Body Motion Sensor Research Articles

Alkyl-C60 liquid electrets as deformable mechanoelectric generators.

Special attention is being paid to the potential applicability of various soft electronics in deformable/wearable devices. These devices must be constantly connected to energy sources to ensure their uninterrupted operation. Electrets, which are capable of retaining quasi-permanent electric charges inside or on the surface of materials, are expected to be a battery-less power source. Here, we present a strategy for harvesting the charges in alkyl-C60 liquids. Suitable substitution of bulky yet flexible branched long-alkyl chains generated C60-mono-adducts and regioisomeric bis-adducts as room-temperature solvent-free liquids. These alkyl-C60 liquids were negatively poled by the corona-discharging and soaked in nylon fabric. The liquid of the C60 bis-adduct exhibited better charge retention in comparison to the liquid of the C60 mono-adduct. This suggests that the bulky long-alkyl chains provided proper insulation for the C60 core and charge trapping in the liquid. This charge-trapping behaviour and the inherent fluidity of the alkyl-C60 liquids enabled their fabrication into deformable mechanoelectric generator (MEG) devices. The MEG exhibited applicability as a deformable micropower source or vibration sensor by generating output voltage pulses even under folded/twisted/rolled conditions. The alkylated-liquid-based MEGs worked at frequencies similar to human body motion, showing promising potential for body motion sensors and healthcare applications.

Extraction of Lumbar Spine Motion Using a 3-IMU Wearable Cluster.

Spine movement is a daily activity that can indicate health status changes, including low back pain (LBP) problems. Repetitious and continuous movement on the spine and incorrect postures during daily functional activities may lead to the potential development and persistence of LBP problems. Therefore, monitoring of posture and movement is essential when designing LBP interventions. Typically, LBP diagnosis is facilitated by monitoring upper body posture and movement impairments, particularly during functional activities using body motion sensors. This study presents a fully wireless multi-sensor cluster system to monitor spine movements. The study suggests an attempt to develop a new method to monitor the lumbopelvic movements of interest selectively. In addition, the research employs a custom-designed robotic lumbar spine simulator to generate the ideal lumbopelvic posture and movements for reference sensor data. The mechanical motion templates provide an automated sensor pattern recognition mechanism for diagnosing the LBP.

Robust superhydrophobic wearable piezoelectric nanogenerators for self-powered body motion sensors

Self-powered wearable sensors have attracted extensive attention in tactile sensing, motion-detecting, and biomedical signal monitoring. The practical application of these devices, however, requires not only their high sensitivity, flexibility, and breathability, but also mechanical durability and long-term resistance to humidity, liquid, and bacteria. Herein, a robust superhydrophobic antibacterial self-powered piezoelectric nanogenerator (PENG) sensor is reported. The PENG sensor is comprised of flexible electrospun poly(vinylidene fluoride-co-trifluoroethylene) piezoelectric nanofiber membrane with spray-coated interdigitated carbon nanotube electrodes, which were subsequently encapsulated by a crosslinked conformal hydrophobic nanocoating wrapping around each individual fiber through initiated chemical vapor deposition (iCVD). The obtained sensor could accurately monitor various human behaviors such as breathing and different motions. The iCVD nanocoating provides excellent protection to the sensor, imparting self-cleaning, superhydrophobicity, and more than 90% anti-fouling rate against bacteria. As a result, the sensor shows reliable and durable sensing performance under harsh environments such as high humidity, chemical exposure, and mechanical impact. Finally, owing to its extraordinary long-term durability and stability, the PENG sensor was successfully integrated into shoe insoles to realize human gait monitoring.

