Electronic sensor and actuator webs for large-area complex geometry cardiac mapping and therapy

Abstract

Curved surfaces, complex geometries, and time-dynamic deformations of the heart create challenges in establishing intimate, nonconstraining interfaces between cardiac structures and medical devices or surgical tools, particularly over large areas. We constructed large area designs for diagnostic and therapeutic stretchable sensor and actuator webs that conformally wrap the epicardium, establishing robust contact without sutures, mechanical fixtures, tapes, or surgical adhesives. These multifunctional web devices exploit open, mesh layouts and mount on thin, bio-resorbable sheets of silk to facilitate handling in a way that yields, after dissolution, exceptionally low mechanical moduli and thicknesses. In vivo studies in rabbit and pig animal models demonstrate the effectiveness of these device webs for measuring and spatially mapping temperature, electrophysiological signals, strain, and physical contact in sheet and balloon-based systems that also have the potential to deliver energy to perform localized tissue ablation.

Fig. 1.

Sensor web designed for epicardial EGM mapping. (A) Layout (Left) and corresponding picture (Right) of a web. (Insets) Magnified views of a pair of electrodes. (B) Optical image of a web after lamination onto tissue followed by dissolution of the silk substrate (Upper) and in free-standing form in a stretched configuration (Lower). (C) In vitro stretching experiment of a web on chicken meat with no slippage up to ∼22% strain. (D) Web on a silk substrate and after mounting on the epicardial surface (E). (F) Magnified image of interconnected electrodes moving synchronously with the underlying tissue. (G) Recorded EGM from electrodes during normal rhythm (Left), rapid pacing at ∼200 bpm (Center), and during tachycardia (Right). (H) EGM activation mapping at several time intervals, showing a depolarization wave front. The right frame provides color scales for potentials.

Fig. 2.

Stretchable temperature sensor web to monitor cryo- and RF ablation. (A) Sensor web, with Inset of a magnified view of a temperature sensor. Four locations, denoted by #1 to #4, were monitored during cryo-ablation. (B) Sensor web on a silk substrate. Dry ice caused cryo-lesions when in direct contact with the epicardial surface (white dotted circle) for ∼1 min. (C) Image of temperature sensor web on the epicardial surface (Upper Left) and lesions formed by cryo-ablation (Upper Right) and RF ablation (Lower). (D) Calibration curve for temperature sensors, showing normalized resistance at each temperature. (Inset) Raw temperature data. (E) Temperature change as a function of time during dry ice application. (F) Computed temperature distribution during cryo-ablation.

Fig. 3.

Fabrication, characterization, and modeling of Si NM strain gauge webs. (A) Optical image of array of strain gauges on a handle wafer. (B) Enlarged view of the red dotted box showing one of eight strain rosettes with longitudinal, diagonal, and transverse Si NM piezoresistors. (C) Optical image of array of eight stretchable strain rosettes on 0.3-mm-thick silicone substrate. (D) Strain distribution in silicone and a Si NM, induced by 10% uniaxial tensile strain. (Left)The longitudinal strains (ε₂₂) in the silicone are uniformly distributed (near 10%) except for the area covered by a longitudinally oriented Si NM; (Center) the ε₂₂ in the Si NM are three orders of magnitude smaller than the applied strain; (Right) the transverse strains (ε₁₁) in the transverse Si NM are negative owing to the Poisson’s effect in the silicone. (E) In vivo test on the beating rabbit heart.

Fig. 4.

Impedance-based contact sensor webs, on collapsible balloon catheters. (A) Optical image of a device (Left), with magnified view (Right), and picture in its deflated state (B). (C) X-ray image of balloon catheter demonstrating contact and noncontact conditions near the superior vena cava in a live porcine model. (D) In vivo tests impedance contact sensors. Inflation and deflation cycling experiments confirm that sudden increases in impedance coincide with the contact event.