Geometry-induced electrostatic trapping of nanometric objects in a fluid

Charged and trapped Many fields would benefit from a simple and efficient method for trapping single atoms, molecules or particles — a task that remains fiendishly difficult when dealing with nanometre-sized objects in solution. Krishnan et al. now show that grooves and pockets etched into fluidic channels that acquire a charge on exposure to water act as highly effective electrostatic traps. They hold dissolved gold nanoparticles, polymer beads and lipid vesicles for up to several hours and without external intervention. Furthermore, their stiffness and stability are easily adjusted and they lend themselves to integration with other manipulation mechanisms. With further optimization, this trapping concept could even enable contact-free confinement of single proteins and nanoparticles, their sorting and fractionation, or assembly into high-density arrays.