Elastomer Encapsulated Silver Nanorod Dispersed Polyacrylamide-Alginate Hydrogel for Water-Pressure-Dependent EMI Shielding Application

Abstract

Smart electromagnetic interference (EMI) shielding materials with tunable EMI shielding effectiveness (SE) have garnered huge attention in the fabrication of next generation EM devices as well as innovative wearable electronics. Here, we report a polydimethylsiloxane (PDMS) encapsulated soft, flexible, and stretchable polyacrylamide (PAM)-alginate (Alg)-hydrogel/silver nanorod (AgNR) composite system for EMI SE application. The PDMS encapsulation not only enhances the tensile strength of the system from ∼0.057 MPa to ∼0.724 MPa but also restricts the evaporation of water from the hydrogel matrix. Consequently, at 14.5 GHz frequency, the EMI SE (∼48.72 dB) of the hydrogel was reduced to ∼10.52 dB (72 h at 30 °C) and ∼6.44 dB (72 h at 40 °C) and ∼8.03 dB after 1 week of settlement at ambient conditions. However, for the encapsulated hydrogel, the EMI SE (∼40.65 dB) value was marginally reduced to ∼33.86 dB, ∼31.45 dB, and ∼32.42 dB, respectively, under the same conditions. Moreover, by changing the sample thickness (increasing holding pressure in a VNA sample holder), the shielding performance can be altered from ∼48.72 to ∼53.63 dB for the hydrogel and from ∼40.65 to ∼44.03 dB for the encapsulated hydrogel. Thus, these findings provide an innovative strategy to fabricate a flexible and stretchable EMI shielding material with adjustable SE by varying the content of water and applying pressure for futuristic development in smart electronics.

Ionic liquid-dispersed PDMS/SWCNT/Ag@Ni hybrid composite for temperature- and pressure-sensitive smart electromagnetic shielding applications

“…However, the entire loss in terms of dielectric and magnetic losses are defined in a single entity, i.e. , by the attenuation constant computed for all samples using eqn (1), as follows: 3,17,18 where f is the frequency and c is the light velocity. The concentration-dependent α results for the studied composites are displayed in Fig.…”

“…The Ku frequency (14–18 GHz) band is used in the uplink of very-small-aperture terminals (VSAT) for modern satellite communications and space shuttle communication. 3,13,14…”

“…Additionally, this absorption performance of the water can presumably be enhanced by using aqueous ionic solutions, which attenuates the incident electromagnetic radiation through the orientation polarization of dipolar water molecules and the ionic conduction of mobile ions. 3…”

“…The use of these devices results in the emission of a high density of EM radiation to the environment, for example, 5G communication devices emit 10-times more radiation than 4G devices. [1][2][3] This causes severe EM pollution, which threatens human health and data security. [3][4][5] Thus, there is a direct correlation between these technological innovations and the development of intelligent materials that can change their properties in response to operational environmental inputs such as heat, mechanical stress, moisture, and pH.…”

“…[1][2][3] This causes severe EM pollution, which threatens human health and data security. [3][4][5] Thus, there is a direct correlation between these technological innovations and the development of intelligent materials that can change their properties in response to operational environmental inputs such as heat, mechanical stress, moisture, and pH.…”