Evaluation of Piezoresistive Polymer-based Traces for Non-invasive Sensor Patch

In this paper, we shall discuss the suitable alternative material to gold for creating traces or electrodes of a noninvasive flexible sensor patch that is used for detecting early extravasation during intravenous cannulation. The samples were prepared by printing $5 \mu \mathrm{m} -$ to $10 \mu \mathrm{m} -$ thin piezoresistive polymer-based Carbon paste on a base polymer patch, also called the adhesive film. The first samples have the traces embedded in between two base adhesive films. The sensitivity of the samples was characterized by using a pressure chamber/jig with 4 cm hole to mimic an extravasation by bump formation when pumped with compressed dry air (CDA) that is connected to a 15 psi source. The sensitivity value obtained was 20% up to 23% at 0.16 psi. After optimization of the curing temperature of the adhesive film and piezoresistive polymer-based Carbon traces, ex-vivo test was conducted with the prototype sample placed on the cannulation site of a pork front hock. At 2 ml and 5 ml infused fluid, the sensitivity obtained is only 1.1% and 2.44%, respectively. The overall prototype dimension of all samples is 6 × 7 cm2. The second samples were prepared with narrower trace width and spacing than the first samples. Sensitivity obtained from the second sample at 0.16 psi increased to 50% up to 79%. The third samples were prepared with the same narrow trace with as the second sample, but this time the piezoresistive polymer-based traces were not embedded in two adhesive films, making the sample a single layer patch only. Sensitivity obtained at 0.16 psi increased further to 140% up to 200%. The 0.16 psi readout is based on previous data that at this pressure induced in the 4 mm hole where the adhesive film is placed over, it translates to 3mm bump height at 2ml infused volume on the skin. The results suggest a strong potential in the development of the piezoresistive polymer-based Carbon traces for flexible non-invasive sensor patch for early extravasation detection.