A new 3D, microfluidic-oriented, multi-functional, and highly stretchable soft wearable sensor

Increasing demand for wearable devices has resulted in the development of soft sensors; however, an excellent soft sensor for measuring stretch, twist, and pressure simultaneously has not been proposed yet. This paper presents a novel, fully 3D, microfluidic-oriented, gel-based, and highly stretchable resistive soft sensor. The proposed sensor is multi-functional and could be used to measure stretch, twist, and pressure, which is the potential of using a fully 3D structure in the sensor. Unlike previous methods, in which almost all of them used EGaIn as the conductive material, in this case, we used a low-cost, safe (biocompatible), and ubiquitous conductive gel instead. To show the functionality of the proposed sensor, FEM simulations and a set of designed experiments were done, which show linear (99%), accurate (> 94.9%), and durable (tested for a whole of four hours) response of the proposed sensor. Then, the sensor was put through its paces on a female test subject’s knee, elbow, and wrist to show the potential application of the sensor as a body motion sensor. Also, a fully 3D active foot insole was developed, fabricated, and evaluated to evaluate the pressure functionality of the sensor. The result shows good discrimination and pressure measurement for different foot sole areas. The proposed sensor has the potential to be used in real-world applications like rehabilitation, wearable devices, soft robotics, smart clothing, gait analysis, AR/VR, etc.

Body Motion Sensor Analysis of Human-Induced Dynamic Load Factor (DLF) for Normal Walks on Slender Transparent Floors

Modern constructions are often characterized by the presence of slender and aesthetically fascinating components and assemblies. For pedestrian systems in particular, such constructions are notoriously associated with possible vibration issues, and thus require special calculations. When these slender systems are made of structural glass, additional effects due to transparency may also affect human behaviours and motions. In this paper, based on a single body motion, a microelectromechanical system (MEMS) sensor in the body’s centre of mass (CoM) is introduced, an extended, original experimental investigation is presented, and human-induced effects on slender transparent floors are discussed. Major attention is given to the well-known dynamic load factor (DLF) induced by a single pedestrian’s normal walk; a fixed walking rate is assigned, and different substructures (with major variations in their structural dynamic parameters) are taken into account. A discussion of experimental results is proposed for rigid reinforced concrete (RC), and a laboratory contrast system (SLAB#1), which is used as a reference for the analysis of DLF trends on relatively light and flexible transparent glass flooring systems (SLAB#2 and SLAB#3). It is shown that structural frequency and mass, but also possibly transparency, can affect human motion and result in a quantitative modification of measured DLF values, especially for the first and second harmonics of vertical force components.

An ultralight, flexible, and biocompatible all-fiber motion sensor for artificial intelligence wearable electronics

New-generation human body motion sensors for wearable electronics and intelligent medicine are required to comply with stringent requirements in terms of ultralight weight, flexibility, stability, biocompatibility, and extreme precision. However, conventional sensors are hard to fulfill all these criteria due to their rigid structure, high-density sensing materials used as the constituents, as well as hermetical and compact assembly strategy. Here, we report an ultralight sensing material based on radial anisotropic porous silver fiber (RAPSF), which has been manufactured by phase separation and temperature-controlled grain growth strategy on a modified blow-spinning system. The resistance of RAPSF could be dynamically adjusted depending on the deflected shape. Furthermore, an all-fiber motion sensor (AFMS) with an ultra-low density of 68.70 mg cm−3 and an overall weigh of 7.95 mg was fabricated via layer-by-layer assembly. The sensor exhibited outstanding flexibility, breathability, biocompatibility, and remarkable body motion recognition ability. Moreover, the AFMS was shown to have great potential as an artificial intelligence throat sensor for throat state identification at the accuracy above 85%, allowing one to spot the early onset of the viral throat illness.

Accelerometer-based analyses of animal sleep patterns

Body-motion sensors can be used to study non-invasively how animals sleep in the wild, opening up exciting opportunities for comparative analyses across species.

Nanofiber-Based Substrate for a Triboelectric Nanogenerator: High-Performance Flexible Energy Fiber Mats.

