics and hyperfine interactions on the water molecules in the inner and outer coordination spheres of two metal ions: chromium(III) and gadolinium(III). In order to perform such calculations, we develop a novel approach for the evaluation of hyperfine coupling constants in pseudopotential electronic structure techniques. Our method takes into account the contribution of core electrons. In the second part of the thesis, we consider magnetic properties of a broad class of carbon nanostructures derived from two-dimensional graphene. We find that in metallic carbon nanotubes, an isotropic Knight shift, a hyperfine contribution to the nuclear magnetic resonance chemical shift, shows a regular dependence on the nanotube diameter. By using a more general approach, we reveal systematic dependences of magnetic interactions between arbitrarily distributed spin-polarized conduction electrons and nuclear spins in the carbon nanostructures derived from graphene. This knowledge is important for interpreting the results of magnetic resonance experiments and for evaluating the performance of carbon nanostructures as materials for alternative approaches in electronics, spintronics and quantum information processing based on electron and nuclear spins. In addition, we study magnetism in graphene induced by single-atom defects. The predicted itinerant magnetism due to the defect-induced states in graphenic materials may account for the experimental observations of ferromagnetism in irradiated graphite which has potential applications in technology. Finally, our first principles molecular dynamics study reveals the mechanisms of the irradiation-induced defect formation. We show that certain defect structures in layered carbon materials can be created selectively by irradiation at predefined conditions.

Flexible sensors are essential components in emerging fields such as epidermal electronics, biomedicine, and human-computer interactions, and creating high-performance sensors through simple structural design for practical applications is increasingly needed. Presently, challenges still exist in establishing efficient models of flexible piezoresistive pressure sensors to predict the design required for achieving target performance. This work establishes a theoretical model of a flexible pressure sensor with a simple laminated and enclosed structure. In the modeling, the electrical constriction effect is innovatively introduced to explain the sensitization mechanism of the laminated structure to a broad range of pressures and to predict the sensor performance. The experimental results confirmed the effectiveness of the theoretical model. The sensor exhibited excellent stability for up to three million cycles and superior durability when exposed to salt solution owing to its simple laminated and enclosed structural design. Finally, a wearable sensing system for real-time collection and analysis of plantar pressure is constructed for exercise and rehabilitation monitoring applications. This work aims to provide theoretical guidance for the rapid design and construction of flexible pressure sensors with target performance for practical applications.

We review our quantum chemical molecular dynamics (QM/MD)-based studies of carbon nanostructure formation under nonequilibrium conditions that were conducted over the past 10+ years. Fullerene, carbon nanotube, and graphene formation were simulated on the nanosecond time scale, considering experimental conditions as closely as possible. An approximate density functional method was employed to compute energies and gradients on the fly in direct MD simulations, while the simulated systems were pushed away from equilibrium via carbon concentration or temperature gradients. We find that carbon nanostructure formation from feedstock particles involves a phase transition of sp to sp2 carbon phases, which begins with the formation of Y-junctions, followed by a nucleus consisting of pentagons, hexagons, and heptagons. The dominance of hexagons in the synthesized products is explained via annealing processes that occur during the cooling of the grown carbon structure, accelerated by transition-metal catalysts when present. The dimensional structures of the final synthesis products (0D~spheres – fullerenes, 1D tubes – nanotubes, 2D sheets – graphenes) are induced by the shapes of the substrates/catalysts and their interaction strength with carbon. Our work prompts a paradigm shift away from traditional anthropomorphic formation mechanisms solely based on thermodynamic stability. Instead, we conclude that nascent carbon nanostructures at high temperatures are dissipative structures described by nonequilibrium dynamics in the manner proposed by Prigogine, Whitesides, and others. As such, the fledgling carbon nanostructures consume energy while increasing the entropy of the environment and only gradually anneal to achieve their familiar, final structure, maximizing hexagon formation wherever possible.

