Motion Monitoring Research Articles

Support-free printing origami-based 3D negative Poisson's ratio-structured piezoresistive sensor for motion monitoring

A convenient strategy for preparing meta-structures with a negative Poisson's ratio (NPR), which enhance mechanoelectrical responsiveness and are typically based on inner concave hollow cells, is 3D printing without support structures. However, this process requires the material to have high melt strength, often linked to high viscosity and low printability. In this work, we introduced 0D carbon black (CB) into a thermoplastic polyurethane (TPU)/1D carbon nanotubes (CNT) composite to create a dimension-hybrid filler system, enhancing strength with minimal viscosity increase. The results show that the bending modulus and Young's modulus of CB/CNT(1:3)/TPU composites are increased by 1.6 times and 1.8 times that of TPU, while its viscosity (2697.98 Pa⋅s) is lower than the allowed value of printer. Then, the 3D-printed suspension bridge of TPU is 42.7 % less saggy, significantly benefiting to preparing meta-structures. Based on a support-free 3D printable enclosed hollow structure, the TPU / CNT / CB composite material achieves an adjustable NPR between −0.59 and −0.20. Compared to unfolded structure, this NPR characteristic further improves the piezoelectric output voltage by 9.00 times, enhances the compressive modulus by 3.15 times, and improves the piezoresistive sensitivity by 122.0 %. Sensors based on this 3D-printed material showcase high performance stability and reproducibility, demonstrating their potential in wearable equipment.

Self-powered strain sensing devices with wireless transmission: DIW-printed conductive hydrogel electrodes featuring stretchable and self-healing properties

With rapid advancements in health and human–computer interaction, wearable electronic skins (e-skins) designed for application on the human body provide a platform for real-time detection of physiological signals. Wearable strain sensors, integral functional units within e-skins, can be integrated with Internet of Things (IoT) technology to broaden the applications for human body monitoring. A significant challenge lies in the reliance of most existing wearable strain sensors on rigid external power supplies, limiting their practical flexibility. In this study, we present an innovative strategy to fabricate glutaraldehyde (GA)-poly(vinyl alcohol) (PVA)/cellulose nanocrystals (CNC)/Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) conductive hydrogels through multiple hydrogen bonding systems. Combining the advantageous rheological properties of the precursor solution and the high specific surface area after freeze–thaw cycling, we have created a self-powered sensing system prepared by large-area printing using direct ink writing (DIW) printing. The resulting conductive hydrogel exhibits commendable mechanical properties (411 KPa), impressive stretchability (580 %), and robust self-healing capabilities (>98.3 %). The strain sensor, derived from the conductive hydrogel, demonstrates a gauge factor (GF) of 2.5 within a stretching range of 0–580 %. Additionally, the resultant supercapacitor displays a peak energy density of 0.131 mWh/cm3 at a power density of 3.6 mW/cm3. Benefiting from its elevated strain response and remarkable power density features, this self-powered strain sensing system enables the real-time monitoring of human joint motion. The incorporation of a 5G transmission module enhances its capabilities for remote data monitoring, thereby contributing to the progress of wireless tracking technologies for self-powered electronic skin.

Super-strain, high sensitivity, and multi-responsive flexible sensor based on nanocellulose hydrogels

The application of flexible sensors based on conductive hydrogels in human motion monitoring has been widely studied. Here, a facile one-pot method is proposed to prepare nanocellulose/polyacrylamide/sodium alginate hydrogel (CNWs/SA/PAM). The resulting CNWs/SA/PAM hydrogel has exceptional mechanical properties (7850 %, 1.3 MPa) and high sensitivity (14200 %, GF=3.6, 68 ms). The nanocellulose crystals (CNWs) are bent and entangled with the backbone of the polyacrylamide/sodium alginate (PAM/SA) hydrogel network, effectively transferring external mechanical forces to the entire physical and chemical cross-linking domains. This feature considerably improves the tensile strength, strain sensing range, and sensitivity of the hydrogel. The CNWs/SA/PAM hydrogel exhibits a sensitive response to water molecules and temperature-stimulated shape memory behaviour and can act as a programmable deformation actuator. The hydrogel sensor can detect and monitor subtle human motion signals in a timely and accurate manner. It is designed as a single-electrode friction nanogenerator insole (insole-TENG) that can monitor the large motion states of the human body in real time and can be efficiently used for small self-powered electronic devices. This study will shed some light on developing cellulose hydrogels in multifunctional human motion health detection sensors, soft-actuated robots, and self-powered applications for small electronic devices.

