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Page 10 of 33 Arab Hassani. Soft Sci 2023;3:31 https://dx.doi.org/10.20517/ss.2023.23

and stimulation; (E) optical camera image of the CurvIS array and UNE stack connected through the soft FPCB; and (F) university logo
image captured by the CurvIS array [116] . FPCB: Flexible printed circuit board; UNE: ultra-thin neural-interfacing electrodes.

Figure 4. (A) Network of electroreceptors distributed on a ray’s skin for locating nearby prey; (B) schematic illustration of wearable
SAER on a hand; (C) image of wearable SAER attached to the hollow of the hand; (D) a person wearing the SAER to perceive spatial
[117]
information of a dynamic object; and (E) a person wearing the SAER to perceive spatial information of a static object . SAER: Soft
artificial electroreceptor.

layer that blocks electrical noise from the skin of the subject. The top hydrogel layer acts as a shield layer,
and it ensures that the voltage signal of the sensing layer electrodes is responsive to the distance of the
external object, not its direction. To realise reliable adhesion of the 3D-printed hydrogel on the elastomer,
the elastomer surface was first soaked in a solution containing an ultraviolet (UV)-assisted grafting agent.
The hydrogel was then directly printed on the UV-treated elastomer by using a digital light processing
(DLP) 3D printer. By comparing the intensity of the electric fields sensed by each hydrogel receiver in
Figure 4C, the SAER was able to locate the relative position of the object. When wearing the SAER, the
wearer receives spatial information about nearby objects in real time through auditory signals of specific
frequencies generated for each of the receivers. Figure 4D shows the maximum voltage of the blue receiver
corresponding to the auditory signal frequency of 0.5 kHz when the moving ball reaches the hand. By
contrast, the maximum induced voltage peak of the green receiver when the hand passes the static ball
corresponds to the auditory signal frequency of 1.5 kHz, as depicted in Figure 4E. This artificial
electroreceptor allows a human to perceive space, a new sensory modality that does not exist in human