Origami-Inspired Approaches for Biomedical Applications

Bio-Inspired Dynamically Morphing Microelectronics toward High-Density Energy Applications and Intelligent Biomedical Implants

Choreographing the adaptive shapes of patterned surfaces to exhibit designable mechanical interactions with their environment remains an intricate challenge. Here, a novel category of strain-engineered dynamic-shape materials, empowering diverse multi-dimensional shape modulations that are combined to form fine-grained adaptive microarchitectures is introduced. Using micro-origami tessellation technology, heterogeneous materials are provided with strategic creases featuring stimuli-responsive micro-hinges that morph precisely upon chemical and electrical cues. Freestanding multifaceted foldable packages, auxetic mesosurfaces, and morphable cages are three of the forms demonstrated herein of these complex 4-dimensional (4D) metamaterials. These systems are integrated in dual proof-of-concept bioelectronic demonstrations: a soft foldable supercapacitor enhancing its power density (≈108 mW cm-2), and a bio-adaptive device with a dynamic shape that may enable novel smart-implant technologies. This work demonstrates that intelligent material systems are now ready to support ultra-flexible 4D microelectronics, which can impart autonomy to devices culminating in the tangible realization of microelectronic morphogenesis.

Flexible, Biodegradable, and Wireless Magnetoelectric Paper for Simple In Situ Personalization of Bioelectric Implants

Bioelectronic implants delivering electrical stimulation offer an attractive alternative to traditional pharmaceuticals in electrotherapy. However, achieving simple, rapid, and cost-effective personalization of these implants for customized treatment in unique clinical and physical scenarios presents a substantial challenge. This challenge is further compounded by the need to ensure safety and minimal invasiveness, requiring essential attributes such as flexibility, biocompatibility, lightness, biodegradability, and wireless stimulation capability. Here, a flexible, biodegradable bioelectronic paper with homogeneously distributed wireless stimulation functionality for simple personalization of bioelectronic implants is introduced. The bioelectronic paper synergistically combines i) lead-free magnetoelectric nanoparticles (MENs) that facilitate electrical stimulation in response to external magnetic field and ii) flexible and biodegradable nanofibers (NFs) that enable localization of MENs for high-selectivity stimulation, oxygen/nutrient permeation, cell orientation modulation, and biodegradation rate control. The effectiveness of wireless electrical stimulation in vitro through enhanced neuronal differentiation of neuron-like PC12 cells and the controllability of their microstructural orientation are shown. Also, scalability, design flexibility, and rapid customizability of the bioelectronic paper are shown by creating various 3D macrostructures using simple paper crafting techniques such as cutting and folding. This platform holds promise for simple and rapid personalization of temporary bioelectronic implants for minimally invasive wireless stimulation therapies.

Origami Polyhedra-Based Soft Multicellular Robots

The reconfigurable and modular method, and the adaptive morphology method are two main methodologies to achieve the multimodal robots. Basically, the former method mimics the biological multicellular systems, while the latter is mostly inspired by the multimodal animals. Herein inspired by the rhombic dodecahedron (RDD) origami model, a novel type of soft multicellular robots with multimodal locomotion is presented. Morphologically, the combinable and expandable three-dimensional (3D)-printed soft RDD cells are assembled into several typical patterns: in-line, cross shaped, oblong shaped, and parallelogra shaped. The kinematics based on the sequential monolithic deformations of soft RDDs is analyzed to generate multimodal locomotion: peristaltic crawling, two-anchor crawling, crawling with turning functions, and omnidirectional crawling through the propagating waves in two orthogonal directions. More encouragingly, without reorganizing the pattern or reshaping the morph, the in-line multicellular robots manifest excellent climbing abilities, where the built-in rhombic meshes alternately tighten and loosen the pole-like structures to provide the gripping forces reliably without sacrificing mobility. To wrap up, owing to the monolithic and hierarchical deformability, high reconfigurability, and 3D-printable manufacturability of the RDD, we anticipate that the soft multicellular robot can potentially manifest further contributions to the advanced robotics with embodied intelligence, such as task-oriented self-assembly robots, self-reconfigurable robotic systems, and goal-directed metamorphosis robots.

