An official website of the United States government
We have explored the potential of poly(dopamine) (PDA) thin films as versatile, high resolution conformal photoresists, using catalytic photoreduction of silver ions to micropattern the film. The combination of photosensitivity, biocompatibilty, and straightforward deposition under mild conditions into thin (~45 nm) conformal coatings on nearly any material makes PDA films of interest in lithographic patterning on highly non-planar geometries as well as on soft and biological materials where standard photoresists cannot be used. PDA and poly(norepinephrine) (PNE) films deposited with a standard autoxidation process were investigated along with PDA film deposited with a fast oxidation (FO) technique. Notably, we find that non-specific deposition of silver off the lithographic pattern is strongly suppressed in PNE and nearly absent in FO-PDA films, which makes very high contrast lithography possible. We attribute this to a lower ratio of catechol to quinone moieties in these films compared to standard PDA films. PNE and FO-PDA films exhibit smaller silver grain sizes (<40 nm) compared to standard PDA films, where grains are up to 200 nm in size. We demonstrate laser-scanning lithography patterns at 1.7 \um spatial resolution, near the optical resolution limit of the experiment. Continuous silver films can readily be deposited on PDA, PNE, and FO-PDA with blue (\lambda = 473 nm) and UV-A (375 nm) light, but not with green (515 nm) light. The UV light at lower intensities deposits silver several times faster than the blue light, but also degrades the deposited silver at high light intensities. Silver films deposited in this way reach the percolation threshold at optical doses (at \lambda = 473}nm) in the range of 10-50 kJ/cm^2 and SEM images of the films appear nearly pinhole free at comparable doses.
more »
« less
Structural color printing via polymer-assisted photochemical deposition
Abstract Structural color printings have broad applications due to their advantages of long-term sustainability, eco-friendly manufacturing, and ultra-high resolution. However, most of them require costly and time-consuming fabrication processes from nanolithography to vacuum deposition and etching. Here, we demonstrate a new color printing technology based on polymer-assisted photochemical metal deposition (PPD), a room temperature, ambient, and additive manufacturing process without requiring heating, vacuum deposition or etching. The PPD-printed silver films comprise densely aggregated silver nanoparticles filled with a small amount (estimated <20% volume) of polymers, producing a smooth surface (roughness 2.5 nm) even better than vacuum-deposited silver films (roughness 2.8 nm) at ~4 nm thickness. Further, the printed composite films have a much larger effective refractive index n (~1.90) and a smaller extinction coefficient k (~0.92) than PVD ones in the visible wavelength range (400 to 800 nm), therefore modulating the surface reflection and the phase accumulation. The capability of PPD in printing both ultra-thin (~5 nm) composite films and highly reflective thicker film greatly benefit the design and construction of multilayered Fabry–Perot (FP) cavity structures to exhibit vivid and saturated colors. We demonstrated programmed printing of complex pictures of different color schemes at a high spatial resolution of ~6.5 μm by three-dimensionally modulating the top composite film geometries and dielectric spacer thicknesses (75 to 200 nm). Finally, PPD-based color picture printing is demonstrated on a wide range of substrates, including glass, PDMS, and plastic, proving its broad potential in future applications from security labeling to color displays.
