Aerosol Jet Printing of Phase-Inversion Graphene Inks for High-Aspect-Ratio Printed Electronics and Sensors

Aerosol jet printing is a technology particularly suited for additive manufacturing of functional microstructures, offering resolutions as high as 10 μm, broad compatibility for electronic nanomaterials, and noncontact deposition, making it compelling for device prototyping and conformal printing. To adapt this method from thin film patterns to taller features, both ink rheology and drying kinetics require careful engineering. Printing in a solvent-rich, low-viscosity state commonly results in a puddle, with liquid-phase spreading and susceptibility to instabilities, whereas printing solvent-depleted aerosol results in a granular morphology with high overspray. Here, we demonstrate a strategy to mitigate this trade-off by tailoring the evolution of ink rheology during the process, using a graphene ink containing the nonsolvent glycerol as an exemplar. During droplet transport to the nozzle, evaporation of volatile primary solvents increases the glycerol concentration, resulting in gel formation. This switch in the ink rheology between the cartridge and substrate maintains the print resolution at high deposition rates. Moreover, multiple layers can be printed in rapid succession to build up high aspect ratio microstructures, as demonstrated by continuously printed cylindrical pillars with diameters on the order of ∼100 μm and aspect ratios as high as ∼10. Finally, the efficacy of this ink formulation strategy for a CuO nanoparticle ink confirms the generalizability of this strategy for a broader scope of colloidal nanomaterial inks. In addition to its utility for microscale additive manufacturing of 2.5D structures, this strategy provides insights into higher deposition rate patterning to improve scalability and throughput of aerosol jet printing

Aerosol Jet Printing of Phase-Inversion Graphene Inks for High-Aspect-Ratio Printed Electronics and Sensors

Aerosol jet printing is a technology particularly suited for additive manufacturing of functional microstructures, offering resolutions as high as 10 μm, broad compatibility for electronic nanomaterials, and noncontact deposition, making it compelling for device prototyping and conformal printing. To adapt this method from thin film patterns to taller features, both ink rheology and drying kinetics require careful engineering. Printing in a solvent-rich, low-viscosity state commonly results in a puddle, with liquid-phase spreading and susceptibility to instabilities, whereas printing solvent-depleted aerosol results in a granular morphology with high overspray. Here, we demonstrate a strategy to mitigate this trade-off by tailoring the evolution of ink rheology during the process, using a graphene ink containing the nonsolvent glycerol as an exemplar. During droplet transport to the nozzle, evaporation of volatile primary solvents increases the glycerol concentration, resulting in gel formation. This switch in the ink rheology between the cartridge and substrate maintains the print resolution at high deposition rates. Moreover, multiple layers can be printed in rapid succession to build up high aspect ratio microstructures, as demonstrated by continuously printed cylindrical pillars with diameters on the order of ∼100 μm and aspect ratios as high as ∼10. Finally, the efficacy of this ink formulation strategy for a CuO nanoparticle ink confirms the generalizability of this strategy for a broader scope of colloidal nanomaterial inks. In addition to its utility for microscale additive manufacturing of 2.5D structures, this strategy provides insights into higher deposition rate patterning to improve scalability and throughput of aerosol jet printing

Aerosol Jet Printing of Phase-Inversion Graphene Inks for High-Aspect-Ratio Printed Electronics and Sensors

Aerosol jet printing is a technology particularly suited for additive manufacturing of functional microstructures, offering resolutions as high as 10 μm, broad compatibility for electronic nanomaterials, and noncontact deposition, making it compelling for device prototyping and conformal printing. To adapt this method from thin film patterns to taller features, both ink rheology and drying kinetics require careful engineering. Printing in a solvent-rich, low-viscosity state commonly results in a puddle, with liquid-phase spreading and susceptibility to instabilities, whereas printing solvent-depleted aerosol results in a granular morphology with high overspray. Here, we demonstrate a strategy to mitigate this trade-off by tailoring the evolution of ink rheology during the process, using a graphene ink containing the nonsolvent glycerol as an exemplar. During droplet transport to the nozzle, evaporation of volatile primary solvents increases the glycerol concentration, resulting in gel formation. This switch in the ink rheology between the cartridge and substrate maintains the print resolution at high deposition rates. Moreover, multiple layers can be printed in rapid succession to build up high aspect ratio microstructures, as demonstrated by continuously printed cylindrical pillars with diameters on the order of ∼100 μm and aspect ratios as high as ∼10. Finally, the efficacy of this ink formulation strategy for a CuO nanoparticle ink confirms the generalizability of this strategy for a broader scope of colloidal nanomaterial inks. In addition to its utility for microscale additive manufacturing of 2.5D structures, this strategy provides insights into higher deposition rate patterning to improve scalability and throughput of aerosol jet printing

Transfer Printing of Sub‑5 μm Graphene Electrodes for Flexible Microsupercapacitors

