Monopolar and Bipolar Membranes in Organic Bioelectronic Devices

Abstract

In the 1970s it was discovered that organic polymers, a class of materials otherwise best know as insulating plastics, could be made electronically conductive. As an alternative to silicon semiconductors, organic polymers offer many novel features, characteristics, and opportunities, such as producing electronics at low costs using printing techniques, using organic chemistry to tune optical and electronic properties, and mechanical flexibility. The conducting organic polymers have been used in a vast array of devices, exemplified by organic transistors, light-emitting diodes, and solar cells. Due to their softness, biocompatibility, and combined electronic and ionic transport, organic electronic materials are also well suited as the active material in bioelectronic applications, a scientific and engineering area in which electronics interface with biology. The coupling of ions and electrons is especially interesting, as ions serve as signal carriers in all living organisms, thus offering a direct translation of electronic and ionic signals. To further enable complex control of ionic fluxes, organic electronic materials can be integrated with various ionic components, such as ion-conducting diodes and transistors.This thesis reports a background to the field of organic bioelectronic and ionic devices, and also presents the integration of ionic functions into organic bioelectronic devices. First, an electrophoretic drug delivery device is presented, capable of delivering ions at high spatiotemporal resolution. The device, called the organic electronic ion pump, is used to electronically control amyloid-like aggregation kinetics and morphology of peptides, and offers an interesting method for studying amyloids in vitro. Second, various ion-conducting diodes based on bipolar membranes are described. These diodes show high rectification ratio, i.e. conduct ions better for positive than for negative applied voltage. Simple ion diode based circuits, such as an AND gate and a full-wave rectifier, are also reported. The AND gate is intended as an addressable pH pixel to regulate for example amyloid aggregation, while the full-wave rectifier decouples the electrochemical capacity of an electrode from the amount of ionic charge it can generate. Third, an ion transistor, also based on bipolar membranes, is presented. This transistor can amplify and control ionic currents, and is suitable for building complex ionic logic circuits. Together, these results provide a basic toolbox of ionic components that is suitable for building more complex and/or implantable organic bioelectronic devices.v Populärvetenskaplig SammanfattningItalienaren Luigi Galvani experimenterade under 1700-talet med vad han kallade animalisk elektricitet, eller bioelektricitet. Genom att vidröra en död grodas benmuskler med olika metallelektroder kunde Galvani framkalla rörelser i grodans ben. Detta kan anses vara starten för användandet av elektricitet för att studera, mäta eller stimulera levande biologiska system och processer. Det senaste århu...

Conducting Polymer Electrodes for Thermogalvanic Cells

“…Therefore, these electrons are no longer assigned to a single atomic orbital but to a molecular orbital (MO) (24). MO's are linear combinations of the atomic orbitals (25). When these atomic orbitals, wave functions constructively interfere, there is a higher probability of finding the electrons in between the atomic nuclei.…”

“…These two different structures of trans-polyacetylene have the identical energy (24), i.e., the equal probability of occurring and can thus coexist in two domains on the same chain. This creates a transition region between the two domains (with different bond length alternation), which is associated with an unpair electron, and it is known as a soliton (25,34). In a neutral conjugated polymer, the lowest electronic transition has the excitation energy corresponding to its band gap, typically in the UV and visible light region (UV-Vis), and it is highly involved in the definition of the color of the polymer (16).…”

“…Hybridized Orbitals of Carbon. The orbitals with dotted outline/blue-yellow are nonhybridized p orbitals [adapted from(25)]. …”

“…The molecule (a) ethane consists only of 3 single bonds with two sp 3 carbons, (b) ethylene consist with a double bond with two sp 2 carbons and (c) ethyne has a triple bond with two sp carbons [adapted from(25)]. …”

“…The energy diagram of the formation of π orbitals of polyacetylene of different length [adapted from(24,25)]. …”