by Dominik Dietze
Product Manager (Brain Products)
We at Brain Products continuously strive for improvement and for solutions that make the life of our customers easier, this is best done by continuously extending our offering with the latest EEG recording technology. That is why we are introducing our new Hydrogel Headset with the new solid gel electrode technology. The new headset comes with 6 EEG recording positions on the forehead orienting on the 10/20 system (Fpz, AF7, AF8, Fz, F3, F4) it also comes with 2 bipolar inputs that can be used for e.g. ECG recording or any Sensor with bipolar output e.g. respiratory flow or respiratory movement.
Let’s start with an introduction of the Headset itself. The idea is to have a one size fits all rigid frame construction. This can be achieved with a simple mechanism that allows you to adjust the headset for different head circumferences. This is a mechanism that anyone who has worn helmets for cycling or skiing will be familiar with. The rotary knob on the back of the frame does exactly this job. Rotating “clockwise” reduces the diameter, rotating “counterclockwise” increases the diameter. This is the first degree of freedom that we should provide in a ‘one size fits all’ concept. The next is the different head geometries that need to be compensated for with an additional adjustment option. For this we have electrodes that can be screwed in and out of their holders to give an additional length adjustment option perpendicular to the frame. “Clockwise” rotation moves the electrode in and brings the electrode tip closer to the head (i.e. increases the pressure of the tip on the skin), “counterclockwise” rotation moves the electrode out and moves the electrode tip further away from the head (i.e. decreases the pressure of the tip on the skin).
But this is not the only thing the electrodes are doing, they are also holding the hydrogel tip. To insert the hydrogel tip into the electrode, the holding mechanism must be opened by “counterclockwise” rotation. Once opened, the hydrogel tip can be loaded into the holder and the holder must be fixed back to the electrode by clockwise rotation until a click indicates the end position.
To save subjects time it is recommended to screw in the electrodes into the frame before loading them with the electrode tips.
Now let’s talk about the electrode tips. These are made of hydrophilic polymer. The material has a solid appearance comparable to a jelly baby. If exposed to air it evaporates water and shrinks. It shrinks to approximately 1/5 of the fully watered size. When again exposed to water it takes in as much water required until it reaches the original shape and geometry.
Due to the high intake capacity of saline solution into the polymer material and the slow release of it over time it is the ideal electrolyte material.
The solid non-sticky material and the rather small amount of saltwater that is released during the contact means the surface between skin and electrode can be considered as residue free. The elasticity of the material even allows you to use a certain amount of pressure to improve the contact while keeping the subjects comfort at the same level as with our active electrodes.
The tips are considered as single subject use, so from the perspective of in between subject cleaning and disinfecting, there is no time wasted by removing gel residues from electrodes. Just open the holders, exchange the tips and you are good to go for the next recording. The whole preparation process in between subjects takes less than 3 minutes whilst still maintaining high hygiene standards.
The Hydrogel Headset can be considered as an ideal solution for researchers that are particularly interested in mobile recording of frontal EEG activity, combined with other parameters such as ECG and for example a respiration sensor.
The Hydrogel Headset comes with unmatched speed of application, lowest inter subject preparation time combined with high hygiene standards and a one size fits all concept.
Interested? Please contact us (firstname.lastname@example.org) or your local Brain Products distributor for a system demonstration an/or a quotation.