Flexible Bending Sensor Research Articles

Adaptive pneumatic soft gripper with embedded flexible bending sensor

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.

Novel Bending Sensor Based on a Solution-Processed Cu2O Film with High Resolution Covering a Wide Curvature Range.

A Cu2O film is prepared on a flexible polyethylene terephthalate substrate for a bending sensor using the spin–spray method, a facile and low-environmental-load solution process. The Cu2O bending sensor shows high sensitivity and high resolution not only over a wide range of curvatures (0 < κ < 0.21 mm–1) but also for very small curvature changes (Δκ = ∼ 0.03 mm–1). The bending response of the sensor exhibited a curvature change of high linearity with a good gauge factor (18.2) owing to the grain-boundary resistance and piezoresistive effects of the fabricated Cu2O film. In addition, the sensor possesses good repeatability, stability, and long-term (>30 days) and mechanical fatigue durability (1000 bending–release cycles). The sensor is capable of detailed monitoring of large- and small-scale human motions, such as finger bending, wrist bending, nodding, mouth opening/closing, and swallowing. In addition, excellent stability and repeatability of the monitoring performance is observed over a wide range of motion angles and speeds. All of these results demonstrate the potential of the flexible bending sensor based on the Cu2O film as a candidate for healthcare monitoring and wearable electronics.

Enhanced Piezoelectric Performance of Various Electrospun PVDF Nanofibers and Related Self-Powered Device Applications.

The piezoelectric polymer poly(vinylidene fluoride) (PVDF) has been widely employed for energy harvesting or sensors. Its piezoelectricity originates from the unique crystal structure and the oriented electric dipoles. Generally, electrospinning (ES) is able to improve the crystallinity and piezoelectricity of PVDF. In this investigation, three types of ES, including far-field ES with random (R-PVDF-FFES) or aligned distribution (A-PVDF-FFES) and near-field ES (PVDF-NFES), are applied to fabricate a one-step polarized PVDF membrane. To compare the piezoelectricity of separated PVDF-NFES fibers, the array of PVDF-NFES fibers is encapsulated in polylactic acid (PLA). The result shows that the piezoelectricity of PVDF is dramatically enhanced by NFES and FFES. In d31 mode, the current density of PVDF-NFES-PLA is 75.63 pA cm-2 with a 2 Hz shear force, which is four times larger than A-PVDF-FFES (17.62 pA cm-2) or seven times larger than R-PVDF-FFES (10.63 pA cm-2). Due to its outstanding property, the PVDF-NFES-PLA membrane is designed to be applied as a self-powered device. The unimorph cantilevers are prepared to harvest the vibration energy and their output power density reaches 95.3 μW m-2 at a resonance frequency of 31 Hz. Meanwhile, the flexible bending sensor and pressure sensor are fabricated with a PVDF-NFES-PLA membrane, which shows the stable response for pressure with sensitivity values of 864.68 and 22.6 mV kPa-1, respectively.

An Approach to Design a Wireless Air Flow Transmitter Using Flex Sensor

In process industries, air flow rate measurement and transmission are usually performed by various passive conventional sensors. Here, air flow rate for moderate flow applications is sensed by resistive type flexible bend sensor having the characteristics of light weight, tiny size, cost-effective, fine linearity and also good repeatability. The flexible resistive type bends sensor which acts as a cantilever beam derives the linear relationship between air flow rate and the change in resistance of the sensor in the form of an electrical signal. For transmission purposes, the generated electrical signal passes through the electrical communication system which is not permeable in hazardous and inflammable areas of the process industry. Henceforth, for the data transmission purpose, Internet of Things (IoT) is being introduced in industries for avoiding explosions due to electric spark and also the real-time data is transmitted throughout the globe with the help of internet. The proposed air flow transmitter has been theoretically analyzed in this paper and the relationship of air flow rate with a transmitted voltage signal has been derived. The experiment has been performed on the fabricated prototype air flow measuring unit. The experimental results are presented in the paper which is matched with the theoretical one. The proposed IoT based air flow transmitter unit shows linear characteristic with good repeatability. The higher value of air or any clean fluid flow rate can be measured by this prototype flow transmitter by only changing the dimensions of the cantilever type bend sensor.