Facile strategy of Fe3+ rich collagen-based composite hydrogel for antibacterial, electricity harvesting and sensing applications

Conventional hydrogels have poor conductivity and low stretchability, limiting their practical applications for different purposes. Herein, collagen (CL) based, poly(vinyl alcohol) (PVA) and glutaraldehyde (GT) cross-linked ferric ion (Fe3+) rich highly conductive CL/GT/PVA/Fe hydrogel was developed. The presence of high CL, PVA and Fe3+ ions, together with the effective Fe3+ complexes formation, delivers the hydrogel with some particular assigns, such as high ionic conductivity (3.44 S.m−1) and antibacterial activity; furthermore, a very high stretchability. The CL/GT/PVA/Fe hydrogel demonstrated excellent mechanical properties, where the highest tensile strength of the hydrogels was ∼204.5 kPa at an elongation of 674 %, and the highest compressive strength was ∼0.39 MPa, with the highest stretchability of 81.67 %. The strengths are enhanced significantly by the incorporation of Fe3+ ions because of the formation of effective complexation of Fe3+ with rich hydroxyl and carboxyl groups of PVA and CL. As a flexible strain sensor, the CL/GT/PVA/Fe hydrogel with excellent conductivity manifests high sensitivity in human motion monitor. The hydrogels’ sufficient –OH and –COOH groups play a key role in imparting moist-induce electricity supply and the highest 173 mV of open circuit voltage (Voc) generated during moisture spray.

Design of self-healing nanocomposite hydrogels and the application to the detection of human exercise and ascorbic acid in sweat

Hydrogel sensors have broad application prospects in human motion monitoring and sweat composition detection. However, hydrogel-based sensors are faced with challenges such as low accuracy and poor mechanical properties of analytes detection. Based on mussel-inspired chemistry, we synthesized mesoporous silica@polydopamine-Au (MPS@PDA-Au) nanomaterials and designed a self-healing nanocomposite hydrogel to monitor human movement and ascorbic acid detection in sweat. Mesoporous silica (MPS) possess orderly mesoporous structure. Dopamine (DA) polymerized on the surface of MPS to generate polydopamine (PDA), forming the composite material MPS@PDA-Au. This composite was then embedded into polyvinyl alcohol (PVA) hydrogels through a simple freeze-thaw cycle process. The hydrogels have achieved excellent deformable ability (508.6%), self-healing property (90.5%) and mechanical strength (2.9 MPa). The PVA/MPS@PDA-Au hydrogel sensors had the characteristics of fast response time (123.2 ms), wide strain sensing range (0–500%), excellent fatigue resistance and stability in human detection. The detection range of ascorbic acid (AA) in sweat was wide (8.0 μmol/L-100.0 μmol/L) and the detection limit was low (3.3 μmol/L). Therefore, these hydrogel sensors have outstanding application prospects in human motion monitoring and sweat composition detection.

Ultrastretchable, Ultralow Hysteresis, High-Toughness Hydrogel Strain Sensor for Pressure Recognition with Deep Learning.

