Large Area Flexible Terahertz Textile Metamaterial

The terahertz and millimeter wave band of the electromagnetic spectrum has been underdeveloped due to the lack of naturally occurring materials that respond at these frequencies. Artificially designed metamaterials offer to fill this terahertz gap by engineering constituent resonant unit cells in large periodic or quasi-periodic arrays. In fact terahertz metamaterials have been developed to demonstrate quite unique properties, such as perfect absorption, amplitude modulation, imager, spatial light modulation, beam steering etc.[1-6] However, current approaches to realizing metamaterials is limited in size to few centimeters and are always rigid due to reliance on expensive cleanroom fabrication process. To truly revolutionize the field of devices that exploit terahertz-matter interaction, we need approaches that allow for large area (meters) metamaterials with arbitrary flexibility and stretchability. Towards that goal, the utilization of common fabrics and advanced textile processing such as stitching or embroidering to design flexible stretchable metamaterial devices on them adds a new dimension enabling terahertz applications. This work presents a millimeter wave and terahertz metamaterial fabrication process on a textile substrate. The fabrication process employs commonly available materials such as pure copper polyester taffeta fabric (PCPTF), thermally activated adhesive mesh, paper adhesive sheets and polyester cotton-based fabric processed using modified textile processing. The material options can be easily expanded to other textile materials in the future. The fabrication process is based on a combination of thermally adhering different materials, laser cutting the metamaterial pattern and peeling the fiducial conductive layer from the final design. A fabrication accuracy down to 0.7mm was easily achieved. It was reproduced eleven times to validate the proposed construction process. The measured average values of the transmission coefficient, and resonance frequency of the designed metamaterial absorbers were 0.09 and 88GHz, respectively. Moreover, the standard deviations of measured transmission coefficient, and resonance frequency equal 0.05 and 0.9GHz, respectively. Interestingly, we realized large area patterns exceeding 10s of centimeters easily, achieved for the first time in literature at these frequencies. These results confirm that novel process flow employing a combination of laser processing, screen printing and textile processing allows realization of large area textile terahertz metamaterials. This will open up new avenues for applications of terahertz metamaterials for the first time.<br/><br/>[1] D. Shrekenhamer, S. Rout, A. Strikwerda, C. Bingham, R. Averitt, S. Sonkusale, and W. Padilla, "High speed terahertz modulation from metamaterials with embedded high electron mobility transistors," Opt. Express 19, 9968-9975 (2011).<br/>[2] X. Liu<i>, </i>S. MacNaughton<i>, </i>D. B. Shrekenhamer<i>, </i>H. Tao<i>, </i>S. Selvarasah<i>, </i>A. Totachawattana<i>, </i>R. D. Averitt<i>, </i>M. R. Dokmeci<i>, </i>S. Sonkusale<i>, and </i>W. J. Padilla, "Metamaterials on parylene thin film substrates: Design, fabrication, and characterization at terahertz frequency", Appl. Phys. Lett. 96, 011906 (2010).<br/>[3] Saroj Rout<i> and </i>Sameer R. Sonkusale, "A low-voltage high-speed terahertz spatial light modulator using active metamaterial", APL Photonics 1, 086102 (2016).<br/>[4] Sameer Sonkusale, Wangren Xu, Saroj Rout, Guoqing Fu, Pramod Singh, "Terahertz metamaterials for modulation and detection," Proc. SPIE 9483, Terahertz Physics, Devices, and Systems IX: Advanced Applications in Industry and Defense, 948306 (2015)<br/>[5] Aydin Sadeqi, Hojatollah Rezaei Nejad, and Sameer Sonkusale, "Low-cost metamaterial-on-paper chemical sensor," Opt. Express <b>25</b>, 16092-16100 (2017).<br/>[6] Pramod K. Singh<i>, </i>Konstantin A. Korolev<i>, </i>Mohammed N. Afsar<i>, and </i>Sameer Sonkusale, "Single and dual band 77, 95, 110GHz metamaterial absorbers on flexible polyimide substrate", Appl. Phys. Lett. 99, 264101 (2011).