IMU sensor-based data glove for finger joint measurement

&lt;p&gt;The methods used to quantify finger range of motion significantly influence how hand disability is reported. To date, the accuracy of sensors being utilized in data gloves from the literature has been ascertained yet need further analysis. This paper presents an inertial measurement unit sensor-based data glove for finger joint measurement developed for collecting a range of motion data of distal interphalangeal, proximal interphalangeal and metacarpophalangeal finger joints of an index finger. In this study, three inertial measurement sensors, MPU-6050 and two flexible bend sensors which are capable to detect angle displacement were attached to the distal interphalangeal, proximal interphalangeal and metacarpophalangeal finger joint points on the glove. The data taken from inertial measurement unit sensors and flexible bend sensors were acquired using Arduino and MATLAB software interface. The data obtained were compared with the reference data measured from goniometer to allow for accurate comparative measurement. The percentage of error resulted from MPU-6050 sensor unit were ranged from 0.81 % to 5.41 % were very low which indicates high accuracy when compared with the measurements obtained using goniometer. On the other hand, flexible bend sensor shows low accuracy (11.11 % to 19.35 % error). In conclusion, the inertial measurement unit sensor-based data glove using MPU-6050 sensors can be a reliable solution for tracking the progress of finger rehabilitation exercises. In order to motivate patients to adhere to the therapy exercises, interactive rehabilitation game will be developed in the future incorporating MPU-6050 sensors on all five fingers.&lt;/p&gt;

Design an Interfacing Tracking System in Rehabilitation Therapies Between The Elbow Joint of The Human Arm and The Prosthetic Arm

Myoelectric prostheses have seen an increased application in clinical practice and research, due to their potential for good functionality and versatility. Yet, myoelectric prostheses still suffer from a lack of intuitive control and haptic feedback, which can frustrate users and lead to abandonment. To address this problem, a prosthetic arm was designed to help the amputees, who unfortunately lost their upper limb. Then, the prosthetic arm was equipped with a hybrid haptic feedback stimulation system to compensate for the missing sensation and enable the amputees to easily perform their normal life activities. The tracking system between the elbow joints of the human and the prosthetic arms was required to accomplish the experimental tests with the able-body subjects. Accordingly, this study is a platform for the main project. The major problem is to synchronize the movements of the prosthetic arm’s elbow joint with the human arm’s elbow joint within a high response, acceptable accuracy, and low error. Therefore, the PID controller was used to control the tracking system and the flexible bending sensor was attached to the volunteer’s elbow joint to record its rotational movements. The results verified the functionality of the proposed tracking system to synchronize the joints movements and enable the prosthetic arm to follow the movements of the volunteer’s arm within 0.062 sec. Finally, the effectiveness of the proposed elbow joints tracking system to synchronize the motions of the volunteer and he prosthetic arms was concluded.

Design of an Ultrasensitive Flexible Bend Sensor Using a Silver-Doped Oriented Poly(vinylidene fluoride) Nanofiber Web for Respiratory Monitoring.

We propose a design strategy to fabricate a flexible bend sensor (BS) with ultrasensitivity toward airflow using all-poly(vinylidene fluoride) (PVDF) nanofiber web-based sensing elements and electrodes to monitor human respiration. The unique electrospinning (rotational speed of collector of 2000 rpm and tip-to-collector distance of 4 cm) with silver nanoparticle interfacing was introduced to prepare a Ag-doped oriented PVDF nanofiber web with high β-phase content as a sensing element (AgOriPVDF, β-phase crystallinity ∼44.5%). After that, a portion of the prepared AgOriPVDF was processed into a flexible and electrically conductive electrode through an electroless silver plating technique (SP-AgOriPVDF). Interestingly, the encapsulated AgOriPVDF BS with the SP-AgOriPVDF electrode exhibited superior piezoelectric bending response (open-circuit peak-to-peak output voltage, Vp-p ≈ 4.6 V) to injected airflow, which is more than 200 times higher than that of the unpackaged randomly aligned PVDF nanofiber web BS with a conductive tape electrode (Vp-p ≈ 0.02 V). In addition, the factors influencing the bend sensitivity of the BS such as the β-phase content, nanofiber orientation, flexibility of the electrode, and so forth were thoroughly analyzed and then discussed. We also demonstrated that the AgOriPVDF BS has sufficient capability to detect and identify various respiratory signals, presenting a great potential for wearable applications, for example, smart respiratory protective equipment.

