Realization of advanced bio-interactive electronic devices requires mechanically compliant sensors with the ability to detect extremely large strain. Here, we design a new multifunctional carbon nanotube (CNT) based capacitive strain sensors which can detect strains up to 300% with excellent durability even after thousands of cycles. The CNT-based strain gauge devices exhibit deterministic and linear capacitive response throughout the whole strain range with a gauge factor very close to the predicted value (strictly 1), representing the highest sensitivity value. The strain tests reveal the presented strain gauge with excellent dynamic sensing ability without overshoot or relaxation, and ultrafast response at sub-second scale. Coupling these superior sensing capabilities to the high transparency, physical robustness and flexibility, we believe the designed stretchable multifunctional CNT-based strain gauge may have various potential applications in human friendly and wearable smart electronics, subsequently demonstrated by our prototypical data glove and respiration monitor.R ecent developments in flexible and stretchable electronics, either through structural consideration or by exploring novel materials 1,2 , have imparted otherwise rigid and brittle electronic devices mechanical compliance and bio-compatibility, paving the way for energy-efficient, lightweight, portable, wearable and even implantable electronics 3 . Examples include stretchable and large area display that can undergo complex deformations 4 , bio-inspired material and structural designs that enable bionic functions 5 , and printable sensory system capable of detecting planar strains, normal pressure, temperature, light, moisture and chemical/biological species 6 . Multifunctional sensors, in particular, with sensing abilities akin to or beyond those of human skin 6-12 , are essential for applications such as interactive electronics 13 , structural health monitoring 14 , smart clothing 15 , robotic systems with advanced sensing capabilities 16 , human motion detection 8 and so on. Among the various types of sensors, strain gauge is one of the most important smart sensors, which have been widely used in the measurements of strain, acceleration and tension, as well as structural health monitoring. Conventional strain gauges, made of metal foils, register resistance changes under tensile strains. Actually, mechanical compliance and large strain range (?5%), obviously not the case of metal foils, are required to meet the demands of wearable electronics 15 , human motion detection 8 and interactive robots 17 . Although mercury-in-rubber strain gauge has been used in the biological measurements for decades 18 , the maximum strain limit and toxicity of mercury still block their practically wide applications. In addition, the combination of conformability and optical transparency will facilitate intelligent electronics and self-powered robot where strain sensors are integrated with optoelectronic devices and direct observation through the devices is ne...

It is a great challenge to substantially improve the practical performance of flexible thermoelectric modules due to the absence of air-stable n-type thermoelectric materials with high-power factor. Here an excellent flexible n-type thermoelectric film is developed, which can be conveniently and rapidly prepared based on the as-grown carbon nanotube continuous networks with high conductivity. The optimum n-type film exhibits ultrahigh power factor of ∼1,500 μW m−1 K−2 and outstanding stability in air without encapsulation. Inspired by the findings, we design and successfully fabricate the compact-configuration flexible TE modules, which own great advantages compared with the conventional π-type configuration modules and well integrate the superior thermoelectric properties of p-type and n-type carbon nanotube films resulting in a markedly high performance. Moreover, the research results are highly scalable and also open opportunities for the large-scale production of flexible thermoelectric modules.