Deterministic lateral displacement (DLD) pillar arrays are an efficient technology to sort, separate and enrich micrometre-scale particles, which include parasites, bacteria, blood cells and circulating tumour cells in blood. However, this technology has not been translated to the true nanoscale, where it could function on biocolloids, such as exosomes. Exosomes, a key target of 'liquid biopsies', are secreted by cells and contain nucleic acid and protein information about their originating tissue. One challenge in the study of exosome biology is to sort exosomes by size and surface markers. We use manufacturable silicon processes to produce nanoscale DLD (nano-DLD) arrays of uniform gap sizes ranging from 25 to 235 nm. We show that at low Péclet (Pe) numbers, at which diffusion and deterministic displacement compete, nano-DLD arrays separate particles between 20 to 110 nm based on size with sharp resolution. Further, we demonstrate the size-based displacement of exosomes, and so open up the potential for on-chip sorting and quantification of these important biocolloids.

The authors demonstrate atomic layer etching of SiO 2 using a steady-state Ar plasma, periodic injection of a defined number of C 4 F 8 molecules, and synchronized plasma-based Ar þ ion bombardment. C 4 F 8 injection enables control of the deposited fluorocarbon (FC) layer thickness in the one to several Å ngstrom range and chemical modification of the SiO 2 surface. For low energy Ar þ ion bombardment conditions, the physical sputter rate of SiO 2 vanishes, whereas SiO 2 can be etched when FC reactants are present at the surface. The authors have measured for the first time the temporal variation of the chemically enhanced etch rate of SiO 2 for Ar þ ion energies below 30 eV as a function of fluorocarbon surface coverage. This approach enables controlled removal of Å ngstrom-thick SiO 2 layers. Our results demonstrate that development of atomic layer etching processes even for complex materials is feasible.

The uncontrolled development of nanoscale roughness during plasma exposure of polymer surfaces is a major issue in the field of semiconductor processing. In this paper, we investigated the question of a possible relationship between the formation of nanoscale roughening and the simultaneous introduction of a nanometer-thick, densified surface layer that is formed on polymers due to plasma damage. Polystyrene films were exposed to an Ar discharge in an inductively coupled plasma reactor with controllable substrate bias and the properties of the modified surface layer were changed by varying the maximum Ar + ion energy. The modified layer thickness, chemical, and mechanical properties were obtained using real-time in situ ellipsometry, x-ray photoelectron spectroscopy, and modeled using molecular dynamics simulation. The surface roughness after plasma exposure was measured using atomic force microscopy, yielding the equilibrium dominant wavelength and amplitude A of surface roughness. The comparison of measured surface roughness wavelength and amplitude data with values of and A predicted from elastic buckling theory utilizing the measured properties of the densified surface layer showed excellent agreement both above and below the glass transition temperature of polystyrene. This agreement strongly supports a buckling mechanism of surface roughness formation.

We introduce a method to fabricate solid-state nanopores with sub-20 nm diameter in membranes with embedded metal electrodes across a 200 mm wafer using CMOS compatible semiconductor processes. Multi-layer (metal-dielectric) structures embedded in membranes were demonstrated to have high uniformity (± 0.5 nm) across the wafer. Arrays of nanopores were fabricated with an average size of 18 ± 2 nm in diameter using a Reactive Ion Etching (RIE) method in lieu of TEM drilling. Shorts between the membrane-embedded metals were occasionally created after pore formation, but the RIE based pores had a much better yield (99%) of unshorted electrodes compared to TEM drilled pores (<10%). A double-stranded DNA of length 1 kbp was translocated through the multi-layer structure RIE-based nanopore demonstrating that the pores were open. The ionic current through the pore can be modulated with a gain of 3 using embedded electrodes functioning as a gate in 0.1 mM KCl aqueous solution. This fabrication approach can potentially pave the way to manufacturable nanopore arrays with the ability to electrically control the movement of single or double-stranded DNA inside the pore with embedded electrodes.