Introduction of actiCAP Xpress Twist – Brain Products’ next generation dry electrode system

When we first introduced the 16 channels actiCAP Xpress back in the spring of 2014 the product was received very positively from the research community. Its innovative design resolved many of the issues that existing products had and therefore, naturally, everybody was also wishing to be able to use the same system with 32 channels and other Brain Products amplifiers.

Despite the great feedback received, we knew that extending the actiCAP Xpress to a higher channel count would not have represented an optimal solution. Adjusting the lengths of the electrodes individually by exchanging QuickBits of different lengths in order to optimize the contact with the scalp, would have been very time-consuming and cumbersome with more than 16 channels.

In order to overcome this problem and maintain all the good features of the actiCAP Xpress system we kept the concept of using gold-plated, mushroom-shaped electrode bits that can be easily exchanged. But, we applied the “Twist” mechanism that now allows fast adjustment of the individual electrode length by simply screwing in and out the electrode in the holder.

actiCAP Xpress Twist: 32 channel active dry electrode system

The combination of well-known and tested actiCAP Xpress components with the new “Twist” mechanism translates into a superior, high channel count, dry electrode system – the actiCAP Xpress Twist – offering the following advantages:

Thanks to the “Twist” mechanism, adjusting the optimal height and pressure for the individual electrode position is as easy as … one, two and three.

As you know, with dry electrodes the function of the gel is replaced by a certain amount of pressure that has to guarantee a steady contact between the electrode and the scalp. With the twist mechanism and the particular electrode shape, it is very easy and fast to find the best possible contact. The accessibility of the electrode tips through the openings in the cap and the fast length adjustment of the electrodes, thanks to the Twist mechanism, results in a very short cap preparation time. Taking into account that the time until your participant reaches its individual tolerance level starts with the preparation, then it is obvious that a reduced preparation time leaves you more time for your experiments. With the “Twist” system, preparation times of less than 3 minutes for a 32 channel set up can be achieved.

Wherever a fast setup with no gel residuals of the EEG cap is required and a limited EEG recording bandwidth can be accepted (for our dry systems we recommend 1 Hz – 40 Hz), then dry electrodes are the optimal solution. Within the typical frequency range of dry electrode systems, our actiCAP Xpress Twist guarantees an outstanding data quality. To outline it we made a comparison measurement between our conventional gel-based active electrodes and the new Twist system.

Measurements were performed with the LiveAmp amplifier. A visual stimulation with a flashing checkerboard was used. Triggers were generated with a photo sensor and our StimTrak. In both cases (active electrodes vs. twist electrodes), 105 segments were recorded and averaged.

Results of a comparison measurement between active gel electrodes (red) and the actiCAP Xpress Twist dry electrode system (blue).

Participant comfort and dry electrodes are 2 things that usually exclude each other, especially for long recording times. As already mentioned, in dry electrode systems, the gel is replaced by a certain amount of pressure. The level of comfort or discomfort is participant specific and varies throughout the subject population. The design used for the actiCAP Xpress Twist improves the comfort immensely; this translates into longer recording times.

The large ventilation holes in the cap assure proper ventilation, minimize sweat and allow the user to access the electrode tips while the cap is mounted.

The fabric used is of soft, flexible and pleasant neoprene material. Due to the “Twist” mechanism, the pressure applied to the individual positions can be adjusted very quickly and precisely, which limits participant discomfort to an absolute minimum.

When talking about costs for an electrode system, people often forget to factor in the costs that occur through the overall product lifetime. Especially those related to maintenance and repair costs.

As soon as you unpack the product and start using it, it will wear off, this is the unavoidable process of aging.

We as a manufacturer are fully aware of this. Therefore, we always aim to limit these costs for the customer to an absolute minimum level by:

• Using materials of the highest quality – typically resulting in already ultra-long lifespans.
• Designing solutions that allow an easy replacement in case some parts break. All parts and single components of the actiCAP Xpress Twist can be exchanged by the users in the field.

This combination leads to minimum repair and maintenance costs as well as effort, and to maximized system uptime throughout its life.

Each actiCAP Xpress Twist system comes with 2 caps of different size, so that the majority of the adult head shapes are covered. Both caps come with electrode holders at the 32 standard positions. The cap layout is flexibly customizable due to the possibility to add more electrode holders to 78 pre-prepared holes in the cap.

The actiCAP Xpress Twist system can be ordered in two options:

1. To be combined with either the actiCAP ControlBox, when used together with our BrainAmp amplifier family* or for the use with our actiCHamp active electrodes amplifier.
2. To be combined with our new and fully mobile amplifier the LiveAmp.

We wish you great success and hope you are as thrilled as we are with our next generation dry electrode system.