Flexible and stretchable triboelectric nanogenerators (TENGs) are the next-generation systems for wearable and portable electronics. In this study, we have demonstrated an all nanofiber-based TENG for energy harvesting and biomechanical sensing applications. The TENG was prepared using the Forcespinning (FS) method to produce poly(vinylidene fluoride) (PVDF) and thermoplastic polyurethane (TPU) nanofiber (NF) membranes. The TPU nanofiber membranes were interfaced with a homogeneously sputtered gold nanofilm. The experimental characterization of the PVDF-TPU/Au NF-TENG revealed that surface interfaced with dispersed gold in a TPU fiber membrane produced a maximum open-circuit voltage of 254 V and a short-circuit current of 86 μA output at a 240 bpm load frequency, which was, respectively, 112 and 87% greater than bare PVDF-TPU NF-based TENG. All systems were composed of an active contact surface area of 3.2 × 2.5 cm2. Furthermore, the TENG was able to light up 75 LEDs (1.5 V of each) by the hand-tapping motion. The resistive load and capacitor test results exemplified a TENG offering a simple and high-performance self-chargeable device. Furthermore, we have tested the TENG's response for biomechanical movements at different frequencies, suggesting the TENG's potential to be also used as a cost-effective self-powered flexible body motion sensor.

Boosting piezoelectric and triboelectric effects of PVDF nanofiber through carbon-coated piezoelectric nanoparticles for highly sensitive wearable sensors

Piezoelectric and triboelectric effects are vital mechanisms in motion sensing. Improving both the piezoelectric performance and triboelectric effect for a single material is an important approach to further improve the sensitivity of the sensor. Herein, we achieve the enhancement of both effects in electrospun polyvinylidene fluoride (PVDF) nanofiber by simply adding carbon-coated zinc oxide (ZnO@C) nanoparticles as additive. We found that ZnO@C can not only increase the β-phase in PVDF, resulting in an enhanced piezoelectric coefficient. It also negatively shifted the surface potential of PVDF to a high value of −740 mV, thereby modifying the triboelectric effect. The fabricated ZnO@C/PVDF nanogenerator exhibits 4 times enhancement in the voltage output, thus resulting in high sensitivity of 0.98 V kPa−1 when used as wearable sensors. Due to the good mechanical properties of nanofibers, we also demonstrated the application of ZnO@C/PVDF nanogenerator as body motion sensor with excellent deformation stability. Therefore, adding carbon-coated piezoelectric nanoparticles provides an effective approach to simultaneously enhance the piezoelectric and triboelectric effects of ferroelectric polymer for highly sensitive wearable sensors.

Stimuli-Responsive Electrospun Piezoelectric Mats of Ethylene-co-vinyl Acetate-Millable Polyurethane-Nanohydroxyapatite Composites.

Piezoelectric materials have gained interest among materials scientists as body motion sensors and energy harvesters on account of their fast responsiveness and substantial output signals. In this work, piezoelectric polymer mats have been fabricated from ethylene-co-vinyl acetate-millable polyurethane/nanohydroxyapatite (EVA-MPU/nHA) composite systems by employing the electrospinning technique. The ferro-piezoelectric features of the samples were confirmed from the butterfly loops of electrostatic force microscopy (EFM) amplitude signals as well as through the hysteresis curves of the EFM phase recorded with the assistance of dynamic-contact EFM. Piezoelectric responses of the samples to random finger tapping were evaluated after fabricating a simple device prototype connected to an oscilloscope. The efficacy of the mats to generate a voltage in response to activities such as mechanical bending, movement of throat muscles while drinking, movement of elbow joints, air blowing, and so forth has also been investigated. The results suggest the promising possibility of fabricating user-friendly piezoelectric mats out of the EVA-MPU/nHA system for physiological motion-sensing applications.

