I have been trying to find out what the (human) electrotactile frequency range is. Since this is a much more experimental method (and more unpleasant) than the traditional vibrotactile method, the research is more limited.
E.g., for vibrotatctile I could find in Sonar and Paik (2016)
The mechanoreceptors responsible for vibrotactile sensation are the rapidly adapting (RA) and Pacinian corpuscle (PC) receptors with perceptible frequencies ranging from 3 to 100 and 100 to 400 Hz, respectively (Choi and Kuchenbecker, 2013).
Actually that seems to contain a typo or misquote of the paper they cite, which puts the PC at 10-500 Hz:
Anyhow, for electrotactile I could only find what some researchers have used in some of their devices, e.g. Okpara et al., 2007:
Based on our prior unpublished work, the four levels of frequency were set at 100, 35, 15 and 10 Hz.
That suggests a lower range perhaps of only 10-100 Hz. But is that the full range range that can be felt using electrotactile stimulation?
It's been suggested to me that it may be exactly the same as for vibrotactile, but a set of slides comparing various methods says about electrotactile:
Stimulate receptors and nerve endings with electric charge passing through the skin
Since there's some suggestion it may bypass receptor (in part), perhaps the results can be different.
What is the frequency range of electrotactile stimulation?