Electron Irradiation Driven Nanohands for Sequential Origami

Abstract

Sequence plays an important role in self-assembly of 3D complex structures, particularly for those with overlap, intersection, and asymmetry. However, it remains challenging to program the sequence of self-assembly, resulting in geometric and topological constrains. In this work, a nanoscale, programmable, self-assembly technique is reported, which uses electron irradiation as "hands" to manipulate the motion of nanostructures with the desired order. By assigning each single assembly step in a particular order, localized motion can be selectively triggered with perfect timing, making a component accurately integrate into the complex 3D structure without disturbing other parts of the assembly process. The features of localized motion, real-time monitoring, and surface patterning open the possibility for the further innovation of nanomachines, nanoscale test platforms, and advanced optical devices

Plasmonic 3D Self‐Folding Architectures via Vacuum Microforming

“…The concept of folding 2D patterns into desired 3D microarchitectures provides a highly promising strategy to meet such demands, for one can readily incorporate various planar processes that are well established in semiconductor technologies such as photolithography, deposition, and etching on different length scales. Realizing a 3D self‐folding microarchitecture usually contains a few sequential steps, where 2D patterns are fabricated first, followed by the self‐folding process triggered by various external forces, such as capillary force, [ 6–8 ] magnetic force, [ 9,10 ] and ion/electron bombardment, [ 11–13 ] as well as internal force from the strain gradient which can stem from cross‐linking gradient, [ 14 ] or the mismatch of mechanical properties in multilayer stacks. [ 15–17 ] To name a few examples, by applying an external dynamically changed magnetic field, microbird that can flap its wings [ 9 ] and soft platelets that can achieve controlled locomotion [ 4 ] were demonstrated, respectively; exploiting the strain gradient in between various materials strategically distributed along the vertical direction, polyhedrons with controllable sizes were successfully fabricated.…”

Self-Assembled 3D Nanosplit Rings for Plasmon-Enhanced Optofluidic Sensing

“…After being released from silicon (Si) substrate, the 2D patterns are irradiated by electron streams. The electron irradiation (5 kV) enables the transformation of amorphous Al 2 O 3 into crystal Al 2 O 3 , which is associated with significant volume reduction . The volume change induces tensile and compression stress in the Al 2 O 3 /Cr layers, allowing the bilayer to curve up (Figure c).…”

“…A clear nanogap is observed in the self-assembled nanocylinder when analyzing their backscattered electron (BSE) image (Figure g) and zoomed in image (Figure h). As the formation of the nanogap is self-stopped, the size of the nanogap is uniform and easily controlled (Figure S1) using an in situ monitored self-assembly process . It should be noted that the size of the cylinder can be easily tuned to adjust the resonant frequency of NSRs by changing the dimension of the 2D patterns.…”

“…The hybrid 3D plasmonic sensor (nanocylinders with NSRs) was fabricated through an electron irradiation induced selfassembly process (Figure 1b,c). 31 The 2D pattern before assembly consists of two components: an actuation bilayer of 1 nm thick chromium (Cr) and 5 nm thick aluminum oxide (Al 2 O 3 ) and a metallic pattern of 5 nm gold (Au) (Figure 1d,e). After being released from silicon (Si) substrate, the 2D patterns are irradiated by electron streams.…”

“…The electron irradiation (5 kV) enables the transformation of amorphous Al 2 O 3 into crystal Al 2 O 3 , which is associated with significant volume reduction. 31 The volume change induces tensile and compression stress in the Al 2 O 3 /Cr layers, allowing the bilayer to curve up (Figure 1c). Once the two edges of the actuating bilayer touch, the curving process self-stops and forms nanocylinders (Figure 1f−i).…”