Ionic Circuits for Transduction of Electronic Signals into Biological Stimuli
Abstract: Modern electronics has revolutionized the way information is processed and stored in our society. In health care and in biology it is of great interest to utilize technology to regulate physiology and to control the signaling pathways. Therefore, the coupling of electronic signals to biological functions is of great importance to many fields within the life sciences. In addition to the conventional inorganic electronics, a new branch of electronics based on organic materials has emerged during the last three decades. Some of these organic materials are very attractive for interacting with living systems since they are soft, flexible and have benevolent chemical properties.This thesis is focused on the development of ionic circuits for transduction of electronic signals into biological stimuli. By developing such an intermediate system technology between traditional electronics and biology, signals with chemical specificity may be controlled and addressed electronically. First, a technology is described that enables direct conversion of electronic signals into ionic ones by the use biocompatible conductive polymer electrodes. The ionic bio-signals are transported in lateral channel configurations on plastic chips and precise spatiotemporal delivery of neurotransmitter, to regulate signaling in cultured neuronal cells, is demonstrated. Then, in order to achieve more advanced ionic circuit functionality, ion bipolar junction transistors were developed. These ion transistors comprise three terminals, in which a small ion current through one terminal modulates a larger ion current between the other two terminals. The devices are functional at physiological salt concentrations and are utilized to modulate neurotransmitter delivery to control Ca2+ signaling in neuronal cells. Finally, by integrating two types of transistors into the same chip, complementary NOT and NAND ion logic gates were realized for the first time. Together, the findings presented in this thesis lay the groundwork for more complex ionic circuits, such as matrix addressable delivery circuits, in which dispensing of chemical and biological signals can be directed at high spatiotemporal resolution.
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