System for Sensing Miniature Gaps by Inductive Coupling

A method for measuring an air gap between a first surface of a first part and a second surface of a second part, comprising:

• adhering first flexible hybrid electronics comprising a first LC circuit formed on a first flexible substrate to the first surface of the first part;
• adhering second flexible hybrid electronics comprising a second LC circuit formed on a second flexible substrate to the second surface of the second part;
• driving a first inductor of the first LC circuit with a first alternating current to produce a changing magnetic flux that passes through a second inductor of the second LC circuit, which first alternating current has a frequency equal to a resonant frequency of the second LC circuit;
• inducing a second alternating current in the second inductor due to the magnetic flux passing through the second inductor;
• rectifying the second alternating current into a first direct current;
• converting the first direct current into first digital gap sensor measurement data that varies in dependence on a first distance separating the first and second inductors;
• transmitting the first digital gap sensor measurement data to a digital signal processor;
• and
• computing a first air gap size based on the first digital gap sensor measurement data, wherein the computing is performed by the digital signal processor.

A method for determining an air gap profile between a first surface of a first part and a second surface of a second part, comprising:

• adhering first flexible hybrid electronics comprising a first multiplicity of inductors formed on a first flexible substrate to the first surface of the first part;
• adhering second flexible hybrid electronics comprising a second multiplicity of inductors formed on a second flexible substrate to the second surface of the second part, the inductors of the second multiplicity of inductors being respectively aligned with the inductors of the first multiplicity of inductors;
• driving the inductors of the first multiplicity of inductors in sequence with respective first alternating currents to produce a changing magnetic flux that passes through respective aligned inductors of the second multiplicity of inductors;
• inducing respective second alternating currents in the respective aligned inductors of the second multiplicity of inductors due to the magnetic flux passing through the respective aligned inductors of the second multiplicity of inductors;
• rectifying the respective second alternating currents into respective direct currents;
• converting the respective direct currents into digital gap sensor measurement data that varies in dependence on the respective distances separating respective aligned inductors of the first and second multiplicities of inductors;
• transmitting the digital gap sensor measurement data to a digital signal processor;
• and
• computing an air gap profile based on the digital gap sensor measurement data, wherein the computing is performed by the digital signal processor.

A method for fabricating a gap sensor, comprising:

• forming a first inductor and a first electrode of a first capacitor on a first dielectric layer, wherein the first inductor is electrically connected to the first electrode of the first capacitor;
• forming a second electrode of the first capacitor on a second dielectric layer;
• bonding the first dielectric layer to the second dielectric layer to form a first flexible substrate with the first capacitor;
• forming a second inductor and a first electrode of a second capacitor on a third dielectric layer, wherein the second inductor is electrically connected to the first electrode of the second capacitor;
• forming a second electrode of the second capacitor on a fourth dielectric layer;
• bonding the third dielectric layer to the fourth dielectric layer to form a second flexible substrate with the second capacitor;
• forming a via in the second flexible substrate;
• and
• forming a conductor that fills the via and electrically connects the second inductor to the second electrode of the second capacitor.