Method for generating one or more strain measurements associated with a biological surface
Inventors
Majerus, Steve JA • Dunning, Jeremy • Bogie, Katherine M. • Potkay, Joseph A
Assignees
Case Western Reserve University • US Department of Veterans Affairs
Publication Number
US-12364434-B2
Publication Date
2025-07-22
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 provides a sensor apparatus and a method for making the sensor apparatus that includes at least one substrate layer made of an elastically deformable material extending longitudinally between spaced apart ends. A conductive layer is disposed over the substrate layer(s) and comprises an electrically conductive material that forms a strain gauge. The strain gauge exhibits an electrical resistance varying based on deformation of the conductive layer in at least one direction, enabling strain measurement.
The sensor apparatus can be composed of multiple substrate layers and the conductive layer can be sandwiched between these substrate layers. The layers can be fabricated using additive manufacturing processes that deposit elongated strands of material with configurable spacing and orientation, providing anisotropic or isotropic compliance. This structural configuration allows the sensor to be strain-sensitive along predetermined directions while less compliant and strain-insensitive in transverse directions.
The problem solved by the invention addresses limitations of existing sensors for monitoring biological conditions such as blood flow in grafts. Conventional sensors that contact bloodstream may stimulate hypercellular processes accelerating graft failure and/or alter graft mechanical structure. The invention provides a sensor with compliance commensurate or greater than the tubular biological or synthetic structure it monitors, enabling external strain measurement without adversely affecting blood flow or graft integrity.
Claims Coverage
The patent includes multiple independent claims covering sensor apparatus systems with key inventive features focusing on substrate and conductive layer configurations and measurement systems with wireless interfaces.
Sensor apparatus with elastically deformable substrate and piezoresistive strain gauge having anisotropic or isotropic compliance
A sensor apparatus comprising at least one elastically deformable substrate layer extending longitudinally between spaced apart ends, combined with a conductive layer disposed as a piezoresistive strain gauge over the substrate. The conductive layer includes electrically conductive material configured to form a strain gauge having anisotropic or isotropic compliance. The system includes a measurement system with a wireless communication interface adapted to transmit measurement data to a remote device.
Measurement system with circuitry measuring electrical resistance between electrical contacts of sensor apparatus
The measurement system includes circuitry configured to measure electrical resistance between first and second electrical contacts of the sensor apparatus, facilitating resistance-based strain data acquisition.
Sensor apparatus with data storage and processing capability
The sensor apparatus stores the measured electrical resistance as measurement data in memory and may include a processor adapted to process this data to provide information such as pressure and/or blood flow through the sensed site.
Sensor apparatus system including a plurality of substrate layers with conductive layer sandwiched to provide anisotropic or isotropic compliance
A sensor apparatus comprising multiple elastically deformable substrate layers extending longitudinally, with a conductive layer sandwiched between at least two substrate layers. The conductive layer includes electrically conductive material adapted to form a strain gauge exhibiting anisotropic or isotropic compliance. The measurement system includes a wireless communication interface to wirelessly transmit measurement data to a remote device.
Material composition of substrate and conductive layers
The elastically deformable substrate layers are made of polydimethylsiloxane (PDMS), and the conductive layer consists of electrically conductive particles integrated with PDMS.
Anisotropic compliance configuration enabled by strand arrangement in layers
The plurality of substrate layers and the conductive layer are configured with anisotropic compliance to allow deformation along a given direction and inhibit deformation along a transverse direction. Each layer includes strands arranged within 5% deviation of being parallel in directions parallel or transverse to the given direction, with strand direction and spacing defining anisotropic compliance.
Strain-sensitive directionality
The given direction along which strain sensitivity is enabled is longitudinal or radial, aligning the sensor's compliance to expected deformation directions.
The independent claims cover a sensor apparatus system comprising elastically deformable substrate layers and a conductive piezoresistive layer configured for strain measurement with anisotropic or isotropic compliance, combined with a measurement system having wireless data transmission capabilities. The inventive features address material composition, layer arrangement, strand orientation, and system communication components to provide flexible, strain-sensitive sensor apparatuses capable of monitoring physiological parameters externally.
Stated Advantages
The sensor apparatus has compliance commensurate with or greater than the biological or synthetic surface to which it is attached, enabling accurate strain measurement without adversely affecting blood flow or mechanical properties.
The anisotropic compliance of the sensor prevents deformation in undesired directions, improving strain sensitivity and accuracy.
Fabrication via additive manufacturing allows customization of size, geometry, and compliance to suit specific application requirements.
The sensor apparatus, when mounted externally, monitors graft motion and function to detect dysfunction such as occlusion or stenosis without stimulating hypercellular processes.
Wireless communication of measurement data facilitates remote monitoring and alerts for patient care.
Documented Applications
Monitoring graft wall motion and functionality by mounting the sensor apparatus around vascular grafts to measure pulsatile blood flow and detect graft dysfunction.
Measuring strain of biological tissue or synthetic surfaces where deformation in one or more directions corresponds to physiological conditions.
Integration of the sensor apparatus onto surfaces such as vessels or organs (stomach, liver, heart, skin) for biological condition monitoring.
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