RESUMEN
Electromagnetic pollution presents growing challenges due to the rapid expansion of portable electronic and communication systems, necessitating lightweight materials with superior shielding capabilities. While prior studies focused on enhancing electromagnetic interference (EMI) shielding effectiveness (SE), less attention is given to absorption-dominant shielding mechanisms, which mitigate secondary pollution. By leveraging material science and engineering design, a layered structure is developed comprising rGOnR/MXene-PDMS nanocomposite and a MXene film, demonstrating exceptional EMI shielding and ultra-high electromagnetic wave absorption. The 3D interconnected network of the nanocomposite, with lower conductivity (10-3-10-2 S/cm), facilitates a tuned impedance matching layer with effective dielectric permittivity, and high attenuation capability through conduction loss, polarization loss at heterogeneous interfaces, and multiple scattering and reflections. Additionally, the higher conductivity MXene layer exhibits superior SE, reflecting passed electromagnetic waves back to the nanocomposite for further attenuation due to a π/2 phase shift between incident and back-surface reflected electromagnetic waves. The synergistic effect of the layered structures markedly enhances total SE to 54.1 dB over the Ku-band at a 2.5 mm thickness. Furthermore, the study investigates the impact of hybridized layered structure on reducing the minimum required thickness to achieve a peak absorption (A) power of 0.88 at a 2.5 mm thickness.
RESUMEN
With the recent development of novel miniaturized magnetically controlled microgripper surgical tools (of diameter 4 mm) for robot-assisted minimally invasive endoscopic intraventricular surgery, the surgeon loses feedback from direct physical contact with the tissue. In this case, surgeons will have to rely on tactile haptic feedback technologies to retain their ability to limit tissue trauma and its associated complications during operations. Current tactile sensors for haptic feedback cannot be integrated to the novel tools primarily due to size limitations and low force range requirements of these highly dextrous surgical operations. This study introduces the design and fabrication of a novel 9 mm2, ultra-thin and flexible resistive tactile sensor whose operation is based on variation of resistivity due to changes in contact area and piezoresistive (PZT) effect of the sensor's materials and sub-components. Structural optimization was performed on the sub-components of the sensor design, including microstructures, interdigitated electrodes, and conductive materials in order to improve minimum detection force while maintaining low hysteresis and unwanted sensor actuation. To achieve a low-cost design suitable for disposable tools, multiple layers of the sensor sub-component were screen-printed to produce thin flexible films. Multi-walled carbon nanotubes and thermoplastic polyurethane composites were fabricated, optimized, and processed into suitable inks to produce conductive films to be assembled with printed interdigitated electrodes and microstructures. The assembled sensor's electromechanical performance indicated three distinct linear sensitivity modes within the sensing range of 0.04-1.3 N. Results also indicated repeatable and low-time responses while maintaining the flexibility and robustness of the overall sensor. This novel ultra-thin screen-printed tactile sensor of 110 µm thickness is comparable to more expensive tactile sensors in terms of performance and can be mounted onto the magnetically controlled micro-scale surgical tools to increase the safety and quality of endoscopic intraventricular surgeries.