Kirigami-Triggered Spoof Plasmonic Interconnects for Radiofrequency Elastronics

Abstract

The flexible and conformal interconnects for electronic systems as a potential signal transmission device have great prospects in body-worn or wearable applications. High-efficiency wave propagation and conformal structure deformation around human body at radio communication are still confronted with huge challenges due to the lack of methods to control the wave propagation and achieve the deformable structure simultaneously. Here, inspired by the kirigami technology, a new paradigm to construct spoof plasmonic interconnects (SPIs) that support radiofrequency (RF) surface plasmonic transmission is proposed, together with high elasticity, strong robustness, and multifunction performance. Leveraging the strong field-confinement characteristic of spoof surface plasmons polaritons, the Type-I SPI opens its high-efficiency transmission band after stretching from a simply connected metallic surface. Meanwhile, the broadband transmission of the kirigami-based SPI exhibits strong robustness and excellent stability undergoing complex deformations, i.e., bending, twisting, and stretching. In addition, the prepared Type-II SPI consisting of 2 different subunit cells can achieve band-stop transmission characteristics, with its center frequency dynamically tunable by stretching the buckled structure. Experimental measurements verify the on-off switching performance in kirigami interconnects triggered by stretching. Overcoming the mechanical limitation of rigid structure with kirigami technology, the designer SPIs exhibit high stretchability through out-of-plane structure deformation. Such kirigami-based interconnects can improve the elastic functionality of wearable RF electronics and offer high compatibility to large body motion in future body network systems.

Fig. 1.

Wireless bodyNETs based on high-elasticity SPI. (A) Conceptual illustration of the body network based on SPIs. The schematic illustration (B) before and (C) after laser cutting metal surface. (D) Illustrated insertion loss vs. frequency for these 2 stretchable SPIs in (C). (E) Dispersion curves of stretchable Type-I SPI and metal surface. (F) Mode 1 (fundamental mode) and mode 2 (second mode) for the stretchable Type-II SPI. The corresponding cutoff frequency is 16.7 GHz.

Fig. 2.

Robust transmission performance of high-elasticity Type-I SPI. (A) (i) Illustration before and after damaging corrugated groove structure; (ii) transmission comparison; (iii) schematic configuration before and after stretching Type-I SPI. The blue arrow (n) indicates the normal vector perpendicular to the facet B. (B) Dispersion curves analysis for the Type-I SPI with different stretchable states. (C) Measured transmission and experimental photograph of the SPI with different deformable states. (D) Simulated (upper) and measured (bottom) z-component near-electric field distributions of the Type-I SPI at 10 GHz.

Fig. 3.

Transmission performance of the Type-II SPI with tunable band stop. (A) Schematic configuration of proposed Type-II SPI. (B) Simulated and (C) measured transmission of the Type-II SPI with different stretching states. Inset: E_z field distributions of the mode 1 and mode 2. (D) Energy transfer histograms of z-component near-electric field distributions (on the plane 3 mm over the deformable Type-II SPI) of the Type-II SPI at 6, 8, and 10 GHz.

Fig. 4.

Experimental verification on on-body wireless signal transmission and mechanical performance of the SPIs. (A) The transmissions and corresponding experimental photos of Type-I SPI with and without textiles worn on arm part. (B) The experimental photos and corresponding transmissions of Type-I and Type-II SPIs worn on belly part of the body. Extracted heartbeat signals of the Tx/Rx pair antenna connecting the (C) commercial coaxial and (D) proposed SPI within 10 s. Force-displacement response and photographs corresponding to different curves process of (E) Type-I and (F) Type-II SPIs.