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Page 18 of 38 Wei et al. Soft Sci 2023;3:17 https://dx.doi.org/10.20517/ss.2023.09

types of complex human motions that are impossible to be distinguished by a single strain sensor or EMG
sensor.

Another example of a physical/physiological hybrid sensing system is a skin-tight electronic shirt
integrating a strain sensor, an ECG sensor, and an EMG sensor on it. Direct stencil printing was used to
apply a silver-fluoroelastomer-mixed composite ink onto an electrospun PVDF nanofiber sheet in order to
[172]
form a nanofiber-reinforced elastic conductor . Then the as-prepared elastic conductor was transferred
onto a shirt using a press process to fabricate a strain sensor, an ECG sensor, and an EMG sensor on
appropriate sites of the shirt (as shown in Figure 8D). After a wireless transmission module was integrated,
the e-shirt could be used as a multimodal electronic fabric sensor system for long-term continuous
monitoring of physiological activities.

To achieve a higher-level integration of sensing textile platforms, integrating multiple signals sensors on one
garment may reflect a development trend of wearable fabric sensors in the future. For example, Kapoor et
al. put forward a design concept of integrating multimodal fabric sensing units on one long-sleeved shirt (as
shown in Figure 8E) . They arranged resistance-type fabric sensors for pulse monitoring or fabric
[173]
electrodes for measuring bioelectrical signals on the chest. They also placed humidity sensors based on
impedance changes under the armpit to monitor sweat and weaved tactile input sensors based on
capacitance changes on the inner arm. At the same time, the author proposed that all fabric sensors could be
realized by fibers based on a continuous extrusion printing process and could be assembled into sensor
arrays by commercial roll-to-roll weaving process for mass production.

The physical/chemical-type multimodal sensing textile is another aspect of hybrid signal sensing that is
worth exploring. Many previous studies have already involved this idea. A well-known study is a
multi-channel fully integrated sweat sensor reported by Gao et al., which can selectively detect sweat
electrolytes (Na and K ) and metabolites (glucose and lactic acid) with a temperature sensor embedded in
+
+
[174]
to correct the response of the bio-enzyme sensing unit . In addition, a multi-sensor device, integrating
strain, ultraviolet light, and NO gas sensing, was manufactured to conveniently monitor signals from the
2
human body and environment . However, previous efforts are mainly focused on non-textile platforms.
[175]
For textile-based sensing, Tang et al. proposed a bimodal sensor that detects pressure and gas concentration
signals, which could be used to detect and distinguish tactile and olfactory stimuli on a single sensing unit
[176]
(as shown in Figure 8F) . The polyaniline (PANI) fabric was sensitive to the concentration of ammonia in
the air, while the contact area between the fabric and the interdigital electrode was related to the pressure
applied to the sensor. This allowed for the realization of the pressure-dependent resistance change. The
resistance of the dual-mode sensing fabric increased with the increase of ammonia concentration in the
environment and decreased with the increase of pressure applied. This allowed for the detection and
distinction of both tactile and olfactory stimuli.

To the best of our knowledge, although hybrid signal sensing textiles have been widely studied, multimodal
textiles that combine physical and chemical signals, as well as physical, physiological, and chemical signal
multi-sensing, are rarely reported; therefore, further research is warranted.

APPLICATION IN HUMAN-MACHINE INTERFACE
The development of smart textile manufacturing processes has facilitated the rise of multimodal electronic
textiles, providing a viable strategy for multimodal sensing of physical, physiological, chemical, and hybrid
signals. Designed through fiber fabrication and textile forming techniques, multimodal electronic textiles