Abstract
Stimuli-responsive colorimetric sensors are promising for various industrial and medical applications due to the capability of simple, fast, and inexpensive visualization of external stimuli. Here we demonstrate a thermoresponsive, smart colorimetric patch based on a thermoresponsive plasmonic microgel embedded in a stretchable hydrogel film. To achieve a fast and efficient thermoresponsive color change, raspberry-shaped plasmonic microgels were fabricated by decorating gold nanoparticles (AuNPs) on poly(N-isopropylacrylamide) (PNIPAM) microgels, which exhibit reversible and strain-insensitive color shifts (between red and grayish violet) in response to a temperature change. The smart colorimetric patch containing a plasmonic microgels exhibits a significant extinction peak shift (176 nm) in a short time (1 s), with a temperature-sensing resolution of 0.2 °C. Moreover, the transition temperature of the plasmonic microgel can be finely tuned by additives and comonomers, so that the exquisite temperature visualization can be conducted over a wide temperature range of 25‒40 °C by assembling plasmonic microgel films with different transition temperatures into an array patch. For proof-of-concept demonstrations, a freestanding smart colorimetric patch was utilized as a spatial temperature scanner and a colorimetric thermometer for a thermoresponsive actuator, which is potentially applicable in smart, wearable sensors and soft robotics.
Highlights
Wearable health-care devices enable continuous health monitoring and offer instructive health-care information and record data for physical activity, electrocardiogram, body temperature, pH of sweat, and ultraviolet (UV) light[1,2]
The thermoresponsive colorimetric sensor can be integrated into a sensor array patch containing plasmonic microgel films with different transition temperatures, which can broaden the range of detectable temperature and visualize skin temperature more precisely when attached to the human skin (Fig. 1c)
In summary, we developed a thermoresponsive, smart colorimetric patch based on raspberry-shaped plasmonic microgels encapsulated in a stretchable PAAm hydrogel film
Summary
Wearable health-care devices enable continuous health monitoring and offer instructive health-care information and record data for physical activity, electrocardiogram, body temperature, pH of sweat, and ultraviolet (UV) light[1,2]. Among these parameters, temperature is one of the main vital signs and is the most essential parameter for the diagnosis of the condition of the human body[2]. There are many candidates for colorimetric sensors, such as photonic crystals[8], thermochromic dye molecules[9], and liquid crystals[10].
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