Sensitivities of rheological properties of magnetoactive foam for soft sensor technology

Magnetoactive (MA) foam, with its tunable mechanical properties and magnetostriction, has the potential to be used for the development of soft sensor technology. However, researchers have found that its mechanical properties and magnetostriction are morphologically dependent, thereby limiting its capabilities for dexterous manipulation. Thus, in this work, MA foam was developed with additional capabilities for controlling its magnetostriction, normal force, storage modulus, shear stress and torque by manipulating the concentration of carbonyl iron particles (CIPs) and the magnetic field with regard to morphological changes. MA foams were prepared with three weight percentages of CIPs, namely, 35 wt.%, 55 wt.% and 75 wt.%, and three different modes, namely, zero shear, constant shear and various shears. The results showed that the MA foam with 75 wt.% of CIPs enhanced the normal force sensitivity and positive magnetostriction sensitivity by up to 97% and 85%, respectively. Moreover, the sensitivities of the storage modulus, torque and shear stress were 8.97 Pa/mT, 0.021 µN/mT, and 0.0096 Pa/mT, respectively. Meanwhile, the magnetic dipolar interaction between the CIPs was capable of changing the property of MA foam from a positive to a negative magnetostriction under various shear strains with a low loss of energy. Therefore, it is believed that this kind of highly sensitive MA foam can potentially be implemented in future soft sensor systems. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Universiti Teknologi Malaysia through Collaborative Research Grant (CRG) [08G79]; Professional Development Research University (PDRU) [05E21]; Universitas Sebelas Maret, Hibah Non APBN 2021, LPPM-UNS; Ministry of Education, Youth and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [RP/CPS/2020/006]05E21; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Universiti Teknologi Malaysia, UTM: 08G79; Universitas Sebelas Maret, UNS: RP/CPS/2020/00

Enhancement of sensitivity of magnetostrictive foam in low magnetic fields for sensor applications

Magnetostrictive materials are usually used in sensor technology since they are sensitive to magnetization and strain. Unfortunately, to date, only a few magnetostrictive materials are being used, as the need for a strong magnetic field (1 T) and not sensitive at a low magnetic field. Thus, in this study, a new magneto-active (MA) polyurethane foam was fabricated to obtain a strain at a low magnetic field corresponding to below 1 T. The in-situ fabrication of the MA foam was carried out with various compositions of carbonyl iron particles (CIPs), particularly at 35, 45, 55, 65 and 75 wt%. An analysis of the magnetic properties revealed that all the MA foams showed high magnetic saturation with low remanence values. Furthermore, the MA foam of 75 wt% showed the highest magnetostrictive strain of 1.66% at 0.45 T. The sensitivity of the MA foam is 0.0146%/mT with 42% of improvement. Analyses show MA foam of 75 wt% had a low density, biggest pores and long struts that might have led to high flexibility for elongation to produce a high strain percentage within the practical magnetic field range. Hence, this MA foam can be further utilized for sensor applications

Enhancement in Structural and Electroluminescence Properties of Green Light Emission for Semipolar (11–22) InGaN/GaN Based Grown on m-Plane Sapphire via Low Temperature Ammonia Treatment (LTAT)

Research on enhancement green light emitter is important to obtain a perfect red-green-blue (RGB) induced white light source. Unfortunately the present of mixed phase in deposition of InGaN/GaN limited the potential LED efficiency. Therefore, we introduce a new method called as Low Temperature Ammonia Treatment (LTAT) to eliminate the mixed phase and to enhance the structure properties of InGaN/GaN. Two samples have been prepared, with LTAT (LED A) and without LTAT (LED B). Both samples have been characterized using optical microscope (OM), Atomic Force Microscope (AFM), X-ray rocking curve (XRC) and Electroluminescence (EL). On the structural characterization, the OM results show the present 3D island on LED B sample while sample LED A only shows 2D surface. The RMS surface roughness from AFM are 10.3 ± 0.4 nm and 13.5 ± 10.7 nm for LED A and LED B respectively. XRC analysis proved the LED A with LTAT has a homogenous XRD curve while LED B without LTAT has a mixed phase. The BSFs streak length measured as 1.42 nm−1 and 1.61 nm−1 for LED A and LED B respectively shows low crystallographic defect in LED A compared to LED B. For the EL characteristic, LED A shows a single sharp peak near 538.2 nm wavelength, while LED B shows a broad multi-peak profile at 435.7 nm, 480.6 nm and 520.5 nm. The single sharp peak shows enhancement in green light emission when LTAT is applied during deposition. Successful enhancement is structural and electroluminescence properties shows the effectiveness of LTAT proposed in this work for perfect RGB

