Implantable, stretchable sensor for continuous biomechanical monitoring of the heart

Inventors

Kight, Ali • Cutkosky, Mark R. • McElhinney, Doff • Pirozzi, Ileana • Liang, Xinyi • Dual, Seraina • Han, Kyung Won

Assignees

Seoul National University • Leland Stanford Junior University

Abstract

A modular approach for strain sensors for large deformations is provided. The strain sensor separates the extension and signal transduction mechanisms using a soft, elastomeric transmission and a high-sensitivity microelectromechanical system (MEMS) transducer. By separating the transmission and transduction, they can be optimized independently for application-specific mechanical and electrical performance. The durability of the strain sensor was evaluated by conducting cyclic loading tests over one million cycles, and the results show negligible drift. Applications of the strain sensor are suitable for human health monitoring as for example an implantable cardiac strain sensor for measuring global longitudinal strain (GLS).

Core Innovation

The invention provides a strain sensor that includes a transmission element and a transduction element. The transmission element is an elongated homogeneous elastomer that defines a width and a height of a cross-sectional area, has a length and a Young’s modulus, and couples a mechanical signal of interest applied to the elastomer to variations in stress onto a capacitive diaphragm. The transduction element includes a MEMS transducer with integrated signal processing and digital communication.

In the disclosed arrangement, the MEMS transducer is a barometric pressure sensor with a capacitive diaphragm. The capacitive diaphragm is attached to the cross-sectional area of an end of the transmission element. When the transmission element acts as a spring and stretches, the normal force at the cross-sectional area of the end increases in proportion to the spring stiffness, and that normal force is then converted into an electrical signal by the transduction element.

The architecture further enables independent selection of the mechanical properties of the elastomer transmission element and the electrical transduction components, while treating the transmission as a spring to mechanically couple strain-induced normal force onto the capacitive diaphragm. The document reports characterization results including high linear strain–pressure correlation, high signal-to-noise ratio, temperature drift mitigation via onboard sensing/compensation, and reduced sensitivity to bending and pressure interference, together with cyclic durability.

Claims Coverage

The partial content provides one independent claim (clm-00001). It covers an elongated homogeneous elastomer transmission element mechanically coupled to a MEMS barometric pressure sensor with a capacitive diaphragm, where normal force resulting from spring stiffness is converted into an electrical signal.

Across the independent claim, the inventive coverage centers on mechanically coupling strain-induced normal force from an elongated homogeneous elastomer spring transmission to a capacitive diaphragm of a MEMS barometric pressure sensor, with conversion to an electrical signal performed by a transduction element that includes integrated signal processing and digital communication.

Stated Advantages

Documented Applications