Aerosol jet printed flexible graphene circuits for electrochemical sensing and biosensing

A method of fabrication of graphene-based circuits on a substrate comprising:

• a. preparing a printable ink of pristine graphene flakes of graphene or graphene oxide exfoliated from graphite produced and dispersed in solvents from bulk synthesis solution processing;
• b. creating one or more patterns in one or more passes by scalable, high-throughput direct write additive manufacturing of the printable ink without stenciling or photolithography, and without pre- or post-patterning steps;
• and
• c. post-print annealing the one or more patterns in a CO2 environment effective to convert electrochemically inactive printed graphene into electrochemically active graphene.

A method of fabrication of graphene-based circuits on a substrate comprising:

• a. preparing a printable ink comprising graphene or graphene oxide exfoliated from graphite from a bulk synthesis process;
• and
• b. aerosol jet printing a circuit by direct additive manufacturing on a substrate using said printable ink without stenciling or photolithography for an immunosensor, wherein the immunosensor comprises at least one of:
• i. monitors both IL-10 and IFN-gamma in an actual bovine sample;
• ii. has a biomarkers sensing range of 0.1-10 ng/mL;
• and
• iii. does not require a redox probe (e.g. metal nano particle) or fluorescent label for sensitive or visibility.

A method of fabrication of graphene-based circuits on a substrate comprising:

• a. preparing a printable ink comprising graphene or graphene oxide exfoliated from graphite from a bulk synthesis process;
• and
• b. aerosol jet printing a circuit by direct additive manufacturing on a substrate using said printable ink without stenciling or photolithography, wherein the aerosol jet printing comprises:
• i. no contact with 1-5 mm variable standoff from the substrate;
• ii. a tightly focused continuous stream of ink with 1-5 micron droplets of a viscosity between 1-1,000 cP;
• iii. printer parameters to aerosol jet print thin and continuous graphene ink with minimal satellite droplets comprising:
• sheath flow rates of 40-60 sccm,
• carrier flow rates of 15-45 sccm, and
• printing speeds of approximately 5 mm/s tuned to yield thin and continuous traces of graphene ink with minimal satellite droplets on the substrate.

A method of fabrication of graphene-based circuits on a substrate comprising:

• a. preparing a printable ink comprising graphene or graphene oxide exfoliated from graphite from a bulk synthesis process or otherwise fabricating a graphene-based circuit on a substrate using said printable ink;
• and
• b. creating the graphene-based circuits by additive printing of the printable ink by direct additive manufacturing without stenciling or photolithography, wherein the additive printing is by aerosol jet printing comprising:
• i. no contact with 1-5 mm variable standoff from the substrate;
• ii. a tightly focused continuous stream of ink with 1-5 micron droplets of a viscosity between 1-1,000 cP;
• iii. printer parameters to aerosol jet print thin and continuous graphene ink with minimal satellite droplets comprising:
• sheath flow rates of 40-60 sccm,
• carrier flow rates of 15-45 sccm, and
• printing speeds of approximately 5 mm/s tuned to yield thin and continuous traces of graphene ink with minimal satellite droplets on the substrate.