Sensor apparatus and method of making same
Inventors
Majerus, Steve J A • Dunning, Jeremy • Bogie, Katherine M. • Potkay, Joseph A.
Assignees
Case Western Reserve University • US Department of Veterans Affairs
Publication Number
US-11576612-B2
Publication Date
2023-02-14
Expiration Date
2038-10-12
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Abstract
A sensor apparatus includes at least one substrate layer of an elastically deformable material, the substrate layer extending longitudinally between spaced apart ends thereof. A conductive layer is attached to and extends longitudinally between the spaced apart ends of the at least one substrate layer. The conductive layer includes an electrically conductive material adapted to form a strain gauge having an electrical resistance that varies based on deformation of the conductive layer in at least one direction.
Core Innovation
The invention relates to a sensor apparatus and a method of making a sensor that includes at least one substrate layer of an elastically deformable material extending longitudinally between spaced apart ends. A conductive layer is attached and extends longitudinally between the spaced apart ends of the substrate layer. This conductive layer includes an electrically conductive material adapted to form a strain gauge, whose electrical resistance varies based on deformation of the conductive layer in at least one direction.
The sensor apparatus may comprise multiple layers arranged to provide anisotropic compliance, enabling strain sensitivity along a predetermined direction while being less compliant and strain-insensitive in a transverse direction. The conductive layer can be configured in various patterns, such as strips in a zig-zag or serpentine shape, integrated between substrate layers that are deposited using additive manufacturing techniques, which allows control over strand orientation and spacing to tune compliance and elasticity.
The problem addressed is that existing sensors for monitoring biological conditions such as grafts require contact with the bloodstream, which may stimulate hypercellular processes leading to accelerated graft failure or altered graft mechanical structure. This invention provides a more compliant, strain-sensitive sensor that can be mounted externally to vascular grafts and other biological tissues to monitor deformation and thus indirectly assess blood flow and graft function without adversely affecting the graft or blood flow.
Claims Coverage
The claim coverage includes one independent system claim and one independent method claim describing the sensor apparatus, measurement system, and use of the sensor.
Sensor apparatus with elastically deformable substrate and strain gauge conductive layer
The sensor apparatus comprises at least one substrate layer of an elastically deformable material extending longitudinally between spaced apart ends, with a conductive layer attached and extending longitudinally between these ends. The conductive layer includes an electrically conductive material forming a strain gauge whose electrical resistance varies based on deformation in at least one direction.
Integration of measurement system with wireless communication interface
The system includes a measurement system configured to measure electrical resistance of the sensor apparatus and a wireless communication interface to transmit measurement data wirelessly to a remote device.
Anisotropic compliance through multiple substrate layers and strand arrangement
The sensor apparatus includes multiple substrate layers with the conductive layer sandwiched between at least two substrate layers. These layers are configured with strands oriented parallel or transverse to a given direction, with spacing defining anisotropic compliance that enables deformation along a given direction but inhibits deformation transversely.
Use of polydimethylsiloxane (PDMS) and conductive particles integration
The elastically deformable substrate layers comprise PDMS, and the conductive layer comprises electrically conductive particles integrated with PDMS, forming a piezoresistive strain gauge sensitive along a longitudinal or radial direction.
Method of deploying sensor apparatus to biological surfaces for strain measurement
The method includes advancing the sensor apparatus into a patient, mounting it to a biological surface such as a vessel wall, generating strain measurements, monitoring internal conditions, generating alerts upon dysfunction detection, and communicating alerts to caregivers for possible intervention.
The independent claims cover a sensor apparatus with elastically deformable substrate layers and an electrically conductive strain gauge layer, combined with measurement and wireless communication systems. The apparatus is configured for anisotropic compliance with material and structural design details, and the method claims cover deployment on biological surfaces for monitoring strain and physiological conditions.
Stated Advantages
The sensor apparatus exhibits compliance commensurate with or greater than the biological surface (e.g., vascular graft), enabling accurate monitoring of pulsatile deformation without adversely affecting blood flow.
External mounting of the sensor avoids contact with bloodstream, reducing risks of hypercellular stimulation that may lead to graft failure or structural alteration.
The use of additive manufacturing enables customization of sensor size, geometry, and compliance parameters tailored to specific applications and surfaces.
The anisotropic compliance design allows strain sensitivity in desired directions while inhibiting deformation in transverse directions, enhancing measurement accuracy.
Wireless communication enables remote monitoring and timely alert generation for graft dysfunction, facilitating early intervention and potentially extending graft patency.
Documented Applications
Monitoring graft function, such as detecting flow rate and pressure through vascular or hemodialysis access grafts by measuring deformation-induced changes in electrical resistance.
Mounting on a biological vessel wall or other tissue surfaces to monitor deformation associated with biological conditions like blood flow or muscle contractions.
Integration with measurement and communication systems for real-time monitoring and remote data transmission to smart phones, servers, or wireless receivers.
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