Drawing inspiration from the adhesion abilities of a leaf beetle found in nature, we have engineered a switchable adhesion device. The device combines two concepts: The surface tension force from a large number of small liquid bridges can be significant (capillaritybased adhesion) and these contacts can be quickly made or broken with electronic control (switchable). The device grabs or releases a substrate in a fraction of a second via a low-voltage pulse that drives electroosmotic flow. Energy consumption is minimal because both the grabbed and released states are stable equilibria that persist with no energy added to the system. Notably, the device maintains the integrity of an array of hundreds to thousands of distinct interfaces during active reconfiguration from droplets to bridges and back, despite the natural tendency of the liquid toward coalescence. We demonstrate the scaling of adhesion strength with the inverse of liquid contact size. This suggests that strengths approaching those of permanent bonding adhesives are possible as feature size is scaled down. In addition, controllability is fast and efficient because the attachment time and required voltage also scale down favorably. The device features compact size, no solid moving parts, and is made of common materials.bioinspired design | controlled wet adhesion | electroosmotic pump | leaf beetle | volume scavenging

Battery-like supercapacitors feature high power and energy densities as well as long-term capacitance retention. The utilized capacitor electrodes are thus better to have large surface areas, high conductivity, high stability, and importantly be of binder free. Herein, vertically 3-/4-), respectively For assembled two-electrode symmetrical supercapacitor devices, the capacitances of EDLC and PC devices reach 30 and 48 mF cm -2 at 10 mV s -1 , respectively.They remain constant even after 10 000 cycles.

Supercapacitors supply high power densities but suffer from low energy densities and small specific capacitances. The design and implementation of unique capacitor electrodes are expected to overcome these challenges. Herein, flexible diamond fibers (a fibrous core/shell structure of diamond/carbon fibers) are produced through overgrowing conductive carbon fibers core with a thin boron‐doped diamond film as a shell using a chemical vapor deposition technique. The resultant fibers combine the properties of boron‐doped diamond with those of carbon fibers. This allows these binder‐free diamond fibers to be employed as the positive electrode in the fabrication of zinc‐ion supercapacitors. Together with a negative electrode fabricated from zinc nanosheet coated diamond fibers, this diamond supercapacitor delivers a high and stable specific capacitance. More importantly, it delivers high gravimetric and volumetric energy and power densities, even under severe bending states. The performance of this flexible supercapacitor is superior to previous diamond and carbon fiber‐based supercapacitors. Such flexible diamond supercapacitors are promising energy storage devices for various flexible electronics.

The small scales associated with lab-on-a-chip technologies lend themselves well to capillarity-dominated phenomena. We demonstrate a new capillarity-dominated system where two adjoining ferrofluid droplets can behave as an electronically-controlled oscillator or switch by an appropriate balance of magnetic, capillary, and inertial forces. Their oscillatory motion can be exploited to displace a surrounding liquid (akin to an axial piston pump), forming electromagnetic "liquid pistons." Such ferrofluid pistons can pump a precise volume of liquid via finely tunable amplitudes (cf. pump stroke) or resonant frequencies (cf. pump speed) with no solid moving parts for long-term operation without wear in a small device. Furthermore, the rapid propagation of electromagnetic fields and the favorable scaling of capillary forces with size permit micron sized devices with very fast operating speeds (∼kHz). The pumping dynamics and performance of these liquid pistons is explored, with experimental measurements showing good agreement with a spherical cap model. While these liquid pistons may find numerous applications in micro- and mesoscale fluidic devices (e.g., remotely activated drug delivery), here we demonstrate the use of these liquid pistons in capillarity-dominated systems for chip-level, fast-acting adaptive liquid lenses with nearly perfect spherical interfaces.

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