Multifunctional polyether block amides/carbon nanostructures piezoresistive foams with largely linear range, enhanced and humidity-regulated microwave shielding

Polymer/CNT nanocomposites as piezoresistive films provide an innovative approach for the realization of scalable strain sensors with high sensitivity and low manufacturing costs. These nanocomposites can be realized by thin film deposition or printing techniques on flexible substrates, e.g. foils, mats and textiles, and lead to flexible functional layers. Depending on the sensor geometry the sensing layers allow the strain measurement of integral measurements and local measurement at a certain position. Strain sensors based on carbon nanostructures can overcome several limitations of conventional strain sensors and provide interesting advantages, e.g. high sensitivity, adjustable measurement range and integral measurement on large surfaces. Some of these aspects will be exemplarily discussed for CNT/epoxy and CNT/PEDOT: PSS nanocomposites. Owing to their aforementioned features, CNT based flexible strain sensors are highly attractive for applications in the fields of structural health monitoring (SHM) and wearable devices.

Advances in biomaterials and carbon nanostructures are enabling next-generation relative humidity (RH) sensors with broad applications. Here we report a gelatin-modified graphene ink (Ge-GTr), an eco-friendly formulation that delivers high-performance RH sensing when printed by aerosol jet. Devices fabricated with optimized 1.0Ge-GTr ink exhibited reliable operation across 10–90% RH at room temperature, with two distinct response regimes: 0.58% RH⁻¹ sensitivity at ≤ 60% RH (charge transfer/dielectric screening) and 2.5% RH⁻¹ at ≥ 60% RH (gelatin micelle swelling). The sensors achieved a peak response of 102% at 90% RH, resolution of ±2% RH, response time of ~75 s, and only 3% hysteresis between 30–70% RH. They also showed repeatable cycling behavior, robust temperature stability, and excellent mechanical flexibility. Demonstrations in breath analysis and food packaging confirmed their practical utility: the sensors distinguished breathing patterns of smokers and non-smokers and detected spoilage-related RH in meat packages, while maintaining high selectivity to RH over interfering gases. These results highlight Ge-GTr as a sustainable route to flexible, printed RH sensors for health monitoring and smart packaging applications.

The paper presents a comparative analysis of two types of flexible temperature sensors, made of carbon-based nanostructures composites. These sensors were fabricated by a low-cost screen-printing method, which qualifies them to large scale, portable consumer electronic products. Results of examined measurements show the possibility of application for thick film devices, especially dedicated to wearable electronics, also known as a textronics. Apart from general characterisation, the influence of technological processes on specific sensor parameters were examined, particulary the value of the temperature coefficient of resistance (TCR) and its stability during the device bending.

The article deals with the modeling of charged particles in a multicomponent plasma of electric arc discharge with binary collisions in the synthesis of carbon nanostructures (CNS). One of the common methods of obtaining the quality of fullerenes and nanotubes is arc synthesis under inert gas (helium). The determination of the necessary conditions and the mechanism of formation of carbon clusters in the plasma forming set CNS will more effectively and efficiently manage this process. Feature of the problem is that in a plasma arc discharge is a large number of particle interactions and on the cathode surface. Due to the high temperatures and high energy concentration in plasma detailed experimental investigation difficult to carry out. With the aim of avoiding difficult and costly physical experiments developed numerical methods for the analysis of plasma processes. In this article to solve a system of equations of Maxwell - Boltzmann basis for the authors had taken the method of large particles, which reduces the amount of computation and reduce the demands on computing resources. The authors cites the general design scheme of the large particles, and the algorithm of particle distribution of a multicomponent plasma in the phase plane at the initial time. In conclusion, the author argues that the results in the future will define the zone satisfies the energy conditions, the probability of formation of a plasma cluster groups of carbon involved in the synthesis of the CNS.

With the intensification of global aging trends and the continuous rise in the incidence of chronic diseases, the demand for health monitoring and early intervention has become increasingly urgent. Owing to their non-invasive nature, portability, and comfort, flexible wearable sensors have emerged as a key technology driving the development of personalized healthcare. Starting from specific application scenarios in health monitoring, this article systematically reviews recent research advances in flexible sensors within the healthcare field. Firstly, it outlines the design fundamentals of flexible sensors. This is followed by a focused analysis of their specific applications in monitoring vital signs, biochemical markers, as well as motion and neural activities, along with an in-depth exploration of the clinical significance, technical challenges, and targeted solutions in different scenarios. Finally, the current technical bottlenecks and clinical challenges are summarized, and an outlook on the future development of health monitoring systems is provided. This review aims to provide a systematic reference for the deep integration of flexible electronics technology and medicine.

A flexible and ultrasensitive interfacial iontronic multisensory sensor with an array of unique “cup-shaped” microcolumns for detecting pressure and temperature