Construction of sandwich-like porous structure of graphene-coated foam composites for ultrasensitive and flexible pressure sensors.

Ultrasensitive and flexible pressure sensors that can perceive and respond to environmental stimuli have attracted considerable attention due to their potential applications in wearable electronics and electronic skin devices. Here, we report a simple and low-cost strategy to fabricate high-performance pressure sensors via constructing a unique conductive/insulating/conductive sandwich-like porous structure (SPS). Interpenetration of the conductive graphene network throughout the porous insulating interlayer produces a highly efficient transition from the non-conductive to the conductive state. Consequently, the SPS sensors exhibit an extreme resistance-switching behavior (resistance change of >105 at 30 kPa), high sensitivity (∼0.67 kPa-1, <1.5 kPa), fast response/recovery time (∼10 and ∼16 ms) and outstanding mechanical stability. Such SPS pressure sensors are applicable for detecting various mechanical deformation modes (press, bend and torsion) and different stress/strain levels (from gait feature, finger/wrist/elbow movement to breathing monitoring and real-time pulse wave), providing a new concept of device design for wearable electronic applications.

Synergistic strengthening of polyelectrolyte complex membranes by functionalized carbon nanotubes and metal ions.

Hydrophilic polymers have garnered much attention due to their critical roles in various applications such as molecular separation membranes, bio-interfaces, and surface engineering. However, a long-standing problem is that their mechanical properties usually deteriorate at high relative humidity (RH). Through the simultaneous incorporation of functionalized carbon nanotubes and copper ions (Cu(2+)), this study introduces a facile method to fabricate high strength polyelectrolyte complex nanohybrid membranes resistant to high RH (90%). For example, the tensile strength of the nanohybrid membranes is 55 MPa at 90% RH (80% of the original value at 30% RH). These results are explained by copper ions depressing the swelling degree of the membrane, and functionalized carbon nanotubes promoting stress transfer between the polymer matrix and them. The nanohybrid membranes are efficient in separating water/alcohol mixtures containing relatively high water content (up to 30 wt%), whereas common hydrophilic polymer membranes usually suffer from excessive swelling under this condition.

Bio-filler from waste shellfish shell: preparation, characterization, and its effect on the mechanical properties on polypropylene composites.

Waste shellfish shell stacking with a significant odor and toxicity which are hazardous to human constitutes a serious environmental hazard. For utilization of waste shellfish shell resource, granule of shellfish shell (SS) was prepared from waste shellfish shell by removing cuticle, crushing, grinding and shearing emulsification and was introduced as a filler to reinforce polypropylene (PP). The mechanical behavior of PP/SS composite shows a higher yield strain, yield strength, tensile strength and elongation at break than traditional commercial calcium carbonate (CC) filled PP. Yield strength of PP/SS composite with 2% SS is improved by 11.1% due to the formation of ß-crystalline PP phase. Using waste SS for producing bio-filler for filling PP is an effective and prospective measure to deal with waste SS, which is valuable for industrial production and practical application as fillers for reinforcing polymers.