Edible Origami Actuators Using Gelatin-Based Bioplastics

Abstract

The potential of ingestible medical devices can be greatly enhanced through the use of smart structures made from stimuli-responsive materials. While hydration is a convenient stimulus for inducing shape changes in biomaterials, finding robust materials that can achieve rapid actuation, facile manufacturability, and biocompatibility suitable for ingestible medical devices poses practical challenges. Hydration is a convenient stimulus to induce shape changes in smart biomaterials; however, there are many practical challenges to identifying materials that can achieve rapid actuation and facile manufacturability while satisfying constraints associated with biocompatibility requirements and mechanical properties that are suitable for ingestible medical devices. Herein, we illustrate the formulation and processability of a moistureresponsive genipin-crosslinked gelatin bioplastic system, which can be processed into complex three-dimensional shapes. Mechanical characterization of bioplastic samples showed Young's Modulus values as high as 1845 MPa and toughness values up to 52 MJ/m 3 , using only food-safe ingredients. Custom molds and UV-laser processing enabled the fabrication of centimeter-scale structures with over 150 independent actuating joints. These self-actuating structures soften and unfold in response to surrounding moisture, eliminating the need for additional stimuli or actuating elements.

Dynamic, Viscoelasticity-Driven Shape Change of Elastomer Bilayers

“…The polymer layers are typically hydrogels where the active layer swells more than the passive layer resulting in bending toward the passive layer. The swelling can be solvent (i.e., water)-, temperature-, pH-, electric-field- or ionic strength-induced. − Folding into more sophisticated final shapes can be achieved via photopatterning, lithography, or 3D printing (for 4D printing). − Seedpod-like twisting has also been mimicked by imparting orientational order into polymer and elastomeric bilayers to generate solvent − - or temperature − -induced twisting, as well as pH-, ionic strength-, and light-induced shape change. Some highly engineered materials can respond to multiple stimuli such as temperature and solvent, photothermal or electro-thermal, and UV light, NIR, solar, and heat .…”

Regeneration and Long-Term Stability of a Low-Power Eco-Friendly Temperature Sensor Based on a Hydrogel Nanocomposite

“…Gelatin, a biodegradable polymer obtained from collagen hydrolysis, forms hydrogels with enhanced dielectric and mechanical properties due to its ability to trap liquid molecules and fillers [20,24,25]. The prevalence of polar functional groups in the gelatin hydrogel facilitates the development of various applications, including actuators [26][27][28][29], sensors [10,[30][31][32], and organic transistors [33][34][35].…”