Dual-Responsive Self-Propulsion Smart Device Steadily Driven by CO2 and H2O2

Unexpected monolayer-to-bilayer transition of arylazopyrazole surfactants facilitates superior photo-control of fluid interfaces and colloids

Interfaces that can change their chemistry on demand have huge potential for applications and are prerequisites for responsive or adaptive materials. We report on the performance of a newly designed n-butyl-arylazopyrazole butyl sulfonate (butyl-AAP-C4S) surfactant that can change its structure at the air-water interface by E/Z photo-isomerization in an unprecedented way. Large and reversible changes in surface tension (Δγ = 27 mN m-1) and surface excess (ΔΓ > 2.9 μmol m-2) demonstrate superior performance of the butyl-AAP-C4S amphiphile to that of existing ionic surfactants. Neutron reflectometry and vibrational sum-frequency generation spectroscopy reveal that these large changes are caused by an unexpected monolayer-to-bilayer transition. This exceptional behavior is further shown to have dramatic consequences at larger length scales as highlighted by applications like the light-triggered collapse of aqueous foam which is tuned from high (>1 h) to low (<10 min) stabilities and light-actuated particle motion via Marangoni flows.

Mini-Generator Based on Reciprocating Vertical Motions Driven by Intracorporeal Energy

Most implantable devices rely on a power supply from batteries and require replacement surgeries once the batteries run low. Mini-generators that harvest intracorporeal energy available in the human body are promising replacements of batteries and prolong the lifetime of implantable devices, thus reducing surgery pain, risks, and cost. Although various sources of energy available in the human body are used for electricity generation using piezoelectric and triboelectric materials or intravascular turbines, concerns about material durability or thrombus risks remain, and developing novel strategies to fabricate a mini-generator to harvest the intracorporeal energy is still challenging. Herein, a mini-generator system is designed by exporting the systolic/diastolic blood pressure from the femoral artery of a sheep to trigger the pressure-responsive reciprocating vertical motions of a conductor. By applying a magnetic field, an induced voltage of 0.32 V and a stable output power of 13.86 µW are obtained, which is promising to power a state-of-the-art pacemaker (8-10 µW). The noncontact electricity generation strategy provides a novel avenue to sustainable power supply for implantable devices.