Soft hand perception based on embedded optical fiber bending sensor

The perception capability of soft humanoid hand is very important to the implementation of friendly interactive and dexterous operation. The flexible optical bending sensor which is easy to be embedded into the soft finger is comprised of light emitting diode (LED), optical fiber and photo-sensitive sensor. The roughened optical fibers can generate light overflow. And the bend degree of soft fingers can be obtained by detecting the loss of light energy. The abilities of continuous movement detection, action gestures and object size recognition are implemented according to the following operations: ① calibrating the initial (unbent) and maximum bending statuses of soft fingers with normalization method; ② segmenting the normalized data by uniform, nonuniform and hysteresis segment method; ③ merging together the information of five fingers. The experiment results show that the proposed optical fiber bending sensor is able to detect the continuous sinusoidal movement status, correctly recognize various gestures and grasping postures and the object size. Combining hysteresis subsection method, the shortcoming of single point subsection oscillating near subsection point is overcome, and the recognition rate is improved. This optical flexible bending sensor has the advantages of electromagnetic immunity and easy to be embedded. It has important application value in soft robotic hand or soft actuator.

When Stretchable Sensing Meet Flexible Robotics

Advantages of soft, flexible materials with developments in stretchable electronics can be intertwined for a promising sensorized flexible robotics platform to work on a resilient, adaptable manipulator aimed to meet ever-increasing demands in safe regulated medical environments. Taking advantages of these soft magnetic polymers, we propose a novel, soft-squishy and flexible bend sensor by determining the relationship between inductance changes with bending angle. This bend sensor employs flexible wire embedded in a silicone elastomer with the different permeable core. The principle notion is to have a comprehensive analysis of the change in morphology of the sensor with bending angle which can be translated to inductance generated therein. The performance of the sensor is evaluated with various experimental trials while analytical modeling elucidates that the bend angle is linearly proportional to the sensor signal citing R-square value up to 0.9204. The proposed sensor produces the desired output in the electromagnetic frequency range of 8-10 MHz with a tunable sensitivity of 0.418 mV/rad. The sensor is robust enough to stretch up to twice of its original length. The main advantage of this bend sensor is its simple fabrication technique, flexibility, robustness, and economical. Conclusively, this induction based tactile bending sensor is proved to produce robust output and can be extrapolated to sense bending angle using induction principle for the rehabilitative device, wearable robots, and related biomedical applications requiring low cost, soft and flexible operations. To equip robotic manipulators with intelligence, tactile sensors are extensively used for detecting various external stimuli like slippage, grasping force and imitate the tactile perceptions. Since past few decades, there have been various researches in realising sensing element on a soft surface to obtain stretchable, foldable and flexible sensors. Apart from these external stimuli measurements, various bend sensors were developed to determine the curvature of bending and utilized in different applications like measurements of flexion and extension of body joints. These bend sensors were realised on different hardware and software technology namely optical fibre bend sensor, resistive and capacitive-based sensor. For small size, increased MEMS sensors were developed. Resistive based sensors consist of pressure sensitive element which changes its resistance based on force or induced deformation. The sensitive element is usually comprised of conductive ink, rubber or elastomer. These sensors are affordable and commercially available in the market with a higher spatial resolution that employs fewer electronics which makes signal processing easier to work in mesh configurations. Apart from these above-mentioned technologies, inductive based tactile sensors are based on the principle of magnetic coupling. Modulating the inductance of the coil by varying the length and the permeable core, in turn, modulates the sensing voltage. The sensors based on this technology are still under development and not widely explored like others. Although they do not fix all the disadvantages of the above-mentioned technologies, they have a high dynamic range, linear output and can be employed at a higher frequency. This makes the construction bulky and incurs higher losses. Therefore, we aimed to develop a sensor with only one coil that acts as both primary and secondary/sensing coil. Specifically, we propose a novel soft inductive Solenoidal Bend Sensor (SBS) completely different from the existing technology. This sensor comprises of a flexible coil with a protective covering made of elastic material. This silicone elastomer provides mechanical compliance and robustness to the sensor. Due to SBS flexible yet resilient properties, this has promising applications in the field of wearable electronics, soft robotics, drug delivery, medical implants, human-machine interaction. In this paper, the geometry of the sensor is considered like a single cantilever beam hung through certain height and bent with tangential and normal force. Thus, the characterization and mathematical modelling of the sensor is simpler due to the simpler geometrical structure. This developed sensor uses a passive L–R circuitry that consists of a fixed resistor and a variable inductor. The variable inductor is coupled with elastomer element that makes dimensional changes in response to the target parameter to modify the inductance. The material and the design of the sensor is economical, readily available and does not require complex fabrication procedure. SBS can be modified by varying the wire gauge length. This novel SBS is sensitive to bidirectional force and can be calibrated in near terms for the measurement of the angle or the force in the finger joints for rehabilitation.