Predicting multimodal presentation skills based on instance weighting domain adaptation

Presentation skills assessment is one of the central challenges of multimodal modeling. Presentation skills are composed of verbal and nonverbal skill components, but because people demonstrate their presentation skills in a variety of manners, the observed multimodal features vary widely. Due to the differences in features, when test data samples are generated on different training data sample distributions, in many cases, the prediction accuracy of the skills degrades. In machine learning theory, this problem in which training (source) data are biased is known as instance selection bias or covariate shift. To solve this problem, this paper presents an instance weighting adaptation method that is applied to estimate the presentation skills of each participant from multimodal (verbal and nonverbal) features. For this purpose, we collect a novel multimodal presentation dataset that includes audio signal data, body motion sensor data, and text data of the speech content for participants observed in 58 presentation sessions. The dataset also includes both verbal and nonverbal presentation skills, which are assessed by two external experts from a human resources department. We extract multimodal features, such as spoken utterances, acoustic features, and the amount of body motion, to estimate the presentation skills. We propose two approaches, early fusing and late fusing, for the regression models based on multimodal instance weighting adaptation. The experimental results show that the early fusing regression model with instance weighting adaptation achieved $$\rho =0.39$$ for the Pearson correlation, which presents the regression accuracy for the clarity of presentation goal elements. In the maximum case, the accuracy (correlation coefficient) is improved from $$-0.34$$ to +0.35 by instance weighting adaptation.

0.8BNT–0.2BKT ferroelectric-based multimode energy harvester for self-powered body motion sensors

Abstract Exploring the various modes of forces such as tensile, bending along with regular compressive force stimulation is required to achieve superior applications from piezoelectric nanogenerators (PENG). The synthesized 1-x(Bi0.5Na0.5TiO3)-x(Bi0.5K0.5TiO3) (BNKT) structural analysis revealed the formation of a morphotropic phase boundary (MPB) at x = 0.2. The MPB 0.8BNT–0.2BKT system exhibited a dielectric constant of 1338 at 1 kHz, a remanent polarization (Pr) of 37.14 μC/cm2 with a coercive field (Ec) of 28.8 kV/cm at 1 Hz, and a piezoelectric coefficient (d33) of 110 pC/N. Composite films based on BNKT82 were then used to prepare stretchable, planar, and compressive PENGs. The stretchable PENG (SPENG) generated 8.1 V and 80 nA. The planar PENG (PPENG) in bending mode yielded 12.5 V and 110 nA, while the same device in compressive mode delivered 22.5 V and 210 nA with a power density of 13.81 mW/m2 at 90 MΩ. The PENGs analyzed under poled, unpoled, displacement, and acceleration effects systematically; also inspected stability, capacitor charging tests. The PENGs are demonstrated as self-powered human body sensors under the multimode of forces generated by the human body's movement.

High-performance stretchable PZT particles/Cu@Ag branch nanofibers composite piezoelectric nanogenerator for self-powered body motion monitoring

The development of stretchable nanogenerators has attracted intensive attentions for their promising applications in wearable electronics recently. Here, a newly high-performance stretchable PZT particles/Cu@Ag branch nanofibers (BNFs) nanocomposite piezoelectric generator (NCPG) is reported. The uniform mixture of PZT particles and Cu@Ag BNFs is blended into silicone rubber matrix that exhibits remarkably piezoelectric, mechanical and electrical characteristics. Owing to the similar molding method and the identical elastic matrix, the piezoelectric layer and the electrode layers could be completely integrated into stretchable NCPG based on all-in-one structure, which reveals high output performances (Vpeak–peak ≈ 61 V, Ipeak–peak ≈ 1.1 μA, 22.36 μw cm−3). The generated electricity is utilized to directly light five green emitting diodes (LEDs) and to drive a digital thermometer after stored in capacitor under the mechanical tensile strain stimulation. Moreover, the stretchable NCPG could act as a self-powered body motion sensor for distinguishing the bending angles and frequencies of the knee joint. This work provides a novel design idea for stretchable nanogenerators and shows great potential applications in artificial intelligence, medical diagnosis and movement entertainment.

