Neurotransmitters control signal transmission in the nervous system. The signals of neuron cells can be excited or inhibited based on the types of neurotransmitters that are released from pre-synaptic neurons. The balance of the excitatory and inhibitory synaptic responses has important implications for the versatility, plasticity, and parallel computing characteristics of the nervous system. Emulating the excitatory-inhibitory balancing characteristics is one way to establish the versatility and plasticity characteristics of the brain. In this study, the authors develop artificial synapses to emulate the excitatory and inhibitory functions of biological synapses using electrochemical reactions between the channel and neurotransmitter solutions. The devices show excitatory and inhibitory characteristics depending on types of neurotransmitter solutions. The interaction between these two types of synaptic responses is employed for emulating the excitatory-inhibitory balance characteristics. The devices emulate the multifunctional characteristics of biological synapses, resulting in their potential for use in bio-realistic neuromorphic devices.
Liquid-based devices have emerged as bioinspired neuromorphic applications owing to their high ion-diffusion coefficients, diverse structures, and controllable ion-exchange reactions. By engineering and modifying liquid materials, multifunctional liquid-based computing devices have been developed for next-generation memory and neuromorphic devices. The unique properties of liquids make them feasible for memory functions and various synaptic applications, such as emulating synaptic plasticity, homeostasis, and action potentials. Utilizing liquids in computing devices provides a promising and versatile platform for high-performance memory devices and enables the emulation of bioinspired computing functions. In this Spotlight, we highlight recent advances in liquid-based memory devices and focus on synaptic applications. We then discuss possible array structures and scaling-down technologies for liquid-based devices. Finally, the challenges and future prospects of liquid-based devices are discussed.
Neurons are vital components of the brain. When stimulated by neurotransmitters at the dendrites, neurons deliver signals as changes in the membrane potential by ion movement. The signal transmission of a nervous system exhibits a high energy efficiency. These characteristics of neurons are being exploited to develop efficient neuromorphic computing systems. In this study, we develop chemical synapses for neuromorphic devices and emulate the signaling processes in a nervous system using a polymer membrane, in which the ionic permeability can be controlled. The polymer membrane comprises poly(diallyl-dimethylammonium chloride) and poly(3-sulfopropyl acrylate potassium salt), which have positive and negative charges, respectively. The ionic permeability of the polymer membrane is controlled by the injection of a neurotransmitter solution. This device emulates the signal transmission behavior of biological neurons depending on the concentration of the injected neurotransmitter solution. The proposed artificial neuronal signaling device can facilitate the development of bio-realistic neuromorphic devices.
Warpage is a critical concern in printed circuit boards (PCBs) because it can result in various issues, such as solder joint failure, electrical shorts, and compromised mechanical integrity. This study investigates the warpage behavior of PCBs by considering the structure of a Cu trace using finite element analysis simulations. Four types of Cu trace structures were investigated depending on the placement of Cu. The warpage behavior was analyzed by systematically varying these parameters and subjecting the PCB to simulated thermal and mechanical stresses. The effects of different material properties, such as the coefficient of thermal expansion of the PCB substrate and copper layers, were considered. The results provide valuable insights into the relationship between the trace structure and PCB warpage, which can help engineers and designers make informed decisions regarding PCB layout and manufacturing processes. Moreover, optimizing the trace structures facilitates the minimization of the warpage and reliability enhancement while ensuring the proper functioning of PCBs in various electronic applications.
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