Laser ablation as a rapid prototyping approach for fabricating metallic antennas on soft polymer substrates

Quick and easy prototyping methods are beneficial for accelerated product development, allowing for concepts to be realised through quick experimentation, validating predictions based on theory and modelling. A rapid subtractive method for the fabrication of metallic antennas, using laser ablation is reported here. These antennas may be designed for a wide range of wireless power reception applications, as integral parts of a powered device. In line with typical application in sub-dermal implants, we designed the antennas in this work to operate at distances similar to that of the dermis. Inductive spiral coil designs are fabricated from gold on a biocompatible soft polymer, Polydimethylsiloxane (PDMS). PDMS has low dielectric constant of 2.32-2.40 and low loss tangent of 0.04-0.06, which is advantageous for use as antenna substrate. The fabricated inductive coils on PDMS are characterized through electrical impedance spectroscopy and tested as a wireless signal receiver, coupled with a Qi standard wireless transmitting module, at an operating frequency of 100 kHz. Importantly, the fabricated coils show resonance in the operational frequency range of the Qi standard (100 kHz to 125 kHz). This is the first instance of laser ablation defined spiral antennas on biocompatible elastomeric substrates. Although the PDMS based inductive coils have high impedance of 2800 ± 300 Ω at 100 kHz, owing to the mechanical mismatch of rigid conductor and flexible substrate, this approach shows promise. Furthermore, strategies to decrease the impedance of such PDMS-based devices are also discussed.