Safe DC Neural Stimulation via Ionic Conduction and Valve Sequencing
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Solution Overview
Problem
Neural prostheses are limited in their ability to both excite and inhibit neurons efficiently, as direct current (DC) stimulation is biologically unsafe due to electrochemical reactions at the metal electrode-tissue interface, and existing solutions using alternating current (AC) pulses are insufficient for treating disorders requiring both excitation and inhibition.
Innovation Solution
A device and method that directs DC flow into target tissue by switching mechanical valves in phase with AC square waves applied to electrodes immersed in an ionic solution, maintaining DC ionic current through the tissue while avoiding electrochemical reactions, using a bipolar configuration to prevent pH changes and employing ionic diodes for controlled ion flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If direct current (DC) stimulation is applied to metal electrode in contact with neural tissue, then neural activity can be excited or inhibited, but electrochemical reactions occur at the electrode-tissue interface causing safety hazards
Solution Approach 1:
The patent introduces an ionic solution as an intermediary medium between the metal electrode and the neural tissue. The electrode is immersed in the ionic solution rather than directly contacting the tissue, allowing DC current to be delivered to the tissue through the solution without direct metal-tissue contact. This intermediary layer prevents electrochemical reactions at the tissue interface while still enabling effective neural stimulation through the ionic conductive path.
Solution Approach 2:
The patent replaces the traditional direct electrical contact mechanism with a fluid-mediated ionic conduction system. Instead of relying on direct electron transfer through metal-tissue contact, the system uses ion flow through the ionic solution to deliver current to the neural tissue, substituting a chemical/ionic mechanism for the direct electrical contact approach.
2Reliability
If alternating current (AC) pulses are used to stimulate neurons, then safety issues are avoided, but the ability to both excite and inhibit neurons is insufficient
Solution Approach 1:
The patent changes the key parameter of current type from alternating current (AC) to direct current (DC). DC current provides a constant polarity that enables both excitatory and inhibitory effects on neurons, whereas AC pulses only provide excitatory effects. By maintaining DC current through the ionic solution medium, the system achieves both safety and the enhanced capability to modulate neural activity in both directions.
3Duration of action of stationary object
If mechanical valves are used to direct DC flow into target tissue, then uninterrupted current delivery is achieved, but current interruptions occur during valve transitions
Solution Approach 1:
The patent employs multiple mechanical valves that are sequentially activated to maintain continuous DC current flow through the tissue. As one valve closes, another opens, ensuring that the ionic current path remains uninterrupted. This sequential valve operation prevents gaps in current delivery that would otherwise occur during valve state transitions, maintaining both continuity and stability of the therapeutic current.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables uninterrupted and safe delivery of direct current to neural tissue, reducing undesirable neural activity and enhancing the capabilities of neural prostheses to treat various neurological disorders by achieving graded control of neural activity and simultaneous excitation and inhibition.
Implementation Method 1
A tube is filled with conductive material and configured to direct the direct current flow of ions into target tissue
Implementation Method 2
a first set of valves and a second set of valves configured to be opened and closed and further configured to switch in phase with alternating current applied to the first electrode and the second electrode
Data Source
AI summary
An embodiment in accordance with the present invention provides a device and method to deliver direct ionic current safely to target neural tissue, while also eliminating interruptions in the output of the device that can result from the non-ideal operation of the valves used to control the current flow in the device. The device includes two valve-operated systems that work in tandem. The first and second current producing systems are configured to be used together in order to eliminate the periodic interruptions in current flow. In use, one system drives current through the target tissue, while the other system closes all of the valves first and then opens its valves in sequence. This intermediate step of closing all of the valves prevents unintended current shunts through either system. The device also includes two conductors to direct the flow of direct current into the target tissue.