Optoelectronic control of cardiac rhythm: Toward shock-free ambulatory cardioversion of atrial fibrillation

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia, progressive in nature, and known to have a negative impact on mortality, morbidity, and quality of life. Patients requiring acute termination of AF to restore sinus rhythm are subjected to electrical cardioversion, which requires sedation and therefore hospitalization due to pain resulting from the electrical shocks. However, considering the progressive nature of AF and its detrimental effects, there is a clear need for acute out-of-hospital (i.e., ambulatory) cardioversion of AF. In the search for shock-free cardioversion methods to realize such ambulatory therapy, a method referred to as optogenetics has been put forward. Optogenetics enables optical control over the electrical activity of cardiomyocytes by targeted expression of light-activated ion channels or pumps and may therefore serve as a means for cardioversion. First proof-of-principle for such light-induced cardioversion came from in vitro studies, proving optogenetic AF termination to be very effective. Later, these results were confirmed in various rodent models of AF using different transgenes, illumination methods, and protocols, whereas computational studies in the human heart provided additional translational insight. Based on these results and fueled by recent advances in molecular biology, gene therapy, and optoelectronic engineering, a basis is now being formed to explore clinical translations of optoelectronic control of cardiac rhythm. In this review, we discuss the current literature regarding optogenetic cardioversion of AF to restore normal rhythm in a shock-free manner. Moreover, key translational steps will be discussed, both from a biological and technological point of view, to outline a path toward realizing acute shock-free ambulatory termination of AF.

Origamic metal-organic framework toward mechanical metamaterial

Origami, known as paper folding has become a fascinating research topic recently. Origami-inspired materials often establish mechanical properties that are difficult to achieve in conventional materials. However, the materials based on origami tessellation at the molecular level have been significantly underexplored. Herein, we report a two-dimensional (2D) porphyrinic metal-organic framework (MOF), self-assembled from Zn nodes and flexible porphyrin linkers, displaying folding motions based on origami tessellation. A combined experimental and theoretical investigation demonstrated the origami mechanism of the 2D porphyrinic MOF, whereby the flexible linker acts as a pivoting point. The discovery of the 2D tessellation hidden in the 2D MOF unveils origami mechanics at the molecular level.

A Magnetic Bio-Inspired Soft Carrier as a Temperature-Controlled Gastrointestinal Drug Delivery System

Currently, gastrointestinal bleeding in the colon wall and the small bowel is diagnosed and treated with endoscopes. However, the locations of this condition are often problematic to treat using traditional flexible and tethered tools. New studies commonly consider untethered devices for solving this problem. However, there still exists a gap in the extant literature, and more research is needed to diagnose and deliver drugs in the lower gastrointestinal tract using soft robotic carriers. This paper discusses the development of an untethered, magnetically-responsive bio-inspired soft carrier. A molding process is utilized to produce prototypes from Diisopropylidene-1,6-diphenyl-1,6-hexanediol-based Polymer with Ethylene Glycol Dimethacrylate (DiAPLEX) MP-3510 - a shape memory polymer with a low transition temperature to enable the fabrication of these carriers. The soft carrier design is validated through simulation results of deformation caused by magnetic elements embedded in the carrier in response to an external field. The thermal responsiveness of the fabricated prototype carriers is assessed ex vivo and in a phantom. The results indicate a feasible design capable of administering drugs to a target inside a phantom of a large intestine. The soft carrier introduces a method for the controlled release of drugs by utilizing the rubbery modulus of the polymer and increasing the recovery force through magnetic actuation.

