AIRBRUSHING AND SURFACE MODIFICATION FOR FABRICATING FLEXIBLE ELECTRONICS ON POLYDIMETHYLSILOXANE
Kartik Sondhi, Seahee Hwangbo, Yong-Kyu Yoon, Toshikazu Nishida and Hugh Fan
Polydimethylsiloxane (PDMS) is known to be more flexible and stretchable than other commonly used substrates for flexible electronics, including thermoplastic polyurethane (TPU) and polyethylene terephthalate (PET). However, commercially available inks for printing flexible electronics are not formulated for PDMS, resulting in very poor adhesion of printed electronic components on PDMS. To address this limitation, we have developed a surface-modification method that enables inks to adhere firmly onto PDMS. Using the ASTM protocols (tape-pull test and pencil-hardness test), we confirmed that the surface modification method significantly improved the adhesion and abrasion resistance of conductive components fabricated on PDMS. In addition, we investigated using an airbrush as a low-cost alternative for fabricating flexible electronics. We compared airbrushing with screen printing, the common fabrication method used for flexible electronics. We found that the change in resistance of resistors airbrushed on both surface-modified PDMS and TPU was slightly less after 30–100 cycles of stretching than the same resistors screen-printed on the same substrates, indicating that airbrushing is able to fabricate electronic components of similar quality, if not better, when compared with screen printing. To further illustrate the effect of the surface modification method and airbrushing, we fabricated a patch antenna by airbrushing inks on surface-modified PDMS and pristine PDMS. The measurement results of the antenna on surface-modified PDMS showed a close agreement with the simulation result, giving a resonant frequency at 2.4 GHz.
Keywords: airbrushing, surface modification , flexible electronics, patch antnna and polydimethylsiloxane