Large structure monitoring with a substrate-free flexible sensor system

1. A method of making a substrate-free flexible sensor system, the method comprising:

additively manufacturing, on a sacrificial substrate, a sensor system by performing the steps of:

(a) depositing a first dielectric layer defining a lattice topology, the first dielectric layer comprising a curable material;

(b) depositing an electrically-conductive layer over the first dielectric layer, wherein:

the electrically-conductive layer comprises a curable electrically-conductive material;

the electrically-conductive layer is configured to provide electrical connections to a sensor array; and

the electrically-conductive layer defines a pattern of interconnects;

(c) depositing one or more sensors on the lattice topology, each of the one or more sensors being disposed at a point defined by an intersection of interconnects and electrically connected to the electrical connections; and

(d) depositing a second dielectric layer over the electrically-conductive layer; and

performing a release process, thereby releasing the sensor system from the sacrificial substrate.

2. The method of claim 1 , wherein:

depositing the first dielectric layer comprises the steps of:

printing a layer of a curable first material; and

curing the curable first material using light and/or heat; and

depositing the electrically-conductive layer comprises the steps of:

printing a layer of a curable second material; and

curing the curable second material using light and/or heat.

3. The method of claim 1 , wherein:

depositing the first dielectric layer comprises aerosol jet (AJ) deposition, extrusion-based direct-write microdispensing, roll-to-roll (R2R) printing, gravure printing, screen printing, and/or thermal spray; and

depositing the electrically-conductive layer comprises aerosol jet (AJ) deposition, extrusion-based direct-write microdispensing, roll-to-roll (R2R) printing, gravure printing, screen printing, cold spray, and/or thermal spray.

4. The method of claim 1 , wherein the curable material comprises one or more of:

thermoplastic, wherein the curing is by cooling; and

curable ink, wherein the curing comprises evaporation and/or sintering of a thermal solvent.

5. The method of claim 1 , wherein the sensor is selected from the group consisting of thermocouple, resistance temperature detector (RTD), Wheatstone bridge, piezoelectric wafer, photocells, electrical resistance cell, electrical capacitance cell, and micro-electro-mechanical system (MEMS) cell.

6. The method of claim 1 , wherein the sensor is a piezoelectric cell configured to provide an electrical signal that is representative of a health of a structure.

7. The method of claim 1 , wherein the electrically-conductive material comprises silver, copper, aluminum, gold, platinum, ruthenium, carbon, and/or alloys thereof.

8. The method of claim 1 , wherein the lattice topology is a grid comprising:

a plurality of horizontally-oriented interconnects; and

a plurality of vertically-oriented interconnects;

wherein:

each of the one or more sensors comprises a sensor node; and

an intersection of a horizontally-oriented interconnect and a vertically-oriented interconnect defines a junction selected from the group consisting of a routing junction and a sensor node.

9. The method of claim 1 , wherein:

the lattice topology comprises a honeycomb pattern; and

each of the one or more sensors defines a sensor cell.

10. The method of claim 1 , wherein the lattice topology comprises radial interconnects and azimuthal interconnects.

11. The method of claim 1 , wherein:

the lattice structure is stretchable in at least one dimension; and

the substrate-free flexible sensor system is conformable to a surface having an irregular surface profile.

12. The method of claim 1 , wherein:

the sacrificial substrate is chemically-dissolvable by a dissolvent; and

the dissolvent comprises water, alcohol, limonene, and/or an alkali solution.

13. The method of claim 1 , wherein the sacrificial substrate further comprises a chemically-dissolvable surface coating comprising polyvinyl alcohol, soluble acrylate, and/or polystyrene.

14. The method of claim 1 , wherein the release process comprises precision micro-machining using a laser.

15. The method of claim 14 , wherein the laser is a femtosecond laser.

16. The method of claim 1 , wherein:

the lattice topology defines a perimeter; and

the method further comprises:

additively-manufacturing a plurality of handling tabs disposed around the perimeter; and

additively manufacturing one or more contact pads, each of the one or more contact pads on an associated one or more of the plurality of handling tabs;

wherein the one or more contact pads are configured to provide an electrical connection to the sensor system.

17. The method of claim 1 , wherein additively manufacturing the sensor system further comprises the steps of:

(e) depositing a second electrically-conductive layer over the second dielectric layer, wherein:

the second electrically-conductive layer comprises the curable electrically-conductive material;

the second electrically-conductive layer is configured to provide electrical connections to the sensor array; and

the second electrically-conductive layer further defines the pattern of interconnects; and

(f) depositing a third dielectric layer over the second electrically-conductive layer.

18. An additively-manufactured flexible sensor system having a lattice topology, comprising:

a plurality of interconnects comprising one or more electrically-conductive layers alternately sandwiched between two or more dielectric layers, wherein:

each of the one or more the electrically-conductive layers includes:

silver, copper, aluminum, gold, platinum, ruthenium, carbon, and/or alloys thereof; and

a cured first material base; and

each of the two or more dielectric layers includes a cured second material base; and

the interconnects are configured to provide electrical connections to a sensor array; and

two or more sensors defining the sensor array, each of the two or more sensors being disposed on the lattice topology and electrically-connected to the interconnects;

wherein the additively-manufactured flexible sensor system is configured to be disposed on the surface of an asset.

19. The additively-manufactured flexible sensor system of claim 18 , wherein:

the interconnects are flexible, thereby allowing the lattice topology to conform to a curved surface; and

at least some of the interconnects are stretchable, thereby allowing the lattice topology to conform to a surface having an irregular surface profile.

20. The additively-manufactured flexible sensor system of claim 18 , wherein the lattice topology comprises a structure selected from the group consisting of:

a rectangular structure comprising horizontally-oriented interconnects and vertically-oriented interconnects;

a circular structure comprising radial interconnects and azimuthal interconnects; and

a hexagonal pattern comprising a honeycomb pattern, further comprising a plurality of sensor cells, each sensor cell encompassing a sensor.