Kirigami-Origami-Inspired Lead-Free Piezoelectric Ceramics

Kirigami- and oirigami-inspired techniques have emerged as effective strategies for material structure design; however, the use of these techniques is usually limited to soft and deformable materials. Piezoelectric ceramics, which are typical functional ceramics, are widely used in electronic and energy devices; however, the processing options for piezoelectric ceramics are limited by their brittleness and feedstock viscosity. Here, a design strategy is proposed for the preparation of lead-free piezoelectric ceramics inspired by kirigami/origami. This strategy involves direct writing printing and control over the external gravity during the calcination process for the preparation of curved and porous piezoelectric ceramics with specific shapes. The sintered BaTiO₃ ceramics with curved geometries produced using this strategy exhibit a high piezoelectric constant (d₃₃ = 275 pC N^-1 ), which is 45% higher than that of conventionally sintered sheet ceramics. The curved structure of the ceramics is well-suited for use in the human body and it was determined that these curved ceramics can detect pulse signals. This strategy can be applied in the large-scale and low-cost production of other piezoelectric ceramics with various curved shapes and provides a new approach for the preparation of complex-shaped ceramics.

Emerging biomaterials and technologies to control stem cell fate and patterning in engineered 3D tissues and organoids

The ability to create complex three-dimensional cellular models that can effectively replicate the structure and function of human organs and tissues in vitro has the potential to revolutionize medicine. Such models could facilitate the interrogation of developmental and disease processes underpinning fundamental discovery science, vastly accelerate drug development and screening, or even be used to create tissues for implantation into the body. Realization of this potential, however, requires the recreation of complex biochemical, biophysical, and cellular patterns of 3D tissues and remains a key challenge in the field. Recent advances are being driven by improved knowledge of tissue morphogenesis and architecture and technological developments in bioengineering and materials science that can create the multidimensional and dynamic systems required to produce complex tissue microenvironments. In this article, we discuss challenges for in vitro models of tissues and organs and summarize the current state-of-the art in biomaterials and bioengineered systems that aim to address these challenges. This includes both top-down technologies, such as 3D photopatterning, magnetism, acoustic forces, and cell origami, as well as bottom-up patterning using 3D bioprinting, microfluidics, cell sheet technology, or composite scaffolds. We illustrate the varying ways that these can be applied to suit the needs of different tissues and applications by focussing on specific examples of patterning the bone-tendon interface, kidney organoids, and brain cancer models. Finally, we discuss the challenges and future prospects in applying materials science and bioengineering to develop high-quality 3D tissue structures for in vitro studies.

4D Multiscale Origami Soft Robots: A Review

Time-dependent shape-transferable soft robots are important for various intelligent applications in flexible electronics and bionics. Four-dimensional (4D) shape changes can offer versatile functional advantages during operations to soft robots that respond to external environmental stimuli, including heat, pH, light, electric, or pneumatic triggers. This review investigates the current advances in multiscale soft robots that can display 4D shape transformations. This review first focuses on material selection to demonstrate 4D origami-driven shape transformations. Second, this review investigates versatile fabrication strategies to form the 4D mechanical structures of soft robots. Third, this review surveys the folding, rolling, bending, and wrinkling mechanisms of soft robots during operation. Fourth, this review highlights the diverse applications of 4D origami-driven soft robots in actuators, sensors, and bionics. Finally, perspectives on future directions and challenges in the development of intelligent soft robots in real operational environments are discussed.