more »
« less
- PAR ID:
- 10338855
- Date Published:
- Journal Name:
- Light: Science & Applications
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 2047-7538
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract As an alternative to traditional photolithography, printing processes are widely explored for the patterning of customizable devices. However, to date, the majority of high‐resolution printing processes for functional nanomaterials are additive in nature. To complement additive printing, there is a need for subtractive processes, where the printed ink results in material removal, rather than addition. In this study, a new subtractive patterning approach that uses electrohydrodynamic‐jet (e‐jet) printing of acid‐based inks to etch nanoscale zinc oxide (ZnO) thin films deposited using atomic layer deposition (ALD) is introduced. By tuning the printing parameters, the depth and linewidth of the subtracted features can be tuned, with a minimum linewidth of 11 µm and a tunable channel depth with ≈5 nm resolution. Furthermore, by tuning the ink composition, the volatility and viscosity of the ink can be adjusted, resulting in variable spreading and dissolution dynamics at the solution/film interface. In the future, acid‐based subtractive patterning using e‐jet printing can be used for rapid prototyping or customizable manufacturing of functional devices on a range of substrates with nanoscale precision.more » « less
-
Additive manufacturing capable of controlling and dynamically modulating structures down to the nanoscopic scale remains challenging. By marrying additive manufacturing with self-assembly, we develop a UV (ultra-violet)-assisted direct ink write approach for on-the-fly modulation of structural color by programming the assembly kinetics through photo-cross-linking. We design a photo-cross-linkable bottlebrush block copolymer solution as a printing ink that exhibits vibrant structural color (i.e., photonic properties) due to the nanoscopic lamellar structures formed post extrusion. By dynamically modulating UV-light irradiance during printing, we can program the color of the printed material to access a broad spectrum of visible light with a single ink while also creating color gradients not previously possible. We unveil the mechanism of this approach using a combination of coarse-grained simulations, rheological measurements, and structural characterizations. Central to the assembly mechanism is the matching of the cross-linking timescale with the assembly timescale, which leads to kinetic trapping of the assembly process that evolves structural color from blue to red driven by solvent evaporation. This strategy of integrating cross-linking chemistry and out-of-equilibrium processing opens an avenue for spatiotemporal control of self-assembled nanostructures during additive manufacturing.more » « less
-
Abstract Direct write Inkjet Printing is a versatile additive manufacturing technology that allows for the fabrication of multiscale structures with dimensions spanning from nano to cm scale. This is made possible due to the development of novel dispensing tools, enabling controlled and precise deposition of fluid with a wide range of viscosities (1 – 50 000 mPas) in nanoliter volumes. As a result, Inkjet printing has been recognized as a potential low-cost alternative for several established manufacturing methods, including cleanroom fabrication. In this paper, we present a characterization study of PEDOT: PSS polymer ink deposition printing process realized with the help of an automated, custom Direct Write Inkjet system. PEDOT: PSS is a highly conductive ink that possesses good film forming capabilities. Applications thus include printing thin films on flexible substrates for tactile (touch) sensors. We applied the Taguchi Design of Experiment (DOE) method to produce the optimal set of PEDOT:PSS ink dispensing parameters, to study their influence on the resulting ink droplet diameter. We experimentally determined that the desired outcome of a printed thin film with minimum thickness is directly related to 1) the minimum volume of dispensed fluid and 2) the presence of a preprocessing step, namely air plasma treatment of the Kapton substrate. Results show that an ink deposit with a minimum diameter of 482 μm, and a thin film with approximately 300 nm thickness were produced with good repeatability.more » « less
-
Direct write Inkjet Printing is a versatile additive manufacturing technology that allows for the fabrication of multiscale structures with dimensions spanning from nano to cm scale. This is made possible due to the development of novel dispensing tools, enabling controlled and precise deposition of fluid with a wide range of viscosities (1 – 50 000 mPas) in nano-liter volumes. As a result, Inkjet printing has been recognized as a potential low-cost alternative for several established manufacturing methods, including cleanroom fabrication. In this paper, we present a characterization study of PEDOT: PSS polymer ink deposition printing process realized with the help of an automated, custom Direct Write Inkjet system. PEDOT: PSS is a highly conductive ink that possesses good film forming capabilities. Applications thus include printing thin films on flexible substrates for tactile (touch) sensors. We applied the Taguchi Design of Experiment (DOE) method to produce the optimal set of PEDOT:PSS ink dispensing parameters, to study their influence on the resulting ink droplet diameter. We experimentally determined that the desired outcome of a printed thin film with minimum thickness is directly related to 1) the minimum volume of dispensed fluid and 2) the presence of a preprocessing step, namely air plasma treatment of the Kapton substrate. Results show that an ink deposit with a minimum diameter of 482 μm, and a thin film with approximately 300 nm thickness were produced with good repeatability.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41377-022-00776-x