Printed graphene microsupercapacitors (MSCs) are attractive for scalable and low-cost on-chip energy storage for distributed electronic devices. Although electronic devices have experienced significant scaling to smaller formats, the corresponding miniaturization of energy storage components has been limited, with a typical resolution of ∼30 μm for printed graphene patterns to date. Transfer printing is demonstrated here for patterning graphene electrodes with fine line and spacing resolution less than 5 μm. The resulting devices exhibit an exceptionally small footprint (∼0.0067 mm²), which provides, to the best of our knowledge, the smallest printed graphene MSCs. Despite this, the devices retain excellent performance with a high areal capacitance of ∼6.63 mF/cm² along with excellent electrochemical stability and mechanical flexibility, resulting from an efficient nonplanar electrode structure and an optimized two-step photoannealing method. As a result, this miniaturization strategy facilitates the on-chip integration of printed graphene MSCs to power emerging electronic devices

High-Resolution Transfer Printing of Graphene Lines for Fully Printed, Flexible Electronics

Pristine graphene inks show great promise for flexible printed electronics due to their high electrical conductivity and robust mechanical, chemical, and environmental stability. While traditional liquid-phase printing methods can produce graphene patterns with a resolution of ∼30 μm, more precise techniques are required for improved device performance and integration density. A high-resolution transfer printing method is developed here capable of printing conductive graphene patterns on plastic with line width and spacing as small as 3.2 and 1 μm, respectively. The core of this method lies in the design of a graphene ink and its integration with a thermally robust mold that enables annealing at up to ∼250 °C for precise, high-performance graphene patterns. These patterns exhibit excellent electrical and mechanical properties, enabling favorable operation as electrodes in fully printed electrolyte-gated transistors and inverters with stable performance even following cyclic bending to a strain of 1%. The high resolution coupled with excellent control over the line edge roughness to below 25 nm enables aggressive scaling of transistor dimensions, offering a compelling route for the scalable manufacturing of flexible nanoelectronic devices

High-Resolution Transfer Printing of Graphene Lines for Fully Printed, Flexible Electronics

Pristine graphene inks show great promise for flexible printed electronics due to their high electrical conductivity and robust mechanical, chemical, and environmental stability. While traditional liquid-phase printing methods can produce graphene patterns with a resolution of ∼30 μm, more precise techniques are required for improved device performance and integration density. A high-resolution transfer printing method is developed here capable of printing conductive graphene patterns on plastic with line width and spacing as small as 3.2 and 1 μm, respectively. The core of this method lies in the design of a graphene ink and its integration with a thermally robust mold that enables annealing at up to ∼250 °C for precise, high-performance graphene patterns. These patterns exhibit excellent electrical and mechanical properties, enabling favorable operation as electrodes in fully printed electrolyte-gated transistors and inverters with stable performance even following cyclic bending to a strain of 1%. The high resolution coupled with excellent control over the line edge roughness to below 25 nm enables aggressive scaling of transistor dimensions, offering a compelling route for the scalable manufacturing of flexible nanoelectronic devices

Direct Printing of Graphene Electrodes for High-Performance Organic Inverters

Scalable fabrication of high-resolution electrodes and interconnects is necessary to enable advanced, high-performance, printed, and flexible electronics. Here, we demonstrate the direct printing of graphene patterns with feature widths from 300 μm to ∼310 nm by liquid-bridge-mediated nanotransfer molding. This solution-based technique enables residue-free printing of graphene patterns on a variety of substrates with surface energies between ∼43 and 73 mN m^–1. Using printed graphene source and drain electrodes, high-performance organic field-effect transistors (OFETs) are fabricated with single-crystal rubrene (p-type) and fluorocarbon-substituted dicyanoperylene-3,4:9,10-bis­(dicarboximide) (PDIF-CN₂) (n-type) semiconductors. Measured mobilities range from 2.1 to 0.2 cm² V^–1 s^–1 for rubrene and from 0.6 to 0.1 cm² V^–1 s^–1 for PDIF-CN₂. Complementary inverter circuits are fabricated from these single-crystal OFETs with gains as high as ∼50. Finally, these high-resolution graphene patterns are compatible with scalable processing, offering compelling opportunities for inexpensive printed electronics with increased performance and integration density

Comprehensive Enhancement of Nanostructured Lithium-Ion Battery Cathode Materials via Conformal Graphene Dispersion

Efficient energy storage systems based on lithium-ion batteries represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Nanostructured electrode materials present compelling opportunities for high-performance lithium-ion batteries, but inherent problems related to the high surface area to volume ratios at the nanometer-scale have impeded their adoption for commercial applications. Here, we demonstrate a materials and processing platform that realizes high-performance nanostructured lithium manganese oxide (nano-LMO) spinel cathodes with conformal graphene coatings as a conductive additive. The resulting nanostructured composite cathodes concurrently resolve multiple problems that have plagued nanoparticle-based lithium-ion battery electrodes including low packing density, high additive content, and poor cycling stability. Moreover, this strategy enhances the intrinsic advantages of nano-LMO, resulting in extraordinary rate capability and low temperature performance. With 75% capacity retention at a 20C cycling rate at room temperature and nearly full capacity retention at −20 °C, this work advances lithium-ion battery technology into unprecedented regimes of operation