Rapid nano impact printing of silk biopolymer thin films

Abstract

In this paper, nano impact printing of silk biopolymer films is described. An indenter is rapidly accelerated and transfers the nanopattern from a silicon master into the silk film during an impact event that occurs in less than 1 ms. Contact stresses of greater than 100 MPa can be achieved during the short impact period with low power and inexpensive hardware. Ring shaped features with a diameter of 2 μm and a ring width of 100-200 nm were successfully transferred into untreated silk films using this method at room temperature. Mechanical modeling was carried out to determine the contact stress distribution, and demonstrates that imprinting can occur for contact stresses of less than 2 MPa. Thermal characterization at the impact location shows that raising the temperature to 70 • C has only a limited effect on pattern transfer. Contact stresses of greater than approximately 100 MPa result in excessive deformation of the film and poor pattern transfer.

Silk protein nanowires patterned using electron beam lithography

“…For instance, nanoimprinting allows for rapid generation of patterns, but requires suitable templates leading to incomplete molding during transfer steps. The process also often utilizes harsh chemicals for processing, and requires high temperature and pressures, limiting biomedical applications [15,16]. DPN and PPL enable direct write methods with a nanoscale resolutions, but are relatively slow, and often limited to simple designs [17,18].…”

Biopatterning of Silk Proteins for Soft Micro-optics

“…However, typically, these indirect methods require the formation of master patterns that can then be transferred to the biomaterial. Despite excellent resolution, limitations include the need to construct these masters and molds, loss of fidelity or incomplete molding during transfer steps, and often, high temperature and pressure requirements. , Direct printing techniques such as E-beam lithography, femtosecond laser machining, and two and three-photon interference lithography have been reported but are quite expensive. − Optically iridescent architectures have also been shown by patterning of silk films using a “breath figure approach” . Although this approach can be used to form cavities ranging from submicrometer to micrometer scales, the scalability and limitations on geometry and control of cavity size make these approaches limited.…”

“…Despite excellent resolution, limitations include the need to construct these masters and molds, loss of fidelity or incomplete molding during transfer steps, and often, high temperature and pressure requirements. 20,21 Direct printing techniques such as E-beam lithography, femtosecond laser machining, and two and three-photon interference lithography have been reported but are quite expensive. 22−26 Optically iridescent architectures have also been shown by patterning of silk films using a "breath figure approach".…”

Silk Protein Lithography as a Route to Fabricate Sericin Microarchitectures

“…Strategies such as electrospinning of fibers, and the formation of 2D film and 3D hydrogel architectures are typically employed, mostly without the ability to accurately control spatial arrangement of the protein . Patterning or micro and nanostructure fabrication via techniques including soft lithography and imprinting have not been readily translated to sericin. Further, these techniques may be constrained in the formation of intricate architectures or require mold fabrication and multiple transfer steps …”