Hydrogel, as a promising material for a wide range of applications, has demonstrated considerable potential for use in flexible wearable devices and engineering technologies. However, simultaneously realizing the ultrastretchability, low hysteresis, and high toughness of hydrogels is still a great challenge. Here, we present a dual physically cross-linked polyacrylamide (PAM)/sodium hyaluronate (HA)/montmorillonite (MMT) hydrogel. The introduction of HA increases the degree of chain entanglement, and the addition of MMT acts as a stress dissipation center and cross-linking agent, resulting in a hydrogel with high toughness and low hysteretic properties. This hydrogel synthesized by a simple strategy exhibited ultrahigh stretchability (3165%), high breaking stress (228 kPa), high toughness (4.149 MJ/m3), and ultralow hysteresis (≈2% at 100% of strain). The fabricated hydrogel flexible strain sensors possessed fast response and recovery times (62.5:75 ms), a wide strain detection range (2000%), a strain detection limit of 1%, and excellent cycling stability over 500 cycles. Furthermore, the hydrogel flexible strain sensor can be used for human motion monitoring, gesture recognition, and pressure recognition assisted by deep learning algorithms, showing enormous promise for applications.

MXene/MWCNTs-based capacitive pressure sensors combine high sensitivity and wide detection range for human health and motion monitoring

Wearable pressure sensors with exceptional performance are playing a crucial role in various fields such as electronic skin, human motion monitoring, medical diagnosis, and human-computer interaction. However, achieving both high sensitivity and a wide sensing range with simple fabrication and low cost has proven to be a significant challenge for sensors. In this study, a simple capacitive pressure sensor is proposed that multi-walled carbon nanotubes (MWCNTs) are introduced into MXene (Ti3C2TX) as a ‘bridge’. Then the electrode which has excellent conductivity is obtained by filtration of MXene solution and MXene/MWCNTs solution at intervals. Additionally, green and degradable cellulose paper is used as the dielectric layer. The fabricated pressure sensor exhibits a high sensitivity of 4.7 kPa−1 for low pressure from 0 to 1 kPa, a wide detection range of 0–700 kPa, ultra-fast response and recovery times of 46 ms and 62 ms, respectively, and an extremely low detection limit of 0.32 Pa. The sensor remains stable even after 4500 cycles and can accurately monitor the movement of the human joints. Furthermore, it can track human physiological signals, which is beneficial for medical diagnosis and disease prevention, and has significant potential for application in the wearable technology field.

Rapid photo-crosslinking, highly conductive, and anti-freezing acrylamide-based hydrogels applied for ECG sensors

In recent years, ionic conductive hydrogels have attracted significant attention in the wearable sensors field due to their simplified preparation process, cost- effectiveness, and high conductivity. However, a large amount of water in traditional hydrogels inevitably condense into ice at low temperatures and make them lose various properties in their practical applications. Hence, this study proposes a method to rapidly synthesized a water/glycerol binary anti-freezing hydrogel only in 10 s through photo-initiated free-radical polymerization. The introduction of LiCl into the crosslinked network composed of acrylamide (AAm) and poly (ethylene glycol) diacrylate (PEGDA) regulated the ionic conductivity of the hydrogel. The hydrogel exhibits a fracture strain of 1062.1 %, a tensile strength of 31 kPa, and an adhesive strength of 6.49 kPa. The synergistic effects of glycerol and LiCl imparted excellent anti-freezing properties (−60 °C). The three-dimensional network structure of the hydrogel facilitates ion transport, exhibiting superior conductivity (30.25 S/m), maintaining high conductivity capability of 1.46 S/m even at a low temperature of −55 °C. Notably, the hydrogel demonstrates prolonged durability and stability in real-time human motion monitoring applications while concurrently exhibiting remarkable sensitivity as an ECG sensor. Hence, this as-prepared hydrogel can adapt to extreme environments and deliver comprehensive performance as an ECG sensor.

Recyclable and Stable Strain Sensors Based on Semi‐Wrapped Structure of Silver Nanowires in Polyvinyl Alcohol for Human Motion Monitoring

AbstractHighly sensitive strain sensors have been widely used in human motion monitoring, medical treatment, soft robots, and human–computer interaction, and the recycling of functional materials is in a huge demand for eco‐friendly and sustainable electronics. However, the manufacturing of recyclable strain sensors still remains challenging. Here, a semi‐wrapped structure based on silver nanowires and polyvinyl alcohol is proposed to realize a recyclable and stable strain sensor. It has shown excellent sensitivity, fast response, high stretchability and good environmental stability, and is successfully applied for human motion monitoring. In addition, a simple strategy is developed to effectively recycle silver nanowires in an eco‐friendly manner. The recyclable and stable strain sensor demonstrates potential applications in wearable and stretchable electronics, and the recycling strategy can be extended to other noble metal nanomaterials.

