Stretchable electronic circuit
A stretchable electronic circuit that includes a stretchable base substrate having a plurality of stretchable conductors formed onto a surface thereof, with both the stretchable base substrate and conductors being bendable together about two orthogonal axes. The stretchable circuit also includes a stretchable sensor layer attached to the base substrate with a cavity formed therein which has a contact point exposing one of the plurality of stretchable conductors. The stretchable electronic circuit further includes a surface mount device (SMD) package with a conductor contact protrusion installed into the cavity, and wherein a substantially constant electrical connection is established between the conductor contact protrusion and the stretchable conductor at the contact point by tensile forces interacting between the stretchable base substrate and the stretchable sensor layer.
1. A stretchable electronic circuit, comprising:
a stretchable base substrate having a plurality of stretchable conductors formed onto a surface thereof; both the base substrate and conductors being bendable together about at least two orthogonal axes;
a stretchable sensor layer attached to the base substrate and having a surface mount device (SMD) cavity formed therein, the SMD cavity including at least one contact point exposing at least one of the plurality of stretchable conductors; and
an SMD package having a conductor contact protrusion installed into the SMD cavity, wherein tensile forces interacting between the stretchable base substrate and the stretchable sensor layer maintain a substantially constant electrical connection between the conductor contact protrusion and the stretchable conductor at the contact point.
2. The electronic circuit of claim 1 , wherein the stretchable base substrate and stretchable sensor layer further comprise a biocompatible material.
3. The electronic circuit of claim 2 , wherein the biocompatible material is a stretchable PDMS material.
4. The electronic circuit of claim 1 , wherein the SMD package is selected from a group consisting of a light-emitting diode (LED) and a photodiode detector.
5. The electronic circuit of claim 1 , further comprising:
a stretchable connector layer attached to the base substrate and having a connector well formed therein and adjacent to at least one of the plurality of stretchable conductors;
an external interface lead wire having one end installed with the connector well;
flowable conductive material filling the connector well and establishing a substantially constant electrical connection between the lead wire and the stretchable conductor; and
a stretchable cap layer over the connector well securing the lead wire to the stretchable electronic circuit and sealing the flowable conductive material within the connector well.
6. The electronic circuit of claim 5 , wherein the lead wire includes an anchor to inhibit removal from the connector well.
7. The electronic circuit of claim 5 , wherein the flowable conductive material is a liquid metal.
8. The electronic circuit of claim 7 , wherein the liquid metal is at least one of EGaIn, GaInSn and Indalloy 60®.
9. The electronic circuit of claim 5 , wherein the flowable conductive material is a conductive polymer.
10. The electronic circuit of claim 5 , wherein the SMD package further comprises a plurality of light-emitting diodes and photodiode detectors arrayed together, each diode and detector being connected through a connector well to an external interface lead wire and form a sensor system attachable to a curved surface of a human body.
11. The electronic circuit of claim 10 , wherein the sensor system is configured to monitor a function of the human body selected from the group consisting of fingernail blood flow and perfusion, pulse-oximetry, photodynamic therapy and combinations thereof.
12. The electronic circuit of claim 1 , wherein the plurality of stretchable conductors have a buckled non-strained configuration and a stretched configuration.
13. The electronic circuit of claim 1 , wherein the sensor system is configured to monitor fingernail blood flow and perfusion using photoplethysmorgraphy.