Introduction 258

Materials design for soft and stretchable electronics 259

Liquid metal 259

Patterning 260

Stretchability and self-healing ability 260

Conductive nanomaterials 262

Stretchable electrode 262

Stretchable conductive composites 263

Conductive polymer 265

Structural design for soft and stretchable electronics 266

Buckled topologies 267

Planar IslanddBridge topologies 270

Soft and stretchable sensors 275

Physical sensors 275

Photodetectors 275

Temperature sensor 276

Humidity sensor 277

Mechanical sensor 278

Chemical sensors 280

pH sensor 280

Gas sensor 281

Conclusions and outlook 281 References 282

In recent years, soft and stretchable electronics are emerging as part of a new generation of electronic devices. Owing to their unprecedented material propertiesdsoftness, flexibility, and stretchabilitydcompared to conventional electronics, they enable innovative applications such as flexible lighting, skin electronics, soft robotics, and flexible energy storage. Here, we review the strategies that made these inventions possible. The first approach is to synthesize stretchable materials that are either intrinsically stretchable or stretchable at a macroscale. The second approach is to use materials that lack the inherent stretchability or flexibility required, but instead to induce the necessary properties through carefully structuring. Afterward, some of the representative soft and stretchable sensors made possible using these strategies are explored. Finally, this review concludes with the limitation of the existing soft and stretchable electronics and some suggestions for possible future development.