Question

Adjacent to the channel walls, the charge-neutrality of the liquid is violated due to the presence of the electrical double layer: a thin layer of counterions attracted by the charged surface. The transport of counterions along with the pressure-driven fluid flow gives rise to a net charge transport: the streaming current. But when I asked the chat.openai, it said No, a porous medium does not necessarily have to be charged to establish streaming potential. Streaming potential can arise in a porous medium when a fluid flows through it, and there is a pressure gradient across the medium. This can create a charge separation in the pore fluid due to the movement of ions, resulting in an electric potential difference across the medium. The zeta potential, which is the potential difference between the surface of the porous medium and the bulk fluid, can influence the magnitude and direction of the streaming potential. However, even in the absence of a zeta potential, a pressure-driven flow can induce a streaming potential in the pore fluid. So, now I'm a bit confused.

Answer 1

A streaming current is generated when ions in a fluid flow through a channel or porous medium, leading to a net charge transport. In biological systems, this is observed in the charge separation across a neuron's semi-permeable membrane, resulting in a membrane potential. A porous medium does not need to be charged to establish a streaming potential; it can occur due to a pressure gradient leading to ion movement.

Step-by-step explanation:

Understanding Streaming Current and Electrical Double Layers

The concept of a streaming current arises when a fluid, containing charged molecules or ions, flows through a channel or porous medium. The ions are attracted and reoriented near the charged surface of the medium creating what is known as the electrical double layer. When the fluid moves, these layers of ions also move, resulting in the net transport of charge, which is referred to as the streaming current. This phenomenon is crucial in understanding electrical properties in biological systems, like neurons, and also in engineered systems such as sensors and energy storage devices.

The electrical gradient across a cell membrane, as described in the information provided about neurons, is an analogous concept where ions like Na+, K+, and Cl- contribute to a potential difference across the membrane. This is due to the membrane being semi-permeable, allowing certain ions to pass while restricting others, resulting in charge separation and thus a membrane potential.

When considering streaming currents in a porous medium, the charge of the medium is one factor that can influence the potential, but it is not a necessity for the generation of the streaming potential. The movement of ions due to a pressure gradient, even in the absence of a charged medium, can lead to charge separation and hence a potential difference. This concept is analogous to the way ions create an electrical gradient across a neuronal cell membrane, even though the fluids on either side are electrically neutral.