Bubble-blowing-inspired sub-micron thick freestanding silk films for programmable electronics.

Area of Science:

• Materials Science
• Biomaterials Engineering
• Nanotechnology

Background:

• Thin film electronics are crucial for wearable devices, but fabricating freestanding, sub-micron thick films, especially from materials like silk protein, remains challenging.
• Existing methods often lack simplicity or struggle with materials exhibiting metastable conformations.

Purpose of the Study:

• To develop a facile method for producing sub-micron thick freestanding silk films.
• To explore the properties and potential applications of these novel silk films in electronics.

Main Methods:

• A dip-coating technique inspired by soap bubble formation was employed using a closed-loop frame and concentrated silk fibroin solution.
• Solvent evaporation was used to obtain substrate-free silk films with controlled thickness and smooth surfaces.

Main Results:

• Sub-micron thick (∼150 nm) freestanding silk films with extremely smooth surfaces (Rq < 3 nm) were successfully fabricated.
• The films demonstrated high adaptability and could conformally attach to nonplanar surfaces like wrinkled skin and human hair.
• Demonstrated applications include transient/durable circuits, skin electrodes, light-emitting devices, and injectable electronics.

Conclusions:

• The dip-coating method offers a new, simple approach for preparing freestanding thin polymer films.
• The ultra-thin silk films exhibit promising properties for advanced thin film electronics in wearable and biomedical fields.