Flexible, structured MWCNT/PDMS sensor for chronic vascular access monitoring

Graft wall pulsation amplitude sensing can provide a measure of functional status, e.g. in hemodialysis access grafts. Current implantable graft monitoring sensors require graft modification and direct bloodstream contact. We propose a new class of piezoresistive flexible pulsation sensors which can be wrapped around the graft to measure wall movement. These sensors must be highly flexible to prevent graft constriction; typical strain sensors are too rigid and the strain sensing range is too limited for this application. We describe a novel additive manufacturing (AM) method for printing polydimethylsiloxane (PDMS) with an internal porous structure, such that material compliance may be tuned anisotropically for a given sensor geometry. Prototype flexible pulsation sensors (FPS) consisting of structured PDMS with an embedded conductive PDMS sensor layer were fabricated and tested. Initial tests demonstrated reliable sensor response to 1-Hz cyclic elongation of 20%, and a sensor gauge factor of 1.0.