Aerosol jet printed flexible graphene circuits for electrochemical sensing and biosensing
Inventors
Claussen, Jonathan • Parate, Kshama • Hersam, Mark C. • Rangnekar, Sonal V.
Assignees
Iowa State University Research Foundation Inc ISURF • Northwestern University
Publication Number
US-12306132-B2
Publication Date
2025-05-20
Expiration Date
2041-01-14
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Abstract
Methods and systems of fabrication of high resolution, high-throughput electrochemical sensing circuits on a substrate. High resolution electrochemical sensing circuits are printed by an effective additive technique to the substrate. Optionally, post-print annealing converts electrochemically inactive printed graphene into one that is electrochemically active. The printing can be by aerosol jet printing, but is not necessarily limited thereto. An example is inkjet printing and then the post-print annealing. Ink formulation would be adjusted for effectiveness with inkjet printing. Optionally biorecognition agents can be covalently bonded to the printed graphene for the purpose of electrochemical biosensing. High throughput fabrication of high-resolution graphene circuits (feature sizes in the tens of microns <50 μm) for electrochemical biosensing is possible by chemical functionalization of the graphene surface with a biological agent.
Core Innovation
The invention provides methods and systems for fabricating high resolution, high-throughput electrochemical sensing circuits on a substrate, specifically through the additive printing of graphene-based inks. The inventive process utilizes aerosol jet printing or similar additive techniques to deposit pristine graphene flakes, exfoliated from graphite, onto a variety of substrates, including flexible and rigid materials. The graphene ink can be formulated with graphene-nitrocellulose powders dispersed in a cosolvent system, allowing stable and scalable ink suitable for high-precision circuit fabrication with feature sizes in the tens of microns.
The key problem addressed by the invention is the limitation of conventional graphene printing methods, such as screen and inkjet printing, which are constrained by ink viscosity requirements, particle sizes, and large as-printed line widths (often exceeding 100 microns), thereby impeding the performance and scalability of printed electrochemical biosensors. Traditional methods for producing graphene, including mechanical exfoliation and chemical vapor deposition, are not scalable due to low yield and high energy costs, inhibiting mass adoption for disposable, point-of-care diagnostics.
A particularly novel aspect is the optional post-print annealing step, such as CO2 annealing, which converts the electrochemically inactive printed graphene into an electrochemically active material suitable for both electrochemical sensing and biosensing. This annealing process increases the oxygen-containing functional groups on the graphene surface, enabling covalent binding of biorecognition agents (such as antibodies) for selective detection of chemical or biological analytes. The invention thus enables high-throughput, cost-effective, and scalable production of high-performance, flexible, and disposable graphene-based circuits for diverse electrochemical sensing and biosensing applications.
Claims Coverage
The patent contains multiple independent claims that cover key inventive features related to the formulation, additive printing, post-processing, and application of high-resolution graphene-based circuits for sensing and biosensing applications.
Additive fabrication of high-resolution graphene-based circuits via aerosol jet printing without stenciling or photolithography
A method for fabricating graphene-based circuits on a substrate by: - Preparing a printable ink of pristine graphene flakes or graphene oxide exfoliated from graphite, dispersed in an ethyl lactate:dibutyl phthalate cosolvent system (with viscosity 1–1,000 cP). - Aerosol jet printing patterns in one or more passes on a substrate using this printable ink, enabling line thicknesses down to sub-100 nm and line widths down to sub-100 μm, without requiring stenciling, photolithography, or pre- or post-patterning steps. - The process is scalable and suitable for high-throughput direct-write additive manufacturing.
Post-print annealing to convert printed graphene into electrochemically active material
A method further comprising a post-print annealing step, such as CO2 annealing, which converts the electrochemically inactive printed graphene into an electrochemically active state. This enables the resulting printed circuit to function as an electrochemical sensor.
Post-print annealing for covalent binding of biorecognition agents to printed graphene
A method further comprising post-print annealing that increases oxygen species on the graphene surface, making it suitable for covalently binding biorecognition agents (such as antibodies) to printed graphene. This enables the use of the circuits for electrochemical biosensing.
Scalable additive manufacturing and roll-to-roll processing compatibility
The method is compatible with scalable, high-throughput additive manufacturing approaches, including roll-to-roll processing.
Application to electrochemical biosensing and immunosensing
The method and circuits fabricated are used for electrochemical sensing, including biosensing and immunosensing, such as: - Detection of biomarkers (e.g., IL-10 and IFN-gamma in actual bovine samples) within a sensing range (e.g., 0.1–10 ng/mL). - Providing biosensing without the need for additional redox probes or fluorescent labeling.
Precise aerosol jet printing parameters and ink formulations
Specifies: - Use of a printable ink comprising graphene-nitrocellulose powder, filtered through a 3.1 μm filter, with 30 mg/mL solids loading. - Aerosol jet printing features: non-contact deposition (1–5 mm standoff), 1–5 micron droplet size, ink viscosity 1–1,000 cP, and printer parameter ranges: sheath flow 40–60 sccm, carrier flow 15–45 sccm, print speed ~5 mm/s, ensuring minimal satellite droplets and high definition.
Substrate flexibility and device versatility
The method supports fabrication on various substrates, including both rigid and flexible materials, widening the range of potential sensor device platforms.
Overall, the claims broadly cover the creation of high-resolution, scalable, and versatile graphene-based circuits using direct-write additive printing, including unique ink formulations, specified printing conditions, and essential post-print annealing steps for creating electrochemically active and chemically functionalized biosensor devices, applicable to a broad set of diagnostic, sensing, and flexible electronic technologies.
Stated Advantages
Enables scalable, cost-effective manufacturing of high-performance printed graphene immunosensors suitable for disposable use.
Aerosol jet printing produces line widths as small as 10 microns and is compatible with a wide range of ink viscosities and particle sizes, allowing highly sensitive and selective biosensors.
Post-print CO2 annealing converts electrochemically inactive graphene to active material, enabling both electrochemical sensing and biosensing without metal nanoparticles or pre-labeling steps.
The fabricated sensors are flexible and robust, retaining electrical conductivity and biosensing capability after repeated bending cycles.
Printed graphene circuits can achieve feature sizes in the tens of microns (<50 μm) without lithography, improving spatial resolution and signal strength for interdigitated electrodes.
No requirement for preconcentration or labeling steps simplifies biosensor operation and lowers costs, making the devices amenable to point-of-care and disposable applications.
Metal-free, high-resolution printed graphene circuits with enhanced electronic properties and covalent biofunctionalization compatibility.
Documented Applications
Electrochemical sensing circuits, including biosensors for point-of-care diagnostics.
Immunosensors for detecting cytokines such as IL-10 and IFN-gamma in bovine samples, relevant for early detection of diseases like Johne's disease in cattle.
Histamine sensors for food safety monitoring, specifically in fish broth samples to detect toxicologically relevant histamine concentrations.
Wearable biosensors, including flexible devices for health monitoring or curvilinear biological environments.
Environmental toxin detection.
Foodborne pathogen detection.
Multiplexed sensor arrays for detection of multiple analytes in a single test solution.
Flexible and disposable printed electronic devices.
High-resolution electrical circuits such as interdigitated electrodes for sensor and biosensor applications.
Energy harvesting, electrochemical supercapacitors, and biofuel/microbial fuel cells.
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