3D electronic and photonic structures as active biological interfaces

Abstract

Biocompatible materials and structures with three-dimensional (3D) architectures establish an ideal platform for the integration of living cells and tissues, serving as desirable interfaces between biotic and abiotic systems. While conventional 3D bioscaffolds provide a mechanical support for biomatters, emerging developments of micro-, nano-, and mesoscale electronic and photonic devices offer new paradigms in analyzing and interrogating biosystems. In this review, we summarize recent advances in the development of 3D functional biointerfaces, with a particular focus on electrically and optically active materials, devices, and structures. We first give an overview of representative methods for manufacturing 3D biointegrated structures, such as chemical synthesis, microfabrication, mechanical assembly, and 3D printing. Subsequently, exemplary 3D nano-, micro-, and mesostructures based on various materials, including semiconductors, metals, and polymers are presented. Finally, we highlight the latest progress on versatile applications of such active 3D structures in the biomedical field, like cell culturing, biosignal sensing/modulation, and tissue regeneration. We believe future 3D micro-, nano-, and mesostructures that incorporate electrical and/or optical functionalities will not only profoundly advance the fundamental studies in biological sciences, but also create enormous opportunities for medical diagnostics and therapies. K E Y W O R D S

3D Electrodes for Bioelectronics

“…One of the unique characteristics of biological signals that occur inside an organism is that they can represent a biological signal of a specific region of complex organs, e.g., the brain, that have different roles and functions depending on the region, while these signals also can indicate an early stage of disease or pain, such as myocardial infarction, caused by partial necrosis inside the organ. [16][17][18][19] Thus, with 2D bioelectrodes, including flexible and stretchable bioelectronics, it is difficult to form a complete conformal biointerface and measure biological signals in the deep regions of organisms due to the limitation of the 2D planar structure. Therefore, in order to form an interface with the internal regions of 3D-structured organisms, bioelectronic engineers attempted to fabricate 3D electrodes, such as 3D MEA for intracellular-like in vitro and in vivo…”

“…Macroscopically, most living organisms and associated biomolecules, cells, tissues, and organs have inhomogeneous and irregular 3D structures with anisotropy. [16] This section discusses the advantages of macroscopic 3D-structured bioelectrodes and the microscopic properties of 3D electrodes at the electrode-tissue interface.…”

“…Mechanically guided assembly can construct 3D structures through the structural integration with soft elastomers. [16,[177][178][179][180] In this paragraph, an overall explanation of such an assembly process in bioelectronics with various strategies based on wavy, kirigami structures, and mesh structures is discussed.…”

“…[196] To solve this problem, several researchers have tried to fabricate 3D structures for penetrating the dead cell layer in order to explore the exact extracellular and even intracellular acti vity. [16,144,[195][196][197][198] Through this ongoing research, it is possible to selectively penetrate the desired site and use 3D electrodes to detect intracellular signals.…”

“…[3][4][5][6][7][8][9][10] The electrophysiology or a 3D stimulation electrode for retinal prostheses that can be used to stimulate retinal cells inside the retina. [16,20,21,22] Herein, we present recent research regarding the biomedical application of 3D electrodes. First, we discuss how structural differences between 2D and 3D electrodes affect their functionality.…”