Sensing body motions based on charges generated on the body

The sensing of body motions is of great importance in areas such as healthcare, rehabilitation, and human-computer interactions. Different methods have been developed based on visual or electrical signals. However, such signals are acquired by external devices and are not intrinsic signals that are created on the body. Here, we report a new universal body motion sensor (UBS) to detect motions based on the intrinsic contact electrification (CE) of the skin or electrical induction (EI) of the body. The CE or EI generates charges on the body, leading to potential differences between the body and ground that can be measured to identify different body motions, such as motions of the head, arms, fingers, waist, legs, feet and toes. Proof-of-concept experiments have demonstrated that the UBS can be used to monitor the conditions of people with Parkinson's disease (PD) and to quantitatively monitor the recovery of those with a leg injury, suggesting great potential for healthcare applications.

Highly transparent triboelectric nanogenerator utilizing in-situ chemically welded silver nanowire network as electrode for mechanical energy harvesting and body motion monitoring

Triboelectric nanogenerators (TENGs) functioning as energy harvester as well as body motion sensor pose great significance for oncoming wearable (opto)electronic systems. Herein, A transparent welded AgNW electrode based TENG (WA-TENG) is demonstrated. AgNWs are in-situ chemically welded with surfacial silver oxide naturally formed in air as solder and hydrazine as reductant based on epitaxial recrystallization, ensuring high transparency and conductivity of the electrode used in TENG. This welding endows AgNW electrodes with a high transmittance of 96% (at 77 Ω/sq sheet resistance) and low sheet resistance of 18 Ω/sq (at 92% transmittance), meanwhile, can effectively heal the damaged AgNW network. The WA-TENG exhibits a transmittance up to 95%, and generates an open-circuit voltage (Voc) of 66 V, short-circuit current (Isc) of 8.6 μA, and peak power density of 446 mW/m2 under single-electrode mode at 2 Hz. Besides, it can be employed to monitor human body motions, including bending of the elbow, eye blinking, and bending angle and frequency of the finger. Lastly, the WA-TENG serves as a tactile sensor to record touch control of a smart phone by the finger. The WA-TENG with standout transparency, electric output and sensing performance underscores the crucial role in self-powered wearable multifunctional devices.

Human–Machine Interfacing Enabled by Triboelectric Nanogenerators and Tribotronics

AbstractWith the advances of artificial intelligence (AI), autonomous robotics, virtual reality (VR) and Internet of things (IoT), an intelligent and ubiquitous human–machine interfacing (HMI) ecosystem has become a desire and attracted lots of interests. Triboelectric nanogenerators (TENG), as a natural and effective mechanical‐to‐electrical signal conversion technology, have been successfully utilized to realize many types of HMI, including smart keyboards, body motion sensors, the electronic skin, voice sensors, the triboelectrification‐induced electroluminescence, and the artificial muscle. Meanwhile, tribotronics, as the coupling field of TENG and semiconductors, has demonstrated the feasibility for tactile switch or sensing with the possibilities of high integration and large scale. The fundamental theory of TENG and tribotronics is revisited herein. In addition, the definition of HMI and, for the first time, the research progress of the TENG and tribotronics enabled HMI are systematically and thoroughly reviewed. Finally, the perspectives in this emerging field are also discussed.

Can Virtual Reality, Interactive Game, and Body Motion Sensors be a Replacement for General Anesthesia in Children Receiving Radiation Therapy?

