###### Abstract  
Electromagnetic responses are generally controlled electrically or optically. However, although electrical and optical control allows fast response, they suffer from switching or tuning range limitations. This paper controls electromagnetic response by mechanical transformation. We introduce a novel kirigami-inspired structure for mechanical transformation with less strength, integrating a shape memory alloy actuator into the kirigami-inspired for mechanical transformation and hence electromagnetic control. The proposed approach was implemented for a reconfigurable antenna designed based on structural and electromagnetic analyses. The mechanical transformation was analyzed with thermal stimulus to predict the antenna geometry and electromagnetic analysis with different geometries predicted antenna performance. We numerically and experimentally verified that resonance response was thermally controlled using the kirigami-inspired antenna integrated with a shape memory alloy actuator.  
electromagnetic control; kirigami-inspired; mechanical transformation; thermal actuator; shape memory alloy; reconfigurable antenna +
Footnote †: journal: Sensors  
operating frequency limitations to increased reliability in dust or moisture impacted environments compared with electrical and optical methods. In addition, the mechanical tuning range can be wider at high frequencies such as millimeter-wave or sub-terahertz spectrum [25]. However, mechanical approaches are generally more complex and costly to implement. Mechanical approaches using origami and kirigami structures have received increasing attention for solving this problem [26; 27; 28; 29]. Origami, which means paper art in Japanese, has been employed in various fields using folding and unfolding structures. Kirigami adds cuts to basic origami structures and hence can implement more complex forms [26; 27; 28; 29].  
Several previous studies have proposed reconfigurable antennas using origami and kirigami structures [30; 31; 32; 33; 34]. For example, [PERSON] et al. [31] proposed an origami quasi-Yagi helical antenna comprising three origami quasi-Yagi helical antennas that fold and unfold to act as driven, director, and reflector elements; and [PERSON] et al. [32] proposed a frequency reconfigurable monopole antenna using kirigami techniques, varying the operating frequency by folded and unfolded three-story tower kirigami structural deformations. [PERSON] et al. [33] proposed a deployable antenna utilizing kirigami pop-up geometry comprised of driven reflectors and a parasitic strip. Origami and kirigami structures allow mechanical transformation with small forces and can be implemented at a low cost.  
This paper proposes mechanical, electromagnetic control using a shape memory alloy (SMA) actuator spring. SMA transforms into its original shape under external environmental stimulus, such as temperature [34]. Thus, the limited operating frequency can be overcome by using the spring as a thermal actuator, which also avoids adding noise, a common problem for motor-based mechanical control. We selected and analyzed a thermally reconfigurable antenna to demonstrate the proposed control. The proposed reconfigurable antenna was a kirigami-inspired structure that varies the operating frequency depending on its model. The proposed SMA actuator spring was transformed by applying a voltage to increase the temperature, changing between the circular patch and circular sector modes with correspondingly different resonance frequencies. In addition, this antenna can be used as a remote high-temperature alarm by modulating the frequency with high and low temperatures. The proposed control was proven numerically and experimentally using the SMA.