The role of biomaterials and scaffolds in immune responses in regenerative medicine: macrophage phenotype modulation by biomaterial properties and scaffold architectures

Scaffolds are an integral part of the regenerative medicine field. The contact of biomaterials with tissue, as was clearly observed over the years, induces immune reactions in a material and patient specific manner, where both surface and bulk properties of scaffolds, together with their 3D architecture, have a significant influence on the outcome. This review presents an overview of the reactions to the biomaterials with a specific focus on clinical complications with the implants in the context of immune reactions and an overview of the studies involving biomaterial properties and interactions with innate immune system cells. We emphasize the impact of these studies on scaffold selection and upscaling of microenvironments created by biomaterials from 2D to 3D using immune cell encapsulation, seeding in a 3D scaffold and co-culture with relevant tissue cells. 3D microenvironments are covered with a specific focus on innate cells since a large proportion of these studies used innate immune cells. Finally, the recent studies on the incorporation of adaptive immune cells in immunomodulatory systems are covered in this review. Biomaterial-immune cell interactions are a critical part of regenerative medicine applications. Current efforts in establishing the ground rules for such interactions following implantation can control immune response during all phases of inflammation. Thus, in the near future for complete functional recovery, tissue engineering and control over biomaterials must be considered at the first step of immune modulation and this review covers these interactions, which have remained elusive up to now.

Fabrication of Highly Interconnected Poly(ε-caprolactone)/cellulose Nanofiber Composite Foams by Microcellular Foaming and Leaching Processes

In this study, microcellular polycaprolactone (PCL)/sodium bicarbonate (NaHCO₃)/cellulose nanofiber (CNF) composite foams with highly interconnected porous structures were successfully fabricated by microcellular foaming and particle leaching processes. Supercritical CO₂ (scCO₂) served as a physical foaming agent, NaHCO₃ was chosen as a chemical foaming agent and porogen, and CNF acted as a heterogeneous nucleating agent. The effect of scCO₂, NaHCO₃, and CNF on pore structures and the cofoaming mechanism were investigated. The results indicated that the addition of NaHCO₃ and CNF increased the melt strength of the PCL matrix significantly. During the foaming process, the presence of CNF can form a rigid network due to the hydrogen bonding or mechanical entanglement between individual nanofibers, improving the nucleating efficiency but slowing down the cell growth rate. Additionally, due to the interaction of "soft" PCL matrix and "hard" domains in a PCL-based composite during the foaming process, together with the NaHCO₃ leaching process, highly interconnected cell structures appeared. The obtained PCL/NaHCO₃/CNF composite foams had a cell size of 15.8 μm and cell density of 6.3 × 10⁷ cells/cm³, as well as an open-cell content of 82%. The reported strategy in this paper may provide the guidelines and data supports for the fabrication of a PCL-based porous scaffold.

Stretchable origami robotic arm with omnidirectional bending and twisting

Inspired by the embodied intelligence observed in octopus arms, we introduce magnetically controlled origami robotic arms based on Kresling patterns for multimodal deformations, including stretching, folding, omnidirectional bending, and twisting. The highly integrated motion of the robotic arms is attributed to inherent features of the reconfigurable Kresling unit, whose controllable bistable deploying/folding and omnidirectional bending are achieved through precise magnetic actuation. We investigate single- and multiple-unit robotic systems, the latter exhibiting higher biomimetic resemblance to octopus' arms. We start from the single Kresling unit to delineate the working mechanism of the magnetic actuation for deploying/folding and bending. The two-unit Kresling assembly demonstrates the basic integrated motion that combines omnidirectional bending with deploying. The four-unit Kresling assembly constitutes a robotic arm with a larger omnidirectional bending angle and stretchability. With the foundation of the basic integrated motion, scalability of Kresling assemblies is demonstrated through distributed magnetic actuation of double-digit number of units, which enables robotic arms with sophisticated motions, such as continuous stretching and contracting, reconfigurable bending, and multiaxis twisting. Such complex motions allow for functions mimicking octopus arms that grasp and manipulate objects. The Kresling robotic arm with noncontact actuation provides a distinctive mechanism for applications that require synergistic robotic motions for navigation, sensing, and interaction with objects in environments with limited or constrained access. Based on small-scale Kresling robotic arms, miniaturized medical devices, such as tubes and catheters, can be developed in conjunction with endoscopy, intubation, and catheterization procedures using functionalities of object manipulation and motion under remote control.