Biofunctional Silk Kirigami With Engineered Properties

Abstract

The fabrication of multifunctional materials that interface with living environments is a problem of great interest. A variety of structural design concepts have been integrated with functional materials to form biodevices and surfaces for health monitoring. In particular, approaches based on kirigami-inspired cuts can engineer flexibility in materials through the creation of patterned defects. Here, the fabrication of a biodegradable and biofunctional "silk kirigami" material is demonstrated. Mechanically flexible, free-standing, optically transparent, large-area biomaterial sheets with precisely defined and computationally designed microscale cuts can be formed using a single-step photolithographic process. Using modeling techniques, it is shown how cuts can generate remarkable "self-shielding" leading to engineered elastic behavior and deformation. As composites with conducting polymers, flexible, intrinsically electroactive sheets can be formed.Importantly, the silk-kirigami sheets are biocompatible, can serve as substrates for cell culture, and be proteolytically resorbed. The unique properties of silk kirigami suggest a host of applications as transient, "green", functional biointerfaces, and flexible bioelectronics.

Emerging Silk Material Trends: Repurposing, Phase Separation and Solution-Based Designs

“…The popularity of silk continues to grow, impacting virtually all areas of biomedical research. For example, the precision cutting [68] or patterning of silks has already provided the ability to influence applications, ranging from stem cell biology to the design of rewritable optical storage devices [69]. However, in light of the ongoing Covid-19 pandemic, I have picked one example where silk is having a particular impact.…”

Kirigami‐Inspired Biodesign for Applications in Healthcare

“…Staggered linear and Y-shape cuts (15 mm and 5 mm) [60] Photoactive silk fibroin Photolithography Staggered linear cuts (25 µm), branched Y-shape cuts, saddles, chevrons [37] Graphite electrodes on polyimide sheet Laser cutting Staggered linear cuts (over 3 cm) [61] Gold nanofilms Dual-beam focused ion beam (FIB)/SEM Arcs and 3D microdomes (sub-50-nm) [27] Gold traces embedded in thin-film Parylene C Oxygen plasma etching Serpentine cuts [62] Mono-layer MoS 2 on PDMS Molding and plasma etching Linear patterns, pyramids, out-of-plane springs with alternating C-shapes [35] PMMA-PI composite Wet etching and laser cutting 2D hierarchical designs [63] PEO-PAA composite Blade cutting Curved patterns, linear cuts [64] Multiwalled boron nitride nanotubes Pressure-induced Folded nanoribbon internal structures/pleats [65] PLA-PEDOT:PSS Laser cutting Y-shape cuts [24] Hydrogel films-carboxyl-Zr 4+ metal coordination complexes Photolithography Custom papercut designs, woven-like alternating vertical/horizontal lines [30] Graphene sandwiched between polyimide sheets Photolithography and reactive ion etching Mesh (islands connected by kirigami bridges) [66] Liquid crystal elastomer Two-photon polymerization (2PP) Linear cuts, hinged squares, [67] PET encapsulated in PDMS Laser cutting Graded kirigami (10 mm segments of increasing void area) [68] PVDF-TrFE composite (ZnO nanoparticles and MWCNTs)…”

“…Reproduced with permission. [ 37 ] Copyright 2020, American Chemical Society. e) An auxetic honeycomb (bow‐tie) architecture formed in chitosan sheets via laser ablation.…”

“…d) Y-shaped cuts in a biodegradable flexible silk sheets formed by photolithography. Reproduced with permission [37]. Copyright 2020, American Chemical Society.…”

“…Silk fibroin kirigami films (loaded with fluorescein isothiocyanate (FITC)-dextran MW 4 kDa) with adherence of C2C12 cells 7 days after seeding.Arrows indicate cytoskeletal bridges across the cuts, followed by DAPI and actin staining. Reproduced with permission [37]. Copyright 2020, American Chemical Society.…”