Enhancement in Structural and Electroluminescence Properties of Green Light Emission for Semipolar (11–22) InGaN/GaN Based Grown on m-Plane Sapphire via Low Temperature Ammonia Treatment (LTAT)

Research on enhancement green light emitter is important to obtain a perfect red-green-blue (RGB) induced white light source. Unfortunately the present of mixed phase in deposition of InGaN/GaN limited the potential LED efficiency. Therefore, we introduce a new method called as Low Temperature Ammonia Treatment (LTAT) to eliminate the mixed phase and to enhance the structure properties of InGaN/GaN. Two samples have been prepared, with LTAT (LED A) and without LTAT (LED B). Both samples have been characterized using optical microscope (OM), Atomic Force Microscope (AFM), X-ray rocking curve (XRC) and Electroluminescence (EL). On the structural characterization, the OM results show the present 3D island on LED B sample while sample LED A only shows 2D surface. The RMS surface roughness from AFM are 10.3 ± 0.4 nm and 13.5 ± 10.7 nm for LED A and LED B respectively. XRC analysis proved the LED A with LTAT has a homogenous XRD curve while LED B without LTAT has a mixed phase. The BSFs streak length measured as 1.42 nm−1 and 1.61 nm−1 for LED A and LED B respectively shows low crystallographic defect in LED A compared to LED B. For the EL characteristic, LED A shows a single sharp peak near 538.2 nm wavelength, while LED B shows a broad multi-peak profile at 435.7 nm, 480.6 nm and 520.5 nm. The single sharp peak shows enhancement in green light emission when LTAT is applied during deposition. Successful enhancement is structural and electroluminescence properties shows the effectiveness of LTAT proposed in this work for perfect RGB

Prediction for magnetostriction magnetorheological foam using machine learning method

Magnetorheological (MR) foam is a magnetic polymer composite (MPC) that can be used for soft sensors and actuators in soft robotics. Modeling mechanical properties and magnetostriction behavior of MR foam is critical to developing into MR foam devices. This study uses extreme learning machines (ELM) and artificial neural networks (ANN) to predict magnetostriction behavior. These models describe the nonlinear relationship between different carbonyl iron particle compositions, magnetic field, strain, and normal force. The model's hyperparameters (learning algorithms and activation functions) are varied. For ANN, RMSProp, and ADAM learning algorithms were used with sigmoid and ReLU activation functions. The ELM model considered the Hard limit, ReLU, and sigmoid activation function. The model was then evaluated for both training and testing data. Based on the results, ANN RMSProp Sigmoid, ELM with activation function ReLU, and Hard limit are more accurate than other models. However, the correlation analysis and comparison between prediction and experimental data show ELM Hard limit are more generalized in predicting strain and normal force with (Formula presented.), 0.999, and RMSE less than 0.002. In conclusion, the ELM Hard limit model accurately predicts the magnetostriction behavior of MR foam, paving the way for future MR foam device development

Characterization of morphological and rheological properties of rigid magnetorheological foams via in situ fabrication method

This paper presents material characteristics of a rigid magnetorheological (MR) foam that comprises polyurethane foam matrix and carbonyl iron particles (CIPs). Three different samples of MR foams are prepared by changing the concentration of CIPs (0, 35, and 70 g) in isotropic condition. In-depth characterization on the morphological properties, the field-dependent rheological behavior in terms of linear viscoelastic region and storage modulus, and the off-state sound absorption properties are then experimentally investigated. In the morphological observation, it is seen from the fluorescence micrographs that MR foam consists of open pore structure and the average size of the pores is decreased with the increment in CIPs content. In the rheological test of MR foam, it is identified that MR foam with the addition of 70 g of CIPs to the total of polyol and isocyanates (100 g) can enhance the storage modulus up to 112% compared with MR foam without CIPs. In the meantime, from the acoustic absorption test, it is shown that the maximum peaks of sound absorption coefficient (SAC) are shifted to the low frequency and the SAC is increased up to 229% due to the decrement in the pores size and increment in the storage modulus. The results achieved from this material characterization of MR foam provide useful guidelines for the development of new type smart materials associated with MR fluids and for the findings of appropriate applications which require controllability of both the stiffness and acoustic properties