ABSTRACT
Recently, there has been an escalating demand for advanced materials with superior magnetic properties, especially in the actuator domain. High coercivity (Hci), an essential magnetic property, is pivotal for programmable shape changes in magnetic actuators and profoundly affects their performance. In this study, a new Sm2Fe17-xCuxN3 magnet with a high Hci was achieved by modifying the temperature of the reduction-diffusion processâlowering it from 900 to 700 °C through the introduction of Cu and finer control over the structure and morphology of the Sm2Fe17-xCuxN3 magnetic component within the actuator composite. Consequently, the Sm2Fe17-xCuxN3 magnet demonstrated a remarkable Hci of 11.5 kOe, eclipsing the value of 6.9 kOe attained by unalloyed Sm2Fe17N3 at reduced temperatures. By capitalizing on the enhanced magnetic properties of the Sm2Fe17-xCuxN3 composite and incorporating poly(ethylene glycol) into the elastomer matrix, we successfully fabricated a robust actuator. This innovative approach harnesses the strengths of hard magnets as actuators, offering stability under high-temperature conditions, precision control, longevity, wireless functionality, and energy efficiency, highlighting the vast potential of hard magnets for a range of applications.
ABSTRACT
This study introduces an approach to overcome the limitations of conventional pressure sensors by developing a thin and lightweight composite film specifically tailored for flexible capacitive pressure sensors, with a particular emphasis on the medium and high pressure range. To accomplish this, we have engineered a composite film by combining polyvinylidene fluoride (PVDF) and graphite nanoplatelets (GNP) derived from expanded graphite (Ex-G). A uniform sized GNPs with an average lateral size of 2.55av and an average thickness of 33.74 av with narrow size distribution was obtained with a gas-induced expansion of expandable graphite (EXP-G) combined with tip sonication in solvent. By this precisely controlled GNP within the composite film, a remarkable improvement in sensor sensitivity has been achieved, surpassing 4.18 MPa-1 within the pressure range of 0.1 to 1.6 MPa. This enhancement can be attributed to the generation of electric charge from the movement of GNP in the polymer matrix. Additionally, stability testing has demonstrated the reliable operation of the composite film over 1000 cycles. Notably, the composite film exhibits exceptional continuous pressure sensing capabilities with a rapid response time of approximately 100 milliseconds. Experimental validation using a 3 × 3 sensor array has confirmed the accurate detection of specific contact points, thus highlighting the potential of the composite film in selective pressure sensing. These findings signify an advancement in the field of flexible capacitive pressure sensors that offer enhanced sensitivity, consistent operation, rapid response time, and the unique ability to selectively sense pressure.
