Se-Chul Park

Effective localized collection and identification of airborne species through electrodynamic precipitation and SERS-based detection

Various nanostructured sensor designs currently aim to achieve or claim single molecular detection by a reduction of the active sensor size. However, a reduction of the sensor size has the negative effect of reducing the capture probability considering the diffusion-based analyte transport commonly used. Here we introduce and apply a localized programmable electrodynamic precipitation concept as an alternative to diffusion. The process provides higher collection rates of airborne species and detection at lower concentration. As an example, we compare an identical nanostructured surfaced-enhanced Raman spectroscopy sensor with and without localized delivery and find that the sensitivity and detection time is improved by at least two orders of magnitudes. Localized collection in an active-matrix array-like fashion is also tested, yielding hybrid molecular arrays on a single chip over a broad range of molecular weights, including small benzenethiol (110.18 Da) and 4-fluorobenzenethiol (128.17 Da), or large macromolecules such as anti-mouse IgG (~150 kDa).

A First Implementation of an Automated Reel-to-Reel Fluidic Self-Assembly Machine

A first automated reel-to-reel fluidic selfassembly process for macroelectronic applications is reported. This system enables high-speed assembly of semiconductor dies (15 000 chips per hour using a 2.5 cm-wide web) over large-area substrates. The optimization of the system (>99% assembly yield) is based on identification, calculation, and optimization of the relevant forces. As an application, the production of a solid-state lighting panel is discussed, involving a novel approach to apply a conductive layer through lamination.

Effective collection and detection of airborne species using SERS-based detection and localized electrodynamic precipitation.

Three different delivery concepts (standard diffusion, global electrodynamic precipitation, and localized nanolens-based precipitation) and three different SERS enhancement layers (a silver film, a nanolens-based localized silver nanoparticle film, and the standard AgFON) are compared. The nanolens concept is applied to increase the SERS signal: a factor of 633, when compared to a standard mechanism of diffusion, is observed.

Self-Assembly and Self-Tiling: Integrating Active Dies Across Length Scales on Flexible Substrates

This paper reports on recent progress in the field of directed self-assembly, wherein discrete inorganic semiconductor device components are assembled on flexible substrates, and compares these results with prior work. The research aims to develop self-assembly-based chiplet assembly processes that can extend minimal die sizes and throughput beyond what is currently possible with robotic pick and place methods. This manuscript concentrates on self-assembly that is driven by the reduction of surface free energy between liquid solder-coated areas on a substrate and metal-coated contacts on semiconductor dies that act as binding sites. Scaling prior results to sub-100 micrometer-sized components has required a transition to a new self-assembly platform. Specifically, recent work has moved from a drum delivery concept to a new scheme that uses a stepwise reduction of interfacial free energy at a triple interface between oil, water, and a penetrating solder-patterned substrate to introduce components. Finally, this paper also discusses design rules to produce highly periodic “self-tiled” domains on rigid, flexible, and curved substrates. We describe discrete, self-tiled, and microconcentrator-augmented solar cell modules as applications that are fault tolerant and reduce the amount of Si material used by up to a factor of 22 when compared to conventional cells.

Approaching Gas Phase Electrodeposition: Process and Optimization to Enable the Self‐Aligned Growth of 3D Nanobridge‐Based Interconnects

A nanowire bonding process referred to as gas-phase electrodeposition is reported to form nanobridge-based interconnects. The process is able to grow free-standing point-to-point electrical connections using metallic wires. As a demonstration, programmable interconnects and an interdigitated electrode array are shown. The process is more material efficient when compared with conventional vapor deposition since the material is directed to the point of use.

Millimeter Thin and Rubber‐Like Solid‐State Lighting Modules Fabricated Using Roll‐to‐Roll Fluidic Self‐Assembly and Lamination

A millimeter thin rubber-like solid-state lighting module is reported. The fabrication of the lighting module incorporates assembly and electrical connection of light-emitting diodes (LEDs). The assembly is achieved using a roll-to-roll fluidic self-assembly. The LEDs are sandwiched in-between a stretchable top and bottom electrode to relieve the mechanical stress. The top contact is realized using a lamination technique that eliminates wire-bonding.

Approaching Roll-to-Roll Fluidic Self-Assembly: Relevant Parameters, Machine Design, and Applications

This paper presents the implementation of an automated roll-to-roll fluidic self-assembly system based on the surface tension driven self-assembly with applications in the field of macroelectronics. The reported system incorporates automated agitation, web motion, component dispensing, and recycling. The process enables the assembly and electrical connection of semiconductor dies/chips in a continuous and parallel fashion over wide area substrates. At present, the method achieves an assembly rate of 15000 chips per hour and an assembly yield exceeding 99%, testing assembly of standard square-shaped dies, 300-1000 μm size. Scaling the system to any desired throughput is possible due to the parallel manner of selfassembly. The identification and the modeling of the relationship between process parameters and forces have been studied and experimentally verified by testing the effect of the web angle, agitation on assembly, and detachment rates. As an application, we demonstrate the realization of a solid-state lighting module. This particular application requires the assembly of a conductive multilayer sandwich structure, which is achieved by combining the introduced assembly process with a novel lamination step.