An Adhesive Surface Enables High-Performance Mechanical Energy Harvesting with Unique Frequency-Insensitive and Pressure-Enhanced Output Characteristics.

Viscoelastic polymer adhesives (VPAs) are common materials broadly used in adhesive tapes for bonding objects tightly in daily life. This work presents a conceptually new strategy of using contact electrification (rather than strong adhesion) of VPAs to directly convert mechanical energy to electric energy, generally showing 202-419% of the electric energy generated by conventional mechanical energy harvesters under the same triggering conditions. More notably, the VPA-based generators (VPAGs) possess unique frequency-insensitive and pressure-enhanced output characteristics. The output power of a VPAG not only does not show regular degradation of performance with the decrease of triggering frequency, but also can be further enhanced by simple introduction of a second VPA layer with a smaller area to increase the applied pressure without the requirement of rising applied force. The average output power density of a VPAG with a second layer of 0.5 cm × 0.5 cm can reach 216.7 µW cm-2 , which is ≈150% larger than that of a VPAG without a second VPA layer. This research is of significance to harvesting the random, irregular, and low-frequency (bio-)mechanical energy that widely exists but is wasted in the environment for both stable electric energy generation and electronic device operation.