Page 173 - Read Online

Page 12 of 15 Tu et al. Soft Sci 2023;3:25 https://dx.doi.org/10.20517/ss.2023.15

interference (crosstalk). Large-area fabrication and integration on irregular three-dimensional surfaces also
bring huge difficulties in sensor resolution, layer-to-layer registration, and large-area uniformity. In
addition, a high level of integration inevitably results in a short distance between sensors and processing
units. The signal-to-noise ratio is thus affected by the smaller spaces for sensing external stimuli. Novel
electrode materials, device architecture, and large-area fabrication techniques are required to solve these
problems.

(iii) Wireless communication. In e-skin systems, wireless communication deserves more research attention.
This technique can get rid of additional wiring in other to alleviate the spatial limits and disturbance. So far,
most wireless e-skin systems have been based on conventional wireless techniques, such as Bluetooth and
near-field communication. The need for flexibility and stretchability gives rise to electromagnetic coupling,
where signals are transmitted between internal and external coils. However, signal interference caused by
other working electronics, the permittivity of the surrounding environment, and motions restricts the wide
application of electromagnetic coupling in e-skin systems. These issues should be fully addressed, and novel
wireless communication techniques are in need to construct wireless e-skin systems with the growing
demand for Internet-of-Things.

(iv) Optimum of bottom-up multimodal algorithms. More effort remains to be put into e-skins based on
bottom-up multimodal perceptual fusion. Near-/in-sensor computing requires more advanced
neuromorphic computing devices. These devices are suitable for neural network algorithms to realize
device-level multimodal perception. Thus, problems, such as power efficiency and fault tolerance, can be
suppressed when the size of the data is highly increased. Apart from algorithms, including SVMs, clustering
methods, CNNs, and ANNs, the software-level bottom-up multimodal perception requires more advanced
algorithms models and architectures to overcome the challenges of fusing the datasets from heterogeneous
modalities and dealing with missing data or different levels of noise.

(v) Development of top-down multimodal algorithms. Top-down selective attention is necessary to
function for more efficient multisensory integration processes in this situation. However, the area of top-
down attention-based multimodal perception fusion of e-skins is still blank but highly worthy of being
discovered. As growing attention-based fusion research on other areas, such as speech recognition and
video captioning, keeps arousing, there will be a better chance for e-skin systems to accomplish brain-like
perception and cognition.

DECLARATIONS
Acknowledgments
The authors gratefully acknowledge the support from the National Natural Science Foundation of China
(Grant Nos. U20A6001 and 11921002).

Authors’ contributions
Conceptualization: Tu J, Wang M
Methodology: Tu J, Wang M
Writing - Original Draft: Tu J, Wang M
Writing - Review & Editing: Li W, Su J, Li Y, Lv Z, Li H, Feng X, Chen X
Supervision: Feng X, Chen X

Availability of data and materials
Not applicable.