Carbon-based Wearable Pressure Sensor System for Real-time Step Frequency Monitoring

Abstract Wearable pressure sensors have attracted great attention in human motion and health monitoring due to their sensitivity, flexibility and portability that can provide continuous physiological information recording. However, current pressure sensors used for wearable motion monitoring suffer from low sensitivity, poor resistance to interference, and the inability to be mass-produced. In this study, we proposed the utilization of multi-walled carbon nanotubes (MWNTs) as sensing materials, fabric as substrates, and screen printing process for fabricating flexible pressure sensors. The fabricated sensors exhibited a high sensitivity at low pressure, and good stability of more than 3000 cycles. Moreover, we designed a wearable step frequency monitoring system for real-time recording of footstep frequency during human walking activities. The results demonstrated that the system accurately monitors frequency under different walking speeds and footstep activities during various movements, providing a promising strategy to develop wearable and wireless sensing system for real-time motion monitoring.

Flexible and wearable multilayer structure fiber sensor for motion and human physiological signal monitoring

AbstractThe development of flexible piezoresistive sensors has increasingly attracted widespread attention due to their various potential applications in wearable devices, human–machine interfaces, and health monitoring systems. Developing high‐performance sensors that can accurately monitor movement and human health monitoring is very necessary. This study uses silver nanoparticles, MXene, and polypyrrole to prepare conductive fabrics based on various fabrics through layer‐by‐layer encapsulation. Finally, conductive fabrics with different layers were encapsulated to prepare a multilayer fiber sensor. Next, the series piezoresistive performance of sensors made of different fabric materials and sensors with different layers were tested. The experimental results show that the sensor prepared has the best performance when the selected fabric material is mulberry silk and the number of layers of the fabric is five. After testing, the sensitivity of the sensor is 4.9029 at low strain and 0.7901 at high strain. Moreover, it exhibits good stability during 1600 compression‐release cycles and temperatures range from −20 to 60°C. The designed sensor performs well in motion and human physiological signal monitoring. This study provides new ideas and references for the design and research of multilayer fiber sensors.

Photoacoustic tracking of photo-magnetically powered nanoparticles for cancer therapy

Abstract The in vivo propulsion and monitoring of nanoparticles (NPs) have received tremendous achievements in the past decade. Developing functional NPs that can be efficiently manipulated inside the human body with a non-invasive tracking modality is critical to clinical translation. This study synthesized a photo-magnetically powered nanoparticle (PMN) with a Fe3O4 core and gold spiky surface. The Au-nanotips ensure PMNs have a strong light absorption in the second near-infrared (NIR) window and produce outstanding photoacoustic signals. The Bio-transmission electron microscopy and simulation results prove that the assembly of PMNs under a magnetic field further enhances the photothermal conversion in cells, contributing to the reduction of ambient viscosity. Photoacoustic imaging (PAI) realized real-time monitoring of PMN movements and revealed that laser plus magnetic coupling could improve intratumoral distribution and retention. The proposed methods exhibit excellent potential for the clinical research of cancer nanotherapies.

