Single-particle placement via self-limiting electrostatic gating

Abstract

This letter reports single-particle placement in which exactly one nanoparticle is electrostatically guided and placed onto a target location. Using an ∼20 nm Au nanoparticle colloid as a model system, we demonstrate that self-limiting interactions between a charged nanoparticle and a charged substrate surface are extremely effective in positioning a single Au nanoparticle on each target location. Detailed theoretical calculations revealed that the self-limiting capability in the nanoparticle positioning is due to an increase in the free energy barrier after the first nanoparticle lands on a target position, effectively blocking the approach of other nanoparticles.

Nanoparticle assembly enabled by EHD-printed monolayers

“…For Au-MHA devices, based on the previously established routes to single-particle assembly 7,8 , 50 nm of Au (with Cr adhesion) was thermally evaporated onto the surface under high vacuum. These surfaces were spin-coated at 4000 rpm with poly(methyl methacrylate) (PMMA) to a 100 nm thickness, which was then patterned by EBL.…”

“…Burgeoning methods of additive nanomanufacturing offer a potential solution to this problem, by enabling the top-down integration of existing devices with nanomaterials [1][2][3][4][5][6] , whose properties have demonstrable applications in novel areas of biosensing 4 , single-electron transport 5 , quantum phenomena 6 , and more. These materials can be made to self-assemble into desired configurations via many driving forces, from electrophoresis [7][8][9][10] , DNA-linkages 11,12 and geometrical interactions [13][14][15] . Controlling when and where such self-assembly occurs requires lithography, however, which to integrate with modern device designs must meet sub-100 nm resolution as standard.…”

Additive nanomanufacturing – A review

“…This is comparable to the accuracy of the selfassembly approach to single-particle placement. 149 The use of these nanoapertures also benefits from a low increase in temperature of approximately 0.3 K, which helps limit the attraction of multiple particles to the aperture by thermophoresis and avoids damaging biological entities during manipulation. Following a similar design practice 50 nm polystyrene beads have recently been trapped in a nanoaperture on an optical fibre and manipulated in suspension over several microns 150 ( See FIG.…”

“…This is an extremely impressive result considering that the diameter of the gate is almost 7 times larger than that of the particle it isolated and could have been even better if the lithographic definition of the gates were more accurate. It is entirely likely that a combination of the techniques of the gating mechanism 149 and transfer printing 163,164 can be combined for electrically directed assembly; 165 incorporated into a probe configuration, this may be useful for the 3D printing of individual nanoparticles. In conclusion, single particle placement is able to build structures ranging from individual atoms up to hundreds of nanometres, but so far the throughput is very low and only useful for basic research and proof of concept designs.…”

“…163 Unfortunately capillary assembly makes it hard to control the exact location that nanoparticles will adhere to, which is very important to positioning particles in desired configurations. A more accurate method of isolating nanoparticles may instead be achieved by electrostatic interactions between a colloid and self-assembled monolayers 149 ( See FIG. 18).…”