Fast chemical imaging at high spatial resolution by laser ablation inductively coupled plasma mass spectrometry.

In recent years, chemical imaging was prognosticated to become one of the key analytical applications for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). However, moderate spatial resolution and the associated measurement time required for a larger sampling area, have restricted this versatile, high sensitivity technique from being routinely used in two-dimensional chemical imaging. This work describes the development and investigation of a low dispersion sample chamber (tube cell), which allows improvement of the imaging capabilities by reduction of the single LA shot duration to 30 ms (full width at 1% maximum). The new tube cell is based on a constant laminar flow and a well-controlled delivery of the laser-ablated aerosol into the transport system, leading to minimized tailing of the aerosol washout and helping to separate the signals even at repetition rates as high as 20-30 Hz. To demonstrate the improved imaging capabilities, microstructured metallic thin film patterns were analyzed at a spatial resolution of a few micrometers. The LA-ICP-MS results obtained were comparable to Synchrotron-based micro-X-ray fluorescence (SR-microXRF). The suitability of the newly designed cell for multielement acquisitions was demonstrated using a simultaneous ICP-Mattauch-Herzog-MS. Finally, the novel laser ablation cell was applied to image the distribution of a metal-tagged biomarker in a thin section of breast cancer tissue. This application demonstrates that the technique is able to produce subcellular (~1 µm) spatial resolution, which is crucial for morphological assessment in cancer diagnostics.

Sequential printing by laser-induced forward transfer to fabricate a polymer light-emitting diode pixel.

Patterned deposition of polymer light-emitting diode (PLED) pixels is a challenge for electronic display applications. PLEDs have additional problems requiring solvent orthogonality of different materials in adjacent layers. We present the fabrication of a PLED pixel by the sequential deposition of two different layers with laser-induced forward transfer (LIFT), a "dry" deposition technique. This novel use of LIFT has been compared to "normal" LIFT, where all the layers are transferred in a single step, and a conventional PLED fabrication process. For the sequential LIFT, a 50-nm film of an alcohol-soluble polyfluorene (PFN) is transferred onto a receiver with a transparent anode, before an aluminum cathode is transferred on top. Both steps use a triazene polymer dynamic release layer and are performed in a medium vacuum (1 mbar) across a 15 µm gap. The rough morphologies of the single-layer PFN pixels and the PLED device characteristics have been investigated and compared to both bilayer Al/PFN pixels fabricated by normal LIFT and conventionally fabricated devices. The functionality of the sequential LIFT pixels (0.003 cd/A, up to 200 mA/cm(2), at 30-40 V) demonstrates the suitability of LIFT for sequential patterned printing of different thin-film layers.