Highly Efficient Cellular Acoustic Absorber of Graphene Ultrathin Drums.

Atomically thin 2D graphene sheets exhibit unparalleled in-plane stiffness and large out-of-plane elasticity, thereby providing strong mechanical resonance for nanomechanical devices. The exceptional resonance behavior of ultrathin graphene, which promises the fabrication of superior acoustic absorption materials, however, remains unfulfilled for the lack of applicable form and assembly methods. Here, a highly efficient acoustic absorber is presented, wherein cellular networks of ultrathin graphene membranes are constructed into polymer foams. The ultrathin graphene drums exhibit strong resonances and efficiently dissipate sound waves in a broad frequency range. A record specific noise reduction coefficient (51.3 at 30 mm) is achieved in the graphene-based acoustic absorber, fully realizing the superior resonance properties of graphene sheets. The scalable method facilely transforms commercial polymer foams to superior acoustic absorbers with a ≈320% enhancement in average absorption coefficient across wide frequencies from 200 to 6000 Hz. The graphene acoustic absorber offers a convenient method to exploit the extraordinary resonance properties of 2D sheets, opening extensive new applications in noise protection, building design, instruments and acoustic devices.

A Flexible Pressure Sensor with Ink Printed Porous Graphene for Continuous Cardiovascular Status Monitoring.

Flexible electronics with continuous monitoring ability a extensively preferred in various medical applications. In this work, a flexible pressure sensor based on porous graphene (PG) is proposed for continuous cardiovascular status monitoring. The whole sensor is fabricated in situ by ink printing technology, which grants it the potential for large-scale manufacture. Moreover, to enhance its long-term usage ability, a polyethylene terephthalate/polyethylene vinylacetate (PET/EVA)-laminated film is employed to protect the sensor from unexpected shear forces on the skin surface. The sensor exhibits great sensitivity (53.99/MPa), high resolution (less than 0.3 kPa), wide detecting range (0.3 kPa to 1 MPa), desirable robustness, and excellent repeatability (1000 cycles). With the assistance of the proposed pressure sensor, vital cardiovascular conditions can be accurately monitored, including heart rate, respiration rate, pulse wave velocity, and blood pressure. Compared to other sensors based on self-supporting 2D materials, this sensor can endure more complex environments and has enormous application potential for the medical community.