A multifunctional wearable sensor based on a graphene/inverse opal cellulose film for simultaneous, in situ monitoring of human motion and sweat.

A multifunctional, wearable sensor based on a reduced oxide graphene (rGO) film onto a porous inverse opal acetylcellulose (IOAC) film has been developed and can perform simultaneous, in situ monitoring of various human motions and ion concentrations in sweat. The rGO film is used as a strain-sensing layer for monitoring human motion via its resistance change, whereas the porous IOAC film is used as a flexible microstructured substrate not only for high sensitive motion sensing, but also for collection and analysis of ion concentrations in sweat by its simple colorimetric changes or reflection-peak shifts. Studies on humans demonstrated that the devices have excellent capability for monitoring various human motions, such as finger bending motion, wrist bending motion, head rotation motion and various small-scale motions of the throat. Simultaneous, in situ analysis of the ion concentration in sweat during these motions shows that the IOAC substrate can detect a wide range of NaCl concentrations in sweat from normal 30 to 680 mM under the conditions of severe dehydration. This investigation provides new horizons toward the design and fabrication of multifunctional, wearable health monitoring devices and the proposed wearable sensor shows promising applications in healthcare and preventive medicine.

Colorimetric photonic hydrogel aptasensor for the screening of heavy metal ions.

We have developed a robust method for the visual detection of heavy metal ions (such as Hg(2+) and Pb(2+)) by using aptamer-functionalized colloidal photonic crystal hydrogel (CPCH) films. The CPCHs were derived from a colloidal crystal array of monodisperse silica nanoparticles, which were polymerized within the polyacrylamide hydrogel. The heavy metal ion-responsive aptamers were then cross-linked in the hydrogel network. During detection, the specific binding of heavy metal ions and cross-linked single-stranded aptamers in the hydrogel network caused the hydrogel to shrink, which was detected as a corresponding blue shift in the Bragg diffraction peak position of the CPCHs. The shift value could be used to estimate, quantitatively, the amount of the target ion. It was demonstrated that our CPCH aptasensor could screen a wide concentration range of heavy metal ions with high selectivity and reversibility. In addition, these aptasensors could be rehydrated from dried gels for storage and aptamer protection. It is anticipated that our technology may also be used in the screening of a broad range of metal ions in food, drugs and the environment.