A tough, stretchable, adhesive and electroconductive polyacrylamide hydrogel sensor incorporated with sulfonated nanocellulose and carbon nanotubes

Recently, hydrogel sensors have been widely applied in wearable and portable electronics, but the low mechanical property, intolerance of fatigue, and low sensitivity and adhesion limit their further applications. In this study, sulfonated nanocellulose (SCNF) with dual functionality was blended into polyacrylamide (PAM) hydrogel matrix to reinforce the mechanical strength and facilitate the homogeneous dispersion of carbon nanotubes (CNTs). The SCNF-CNT/PAM hydrogel was designed through free radical polymerization to achieve commendable mechanical, electrical, and multifunctional properties. The environmental-friendly SCNF serves as bio-templates to facilitate the assembling of CNT into integrated SCNF-CNT structures with good dispersity, thus enabling the establishment of an integrated conducting and reinforcing network. The fabricated SCNF-CNT/PAM hydrogel exhibited outstanding compressive strength (∼0.45 MPa at 50 % strain), tensile strength (∼169.12 kPa), and antifatigue capacity under cyclic stretching and pressing. Furthermore, the multifunctional sensors assembled using this hydrogel demonstrated high strain sensitivity (gauge factor ~ 3.7 at 100–400 % strain) and effectively detected human motions. This design principle provides promising prospects for constructing next-generation multifunctional flexible sensors, and the integration of these distinctive properties enables the prepared composite hydrogels to find potential applications in various areas, such as implantable soft electronic devices, electronic skin, and human movement monitoring.

2443: Clarity based clinical safety margins for Prostate SBRT with intrafraction motion monitoring

2443: Clarity based clinical safety margins for Prostate SBRT with intrafraction motion monitoring

A hydrophobic phase-locking strategy enabling ultrarobust and water-stable self-healing elastomers for underwater ionotronics

Water-resistant conductive elastomers can endow soft electronic devices with reliable sensing performance for motion monitoring and real-time communication in aquatic environments. Nevertheless, traditional conductive elastomers typically suffer from notable shortcomings in terms of inferior mechanical robustness, weak stability, and self-healing capabilities in wet conditions and even underwater, significantly restricting their practical utility. Drawing inspiration from the optimization of multiphase structure, an ultrarobust underwater healable elastomer is constructed by incorporating biomass-derived long-chain segments with a large number of amide/benzene groups into a hierarchical H-bonding supramolecular network. The locking of multiple dynamic bonds by uniformly distributed hard-phase domains with dense hydrophobic barriers leads to the resultant elastomer gaining remarkably enhanced mechanical properties (stretchability, 2217.2 %; toughness, 272.97 MJ m−3) and outstanding capability to autonomously self-heal even underwater with a high ultimate strength over 10 MPa (aqueous healing for 24 h). Notably, it boasts exceptional healing stability to all types of harsh aqueous environments, such as strong acid/alkali, high temperature, and salty water. The application of the developed elastomer is also demonstrated by creating a multifunctional wearable sensor that can accurately detect and transmit information for a variety of human motions in both atmospheric and aquatic environments. The viable strategy reported herein for designing advanced multifunctional healable materials can be applicable for all-environment flexible iontronic devices.

2160: Sensitivity and imaging dose of two intrafraction prostate motion monitoring approaches

2160: Sensitivity and imaging dose of two intrafraction prostate motion monitoring approaches

Laser-Induced Graphene Strain Sensors for Body Movement Monitoring.

To enable the development of artificial intelligence of things, the improvement of the strain sensing mechanisms and optimization of the interconnections are needed. Direct laser writing to obtain laser-induced graphene (LIG) is being studied as a promising technique for producing wearable, lightweight, highly sensitive, and reliable strain sensors. These devices show a higher degree of flexibility and stretchability when transferred to an elastomeric substrate. In this article, we manufactured polydimethylsiloxane (PDMS)-encapsulated LIG piezoresistive strain sensors with a quasi-linear behavior and a gauge factor of 111. The produced LIG was morphologically characterized via Raman spectroscopy and scanning electron microscopy before and after the electromechanical characterization and before and after the LIG transfer to PDMS. The results from these analyses revealed that the integrity of the material after the test was not affected and that the LIG volume in contact with the substrate increased after transfer and encapsulation in PDMS, leading to the improvement of the sensor performance. The sensors' capability for measuring bend angles accurately was demonstrated experimentally, making them useable in a wide range of applications for human body movement monitoring as well as for structural health monitoring. Regarding body monitoring, a PDMS-encapsulated LIG sensor for knee bending angle detection was proposed. This device showed unaffected performance of 1500 cycles under 8% uniaxial deformation and with response times in the range of 1-2 s.

