. Author manuscript; available in PMC: 2024 May 8.

Published in final edited form as: ACS Biomater Sci Eng. 2021 Nov 16;9(5):2048–2069. doi: 10.1021/acsbiomaterials.1c00741

Table 2.

Summary of the Biosignal Readouts for Wearable Devices

output	principle	advantages	typical applications
Geometrical	Changing conformational/cross-linking properties	Easy to fabricate	Strain sensor¹³⁴
Geometrical	Changing conformational/cross-linking properties	Cost-efficient	Soft actuators, robots^121,135
Optical	Photonic structures	Cost-efficient	Bionic electronic skin^136,137
	Structure color	Naked-eye readout	Colorimetric/florescent sensors^138,139
	Florescent/color additives	Instrument-free
Electrical	Intrinsically conductive hydrogels or embedded conductive micro/nanomaterials	Real-time measurement	Hydrogel electronics^140,141
		High sensitivity	Wearable sensors^123,142
		Integrated	Hydrogel skin^143,144
Biological	Biological events in hydrogel	Biocompatible	Microneedles^124,145,146
Biological	Biological events in hydrogel	Air and nutrient permeable Wearable sensors¹⁴⁷	Air and nutrient permeable Wearable sensors¹⁴⁷