Electrostatic tweezer for droplet manipulation

Abstract

Various physical tweezers for manipulating liquid droplets based on optical, electrical, magnetic, acoustic, or other external fields have emerged and revolutionized research and application in medical, biological, and environmental fields. Despite notable progress, the existing modalities for droplet control and manipulation are still limited by the extra responsive additives and relatively poor controllability in terms of droplet motion behaviors, such as distance, velocity, and direction. Herein, we report a versatile droplet electrostatic tweezer (DEST) for remotely and programmatically trapping or guiding the liquid droplets under diverse conditions, such as in open and closed spaces and on flat and tilted surfaces as well as in oil medium. DEST, leveraging on the coulomb attraction force resulting from its electrostatic induction to a droplet, could manipulate droplets of various compositions, volumes, and arrays on various substrates, offering a potential platform for a series of applications, such as high-throughput surface-enhanced Raman spectroscopy detection with single measuring time less than 20 s.

Light-induced charged slippery surfaces

“…Figure 2E shows that its light-induced peak-topeak charge density can rapidly reach as high as 1280 pC mm −2 in 0.5 s (fig. S9; see Supplementary Discussion 1.1), which is ~142 times higher than those on superhydrophobic surfaces and large enough to drive droplets (13,45). Turning off the NIR light irradiation reduces the local temperature and the thermal movements of P(VDF-TrFE) molecular chains, leading to the fast recovery of the P(VDF-TrFE) polarization and disappearance of free surface charges (fig.…”

Reconfigurable Magnetic Liquid Metal Robot for High-Performance Droplet Manipulation

“…Controllable droplet manipulation, such as capture, transport, merging, and mixing of droplets, plays a crucial role in various fields including chemical and biological analysis, − medical detection, , and biosensing . In order to achieve the efficient droplet manipulation, diverse external stimuli have been explored including surface acoustic wave, light, , magnetic field, , electric field, − and mechanical vibration. , Because of the advantages of noncontact, biocompatibility, and real-time control, the use of magnetic fields to manipulate droplets has attracted broad attention in recent years. Magnetic-actuated droplet manipulation can be roughly divided into two categories.…”

Effect of Surface Pre-Charging and Electric Field on the Contact Electrification between Liquid and Solid

“…The flow of liquid over a solid surface normally results in the solid surface being electrically charged. − Moreover, when the liquid flows over the charged solid surface again, it shows fascinating physical–chemical changes. This charged interface is widely employed in droplet manipulation, , energy conversion, − catalysis , and electrochemistry, , and so forth. However, almost all of these works have focused on the charged solid, while the charged liquid or both charged cases remain unexplored, which leads to an incomplete understanding of the solid–liquid interface.…”