Electromagnetically Enhanced Soft and Flexible Bend Sensor: A Quantitative Analysis With Different Cores

Advantages of soft, flexible materials with developments in refined magnetic actuation can be intertwined for a promising platform to work on a resilient, adaptable manipulator aimed to meet ever-increasing demands in safe regulated medical environments. Taking advantages of these soft magnetic polymers, we propose a novel, soft-squishy and flexible bend sensor by determining the relationship between inductance changes with bending angle. This bend sensor employs flexible wire embedded in a silicone elastomer with the different permeable core. The principle notion is to have a comprehensive analysis of the change in morphology of the sensor with bending angle which can be translated to inductance generated therein. The performance of the sensor is evaluated with various experimental trials while analytical modeling elucidates that the bend angle is linearly proportional to the sensor signal citing R-square value up to 0.9204. The proposed sensor produces the desired output in the electromagnetic frequency range of 8–10 MHz with a tunable sensitivity of 0.418 mV/rad. The sensor is robust enough to stretch up to twice of its original length. The main advantage of this bend sensor is its simple fabrication technique, flexibility, robustness, and economical. Conclusively, this paper on induction based tactile bending sensor is proved to produce robust output and can be extrapolated to sense bending angle using induction principle for the rehabilitative device, wearable robots, and related biomedical applications requiring low cost, soft and flexible operations.

Glove-Based Virtual Interaction for the Rehabilitation of Hemiparesis Stroke Patient

This paper proposes the rehabilitation of a stroke patient by using dataglove called GloveMAP. GloveMAP is a low cost hand glove developed by using the flexible bending sensor and an accelerometer attached at the position of the fingers and wrist, respectively. In the studies, 22 fundamental movements of arm are evaluated and the results are employed to design the virtual environment. The combination of these fundamental movements focuses on Hemiparesis sufferers which are the most common in the stroke and have the inability to move one side of the body. The experimental results show the preliminary studies to investigate muscle activities. The research outcomes are used to design the rehabilitation based virtual environment (VR).

Development of Flexible Pneumatic Cylinder with Built-in Flexible Linear Encoder and Flexible Bending Sensor

Development of Flexible Pneumatic Cylinder with Built-in Flexible Linear Encoder and Flexible Bending Sensor

Measurement of the Flexible Bending Force of the Index and Middle Fingers for Virtual Interaction

In this paper the development of a new low cost dataglove based on fingertip bending tracking techniques for measuring the fingers bending on various virtual interaction activities is presented as an alternative to the rehabilitation services enhancement in the betterment of the quality of life especially for the disabled person. The purpose of the research is to design a flexible control for measurement study of virtual interaction of index and middle fingers that are important in a variety of contexts as well as the deterministic approach. These analyses of fingers flexing of the system were using the flexible bend sensor functioning as a key intermediate of the process to track the fingertip positions and orientations. The main propose of the low cost dataglove is to provide natural input control of interaction in virtual, multimodal and tele-presence environments as an input devices provide as they can monitor the dexterity and flexibility characteristics of the human hand motion. Preliminary experimental results have shown that the dataglove capable to measure several human Degree of Freedom (DoF), “translating” them into commands for the interaction in the virtual world.

Development of string-type flexible displacement sensor to measure the movement of robot and human body

The purpose of our study is to develop a flexible displacement and bending sensor which can measure the movement of human body, flexible actuator or flexible joint of the robot. The string type flexible displacement sensor (FDS for short) consists of two fixed electrodes, a slide electrode and a nylon string coated with carbon (NSCC for short). The flexible bending sensor was developed to measure the bending angle for various bending directions such as the movement of flexible joint of robot. The sensor consists of four tested FDSs, a coil spring and two plastic covers. Four FDSs are arranged in parallel at the position of 90° from the longitudinal center axis of the coil spring. The NSCCs are installed through the coil spring. The skin displacement sensor was developed using FDS to measure the movement of human body by measuring the displacement of the skin.

307 圧電材料を用いた曲げ変形センサによる関節角度計測に関する研究

This paper showed that a very thin, flexible bending sensor was able to be composed by laminating a polymer piezoelectric film (PVDF film) and processing the electrode geometry appropriately. Moreover, the angle such as the elbow joints of the human body was measured with a developed sensor. A variety of electrode patterns are molded on the surface of a polymer piezoelectric film accumulated by the laser beam machining. It was experimentally clarified that problem of the bending deformation sensor developed before using PVDF film.