Grating-coupled surface plasmon field-enhanced fluorescence spectroscopy (GC-SPFS) with optical bound/free (B/F) separation technique was developed by employing a highly directional fluorescence with polarization of surface plasmon-coupled emission (SPCE) to realize highly sensitive immunoassay regardless of the ligand affinity. A highly sensitive immunoassay system with GC-SPFS was constructed using a plastic sensor chip reproducibly fabricated in-house by nanoimprinting and applied to the quantitative detection of an anti-lysozyme single-domain antibody (sdAb), to compare conventional washing B/F separation with optical B/F separation. Differences in the affinity of the anti-lysozyme sdAb, induced by artificial mutation of only one amino acid residue in the variable domain were attributed to higher sensitivity than that of the conventional Biacore surface plasmon resonance (SPR) system. The detection limit (LOD; means of six replicates of the zero standard plus three standard deviations) of the GC-SPFS immunoassay with optical B/F separation, was estimated to be 1.2 ng/ml with the low-affinity ligand (mutant sdAb Y52A: K D level was of the order of 10 −7 ~ 10 −6 M) and was clearly improved as compared to that (LOD: 9.4 ng/ml) obtained with the conventional washing B/F separation. These results indicate that GC-SPFS with the optical B/F separation technique offers opportunities to re-evaluate low-affinity biomaterials that are neither fully utilized nor widespread, and could facilitate the creation of novel and innovative methods in drug and diagnostic development.

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Microtribology of silicon single crystals is one of the key technologies from the viewpoint of reliability of practical application in micro electro mechanical system MEMS . In the study, a silicon single crystal 100 wafer was scratched by a silicon single crystal tip under a very small loading force in various atmospheres and temperatures, which was characterized using an atomic force microscope. In air and water, the silicon single crystal tips were worn greatly. However, the morphology of the scratched wafer surface was quite different; in air the scratched area of the wafer surface was forming a terrace. In vacuum, the tips were worn slightly. In terms of the effects of temperature, the silicon single crystal softened at 473 K was worn. At 673 K, the silicon single crystal wafer was worn greatly and stick slip like phenomenon occurred between the silicon single crystals signi cantly softened. As a result, microtribology is affected by atmospheres or temperatures.