To keep some young patients still during the daily radiation treatment (XRT) requires general anesthesia, which is expensive, time demanding, and has short and long-term consequences to these young patients. This study investigate a noninvasive technique using virtual reality (VR), interactive game, and body motion sensors to keep young patients to remain still during XRT, in place of general anesthesia. The proposed VR system consists of: (1) Head Mounted Display (HMD) that can display 3-D 1080p video and audio; (2) Multiple wireless motion sensors attached to body, arms and legs; (3) multi-level 3-D games(4) the computer system that incorporates all these components and provide output to patients and technicians. The Bluetooth motion sensors have 6 degree of freedom and provide instantaneous motion signal (rotation and translation) and are integrated into the game play. The game component will feature patient as an avatar flying an aero-skateboard to help mother dinosaur to collect all the lost eggs through multiple terrains (game levels) of forest, desert, mountain, etc. Positive feedback given as scores and bonus throughout the process to stimulate the patient during the 30-45 minute duration of the treatment. Once the patient is set in the reference position (, i.e., simulation position) and the game starts, as long as the patient remains still, the avatar will fly and collect eggs with different colors and adding scores. If motion of any body parts is detected above certain set threshold, the avatar is stopped, and warning is given to patients and therapist computer console indicating which part of needed to be still or resume to reference position. Once this is done, the game resumes. The therapist can hear and see what patients see, and there are two-way communication between patients and therapist. At the end of the session, depending on the score, the patient will be rewarded with toys. A prototype has been developed and has been tested in 15 healthy young children from age 4 to 10. After a few attempts, all children can comprehend and remain still for at least 30 min. Some adjustments in the gameplay and additional game levels were made to keep patients engaged. The proposed VR system can potentially offer an alternative to general anesthesia in some children undergoing XRT. This can significantly reduce morbidity, cost, and inefficiency in the radiation treatment of pediatric population. The next step is to perform a pilot clinical study on actual pediatric patients undergoing radiation treatments.

A Novel System for Deep Inspiration Breath Hold (DIBH) using Virtual Reality, Head-Mounted Device, 3-D Game, Camera and Wireless Body Motion Sensor

A Novel System for Deep Inspiration Breath Hold (DIBH) using Virtual Reality, Head-Mounted Device, 3-D Game, Camera and Wireless Body Motion Sensor

Block Copolymer Elastomer with Graphite Filler: Effect of Processing Conditions and Silane Coupling Agent on the Composite Properties.

The control of morphology and interface in poly(styrene-ethylene/butylene-styrene) (SEBS) composites with graphitic fillers is extremely important for the design of piezoresistive sensors for body motion or flexible temperature sensors. The effects of a high amount of graphite (G) and silane coupling agent on the morphology and properties of SEBS composites with anisotropic mechanical properties are reported. The physical and chemical bonding of silane to both G and SEBS surface was proved by EDX and TGA results; this improved interface influenced both the thermal and mechanical properties of the composite. The vinyltriethoxysilane (VS) promoted the formation of char residue and, being tightly bound to both SEBS and G, did not show separate decomposition peak in the TGA curve of composites. The mechanical properties were measured on two perpendicular directions and were improved by both the addition of VS and the increased amount of G; however, the increase of storage modulus due to orientation (from 5 to 15 times depending on the composition and direction of the test) was more important than that provided by the increase of G concentration, which was a maximum of four times that obtained for 15 wt % graphite. A mechanism to explain the influence of G content and treatment on the variation of storage modulus and tan δ depending on the direction of the test was also proposed.

Wearable Wide-Range Strain Sensors Based on Ionic Liquids and Monitoring of Human Activities.

Wearable sensors for detection of human activities have encouraged the development of highly elastic sensors. In particular, to capture subtle and large-scale body motion, stretchable and wide-range strain sensors are highly desired, but still a challenge. Herein, a highly stretchable and transparent stain sensor based on ionic liquids and elastic polymer has been developed. The as-obtained sensor exhibits impressive stretchability with wide-range strain (from 0.1% to 400%), good bending properties and high sensitivity, whose gauge factor can reach 7.9. Importantly, the sensors show excellent biological compatibility and succeed in monitoring the diverse human activities ranging from the complex large-scale multidimensional motions to subtle signals, including wrist, finger and elbow joint bending, finger touch, breath, speech, swallow behavior and pulse wave.