Self configuring mobile agent-based intrusion detection using hybrid optimized with Deep LSTM

Sensor nodes can be deployed in harsh or hostile environments in many applications, making these nodes more prone to failure. The illegal movement monitoring within the sensor networks is a most challenging problem. The mobile malicious nodes are preferred by the attacker to maximize his impact. For a dynamic environment, a promising technology of sensor networks is expected to Intrusion detection. Multi-mobile agents utilize many approaches, after verification that collects data from sensor nodes. However, these approaches are inefficient to verify all the sensor nodes (SNs) of the network, due to its high delay, energy consumption, and mobility. The proposed Dunnock Ibis optimization LSTM model (DIO opt LSTM) solves this problem. Here, the sensor nodes are grouped into clusters; hence, mobile agent performs verification only the cluster heads instead of verifying all the SNs. The proposed DIO optimization combines the unique behavior of Egret Swam and Ibis optimization algorithm which efficiently tunes the LSTM classifier, resulting in the model providing better convergence. The simulation results show the proposed system shows a better result than the existing system by utilizing the database IDS 2018 Intrusion CSVs, the analysis is done based on performance metrics such as End-end-delay (ED), normalized energy (NE), and throughput. At 200 nodes and 1500 rounds, the DIO opt LSTM method has efficiently performed 146 numbers of alive nodes, 0.46 ms of delay, 0.15 J of normalized energy, and 0.89 bps of throughput.

Polymer-assisted dispersion of reduced graphene oxide in electrospun polyvinylidene fluoride nanofibers for enhanced piezoelectric monitoring of human body movement

Electrospun graphene oxide (GO)/polyvinylidene difluoride (PVDF) and reduced graphene oxide (rGO)/PVDF piezoelectric hybrid nanofibers were prepared via electrospinning to enhance the β-phase content of the PVDF crystal structure. The addition of rGO increased the number of nucleation sites in the PVDF matrix, leading to an improved β-phase content in the nanofibers. Although the inclusion of GO also increased the β-phase content, rGO addition resulted in higher output voltages due to its greater conductivity compared to GO. rGO/PVDF produced higher output voltages than GO/PVDF because rGO has few oxygen-containing groups on its carbon atoms. The 1 wt% GO/PVDF nanofibers exhibited an 86.24 % β-phase content and an average output voltage of 3.2 V under a 15 N load. The 0.5 wt% rGO/PVDF nanofibers demonstrated an 84.09 % β-phase content and an average output voltage of 3.66 V under the same load. The nonionic surfactant Triton X-100 improved rGO dispersal, enhancing its effectiveness in inducing β-phase formation, and increasing the number of stress concentration points in the nanofibers. A piezoelectric device composed of TX-100/rGO/PVDF nanofibers exhibited stable performance even after 1,500 load cycles, generating an average output voltage of 7.13 V under a 15 N load. This device serves as both an energy harvester and a footwear sensor, offering potential applications in new sports monitoring technologies and self-powered wearables.

Recent Advances in Natural-Polymer-Based Hydrogels for Body Movement and Biomedical Monitoring.

In recent years, the interest in medical monitoring for human health has been rapidly increasing due to widespread concern. Hydrogels are widely used in medical monitoring and other fields due to their excellent mechanical properties, electrical conductivity and adhesion. However, some of the non-degradable materials in hydrogels may cause some environmental damage and resource waste. Therefore, organic renewable natural polymers with excellent properties of biocompatibility, biodegradability, low cost and non-toxicity are expected to serve as an alternative to those non-degradable materials, and also provide a broad application prospect for the development of natural-polymer-based hydrogels as flexible electronic devices. This paper reviews the progress of research on many different types of natural-polymer-based hydrogels such as proteins and polysaccharides. The applications of natural-polymer-based hydrogels in body movement detection and biomedical monitoring are then discussed. Finally, the present challenges and future prospects of natural polymer-based hydrogels are summarized.