Polydimethylsiloxane membranes for millimeter-wave planar ultra flexible antennas

Abstract

We present here the use of polydimethylsiloxane (PDMS) membranes as a new soft polymer substrate (εr ≈ 2.67 at 77 GHz) for the realization of ultra-flexible millimeter-wave printed antennas thanks to the extremely low Young's modulus (EPDMS < 2 MPa). Ultimately this peculiar property enables one to design wide-angle mechanically beam-steering antennas and flexible conformal antennas. The experimental characterization of PDMS material in V- and W-bands highlights high loss tangent values (tanδ ≈ 0.04 at 77 GHz). Thus micromachining techniques have been developed to reduce dielectric losses for antenna applications at millimeter waves. Here the antenna performance is demonstrated in the 60 GHz band by considering a single microstrip patch antenna supported by a PDMS membrane over an air-filled cavity. After a brief description of the design approach using the method of moments (MoM) and the finite-difference time-domain (FDTD) technique, the technological processes are described in detail. The input impedance and radiation patterns of the prototype are in good agreement with numerical simulations. The radiation efficiency of the micromachined antenna is equal to 60% and is in the same order as that obtained with conventional polymer bulk substrates such as Duroids. These results confirm the validity of the new technological process and assembly procedure, and demonstrate that PDMS membranes can be used to realize low-loss planar membrane-supported millimeter-wave printed circuits and radiating structures.

Reversibly Deformable and Mechanically Tunable Fluidic Antennas

“…These devices are useful in millimeter-wave applications (e.g., automotive radars, security, and surveillance systems, and high-data-rate wireless communication systems). [4] Mechanically scanned antennas-that is, devices in which a portion of the antenna is designed to bend out of plane-are being explored for these applications because they are less expensive, more efficient, and offer better control than electronic phase shifting arrays. [4][5][6][7] Most conventional antennas are fabricated by milling or etching rigid sheets of copper into a static shape that dictates a singular function.…”

Stretchable Microfluidic Radiofrequency Antennas

“…Antennas offer new, attractive applications for stretchable electronics, such as reconfigurable antennas, [7] antennas for limited and non-planar spaces, [8] and wearable sensors. Two methods are commonly used to build antennas.…”

Microwave Dielectric Heating of Fluids in Microfluidic Devices

“…The absorption ratio obtained for the device with empty channel (■) is due to ohmic dissipation in the thin-film CPW, which can be modeled by an attenuation constant, cpw, which corresponds to 2.86 dB/cm at 10 GHz. The attenuation constant of PDMS is assumed to be negligible because of the relatively low values of loss tangent (the ability of a material to convert stored electrical energy into heat) at microwave frequencies (Tiercelin et al, 2006). An increase in A observed with increasing frequency for the empty channel device (■) is expected from the dependence of skin depth on frequency.…”