Vascular Graft Pressure-Flow Monitoring Using 3D Printed MWCNT-PDMS Strain Sensors

Abstract

Real-time monitoring of arteriovenous graft blood flow would provide early warning of graft failure to permit interventions such as angioplasty or graft replacement to avoid catastrophic failure. We have developed a new type of flexible pulsation sensor (FPS) consisting of a 3D printed elastic cuff wrapped around a graft and thus not in contact with blood. The FPS uses multi-walled carbon nanotubes (MWCNTs) dispersed in polydimethylsiloxane (PDMS) as a piezoresistive sensor layer, which is embedded within structural thixotropic PDMS. These materials were specifically developed to enable sensor additive manufacturing via 3D Bio-plotting, and the resulting strain sensor is more compliant and has a wider maximum strain range than graft materials. Here, we analyze the strain transduction mechanics on a vascular graft and describe the memristive properties of MWCNT-PDMS composites, which may be mitigated using AC biasing. In vitro testing of the FPS on a vascular graft phantom showed a robust, linear sensor output to pulsatile flows (170–650 mL/min) and pressures (62–175 mmHg). The FPS showed an RMS error when measuring pressure and flow of 7.7 mmHg and 29.3 mL/min, with a mean measurement error of 6.5% (pressure) and 8.0% (flow).

Vascular Pressure–Flow Measurement Using CB-PDMS Flexible Strain Sensor

“…Unlike metals or other piezoelectric polymers, these elastomeric strain sensors can measure >20% strain without damage [20]. Prior work established that polydimethylsiloxane (PDMS) doped with conductive particles or nanotubes demonstrated a robust piezoresistive strain response over large strain ranges [20][21][22][23][24][25].…”

“…Here, we expand upon previous work using carbon black (CB) nanoparticle polydimethylsiloxane (PDMS) composite PDMS (CB-PDMS) [25] as a strain sensitive biomaterial for FPS applications. We present an analysis of pressure-flow transduction using a strain sensor wrapped around a blood vessel and select an optimum CB-PDMS composite from mechanical and electrical characterization.…”

3D Printed Flexible Strain Sensors: From Printing to Devices and Signals

“…To further enhance the mechanical properties of PDMS substrate in printed strain sensor, fumed silica nanoparticles have been added into PDMS, the reinforced PDMS composites were endowed with remarkable tensile strength and temperature resistance. [65] However, the viscosity of the uncured composites increases sharply, therefore, tetrahydrofuran or toluene usually were required for ink dilution. The reinforcement of nanoparticles enlarges the spacing between the conductive fillers, which would weaken the conductivity of sensors.…”

Non‐hermetic packaging of biomedical microsystems from a materials perspective: A review

“…Flexible polymeric materials, such as thermoplastic polyurethanes (TPUs) (Bergmeister et al, 2015), polyimide (Palopoli‐Trojani et al, 2016; Rubehn & Stieglitz, 2010; Woods et al, 2018), parylene (Agarwal et al, 2018; Chang et al, 2013; Lecomte et al, 2017; Rodger et al, 2006; Shapero et al, 2016), polydimethylsiloxane (PDMS; Lachhman et al, 2012; Wang et al, 2015; Aceros, Yin, et al, 2012; Ko, Wang, & Lachhman, 2015; Brancato, Weydts, Oosterlinck, Herijgers, & Puers, 2017; Chong, Lou, Bogie, Zorman, & Majerus, 2019; Guo et al, 2013; Kim, Lee, et al, 2012; Lee & Cho, 2005; Lin et al, 2018; Majerus et al, 2018; Majerus, Dunning, Potkay, & Bogie, 2017) and liquid crystal polymer (LCP) (Lee et al, 2011), (Chen et al, 2006; Dean, Pack, Sanders, & Reiner, 2005; Jeong et al, 2015; Park, Jeong, Moon, Kim, & Kim, 2016; Schuettler & Stieglitz, 2013), have many properties that are attractive for non‐hermetic packaging. Table 1 offers a summary of these properties.…”