Screen Printed Stretchable Electronics

In paper I, we protected readily available conducting silver flakes through a thin coating with gold in a low-toxicity water-based process and demonstrated its use in inks for screen printed corrosion-resistant stretchable conductors. The novel silver-gold flake ink was used to fabricate a functional stretchable near-field communication device. Papers II and III both concern entirely screen printed and inherently stretchable devices, utilizing novel stretchable inks in combination with commercial inks to print vertical stacks. Two electrochemical devices – electrochromic displays and organic electrochemical transistors – were printed and tested under stretched conditions to push the limits of how screen printing can be used in applications for thin and stretchable wearable technology. The results show that the devices can retain electrical function even under practically high strains of 50 % (display) and 100 % (transistor). Finally, in paper IV, we investigate the operational principle of gold nanowire- based stretchable composites and find that interactions on the nano-and microscale differ between composites using the same filler but different elastomers. This study sheds light on the importance of the type of elastomer chosen for composites, as this heavily influences the composite’s electrical performance under strain.

Altogether, the studies presented in this thesis provide knowledge, materials, and processes that in the long run can contribute to more effective devices within healthcare and other wearable electronics applications.