THz Detection of Biomolecules in Aqueous Environments—Status and Perspectives for Analysis Under Physiological Conditions and Clinical use

Bioanalytical THz sensing techniques have proven to be an interesting and viable tool for the label-free detection and analysis of biomolecules. However, a major challenge for THz bioanalytics is to perform investigations in the native aqueous environments of the analytes. This review recapitulates the status and future requirements for establishing THz biosensing as a complementary toolbox in the repertoire of standard bioanalytic methods. The potential use in medical research and clinical diagnosis is discussed. Under these considerations, this article presents a comprehensive categorization of biochemically relevant analytes that have been investigated by THz sensing techniques in aqueous media. The detectable concentration levels of ions, carbohydrates, (poly-)nucleotides, active agents, proteins and different biomacromolecules from THz experiments are compared to characteristic physiological concentrations and lower detection limits of state-of-the-art bioanalytical methods. Finally, recent experimental developments and achievements are discussed, which potentially pave the way for THz analysis of biomolecules under clinically relevant conditions.

     

Electrical and flexural anisotropy in freeze tape cast stainless steel porous substrates

Engineered metal foams have strong potential in applications such as fuel cell electrodes, sensors, variable springs, filtering media, and compositionally graded composite structures. In this study, the variation in mechanical and electrical properties was characterized in engineered porous metal foams with aligned porosity to ascertain the degree of anisotropy that can be induced in these substrates. Porous substrates were prepared by freeze tape casting of powdered ferritic stainless steel. After directional solidification of the slurry, the solvent was sublimed from ~ 1 mm thick tapes, yielding porous green metal compacts which were sintered in a protective atmosphere. The resulting disks exhibit long range ordered acicular pores with substantial anisotropy in the mechanical and electrical properties that is related to the cross sectional pore morphology and connectivity. DC conductivity testing revealed up to 61% variation depending on direction of measurement relative to the alignment of pores. Also, an 89% variation in flexural rigidity in relation to pore orientation was observed in identical disks.