Soft and Ion‐Conducting Materials in Bioelectronics: From Conducting Polymers to Hydrogels

Abstract

Bioelectronics devices that directly interface with cells and tissue have applications in neural and cardiac stimulation and recording, electroceuticals, and brain machine interfaces for prostheses. The interface between bioelectronic devices and biological tissue is inherently challenging due to the mismatch in both mechanical properties (hard vs soft) and charge carriers (electrons vs ions). In addition to conventional metals and silicon, new materials have bridged this interface, including conducting polymers, carbon‐based nanomaterials, as well as ion‐conducting polymers and hydrogels. This review provides an update on advances in soft bioelectronic materials for current and future therapeutic applications. Specifically, this review focuses on soft materials that can conduct both electrons and ions, and also deliver drugs and small molecules. The future opportunities and emerging challenges in the field are also highlighted.

Organic Bioelectronics for Neurotransmitter Release at the Speed of Life

“…Material selection is not only important for device performance, the choice of materials is also crucial for a successful interface between device and tissue, especially when the device is to be implantable. [10,34] For materials and devices to be fully biocompatible, their surface as well as mechanical properties must be accepted by surrounding tissues and their cells. The materials also need to endure the biological environment over the intended timeframe to maintain a stable and reliable device performance.…”

“…Due to their softer mechanical properties organic polymers can provide a more body-friendly interface compared to classic inorganic materials. [6,10] Organic polymers are widely used in medicine, for example in drug delivery applications and as coating on stents. [84] In this chapter, the materials used to fabricate iontronic devices are presented, starting with IEMs and electrode materials, followed by a description of microfabrication techniques.…”

“…[40] Another method of neurotransmitter release can be achieved using materials such as hydrogels and polymers loaded with the neurotransmitter. [6,10] Molecules loaded in a these materials can be released slowly by passive di usion. If the molecule is an ion, active release can be performed from a conducting polymer, known as electrochemical release.…”

“…Even though this can be performed very locally and in a controlled manner, an even more seamless interface would be to mimic the signaling as it occurs naturally within the biological system. [9,10] The term "animal electricity" had been around since Galvani's experiments during the 18th century. [11] This concept is still valid in the sense that xi neuronal action potentials are referred to as electrical transmission, even though the charge carriers for these action potentials are ions rather than electrons.…”

Organic Bioelectronics: Using Highly Conjugated Polymers to Interface with Biomolecules, Cells, and Tissues in the Human Body

“…[ 221,222 ] An in‐depth discussion of developments in both stretchable and degradable conjugated polymers is beyond the scope of this report, but for a full discussion we recommend a number of recent reviews in this area. [ 43,149,215,221,223,224 ]…”