Using a Paper Carrier to Screen Print on Polyurethane Film and Fabricate ECG Probes

Flexible, printed and skin-mounted sensors are increasingly used to support long-term monitoring of vital signs. One challenge in printing on-skin devices is in identifying substrates which both match the properties of the epidermis and can tolerate the temperatures required to cure ink. This work describes a method for screen printing on polyurethane (PU) films using a paper ‘carrier’ during the curing process. We printed Ag/AgCI on
$\mathbf{Tegaderm}^{\mathbf{TM}}$
film (3M), demonstrating that carrier bound prints do not shrink or lose conductivity when exposed to temperatures as high as
$220\ ^{\circ}\mathrm{C}$
. We also printed capacitive electrocardiography sensors on Tegaderm, where the electrode connects to the skin with a layer of adhesive which acts as a dielectric. These probes were able to acquire signals with discernible waveform features (P-Q-R-S-T), exhibiting an signal-to-noise ratio of 32.8 dB and a skin-contact impedance at 30 Hz of 648
$\pm 278\Omega$
(standard deviation).