The use of microfabricated cantilevers as bioaffinity sensors was investigated. Since many bioaffinity interactions involve proteins as receptors, we conducted studies of the magnitude, kinetics, and reversibility of surface stresses caused when common proteins interact with microcantilevers (MCs) with nanostructured (roughened) gold surfaces on one side. Exposure of nanostructured, unfunctionalized MCs to the proteins immunoglobulin G and bovine serum albumin (BSA) resulted in reversible large tensile stresses, whereas MCs with smooth gold surfaces on one side produced reversible responses that were considerably smaller and compressive. The response magnitude for nanostructured MCs exposed to BSA is shown to be concentration dependent, and linear calibration over the range of 1-200 mg/L is demonstrated. Stable, reusable protein bioaffinity phases based on unique enantioselective antibodies are created by covalently linking monoclonal antibodies to nanostructured MC surfaces. The direct (label-free) stereoselective detection of trace amounts of an important class of chiral analytes, the alpha-amino acids, was achieved based on immunomechanical responses involving nanoscale bending of the cantilever. The temporal response of the cantilever (delta deflection/delta time) is linearly proportional to the analyte concentration and allows the quantitative determination of enantiomeric purity up to an enantiomeric excess of 99.8%. To our knowledge, this is the first demonstration of chiral discrimination using highly scalable microelectromechanical systems.

Polymer-nano-metallic-particle composites have demonstrated technological potential due to their unique optical and electrical properties. Herein, we report on composites prepared via physical vapor deposition of silver metal onto pliable poly(dimethylsiloxane) (PDMS) polymer. Rapid Ag diffusion and nano-metallic-particle formation in a phase-separated surface layer of the PDMS creates unique sub-surface-based composites whose properties vary based on rate of deposition and average Ag thickness. Additionally, nanometallic-particle spacing can be altered with fair reproducibility and reversibility by physically manipulating the Ag-PDMS composite. The optical properties of the materials are studied by visible wavelength optical extinction spectrometry and surface-enhanced Raman scattering (SERS), including studies performed during physical manipulation. Direct current (DC) conductivity measurements were made during Ag deposition to study percolation conditions for the materials. Depth-profiling was performed by X-ray photoelectron spectrometry. Sample Raman spectral data collected with the composite as a SERS substrate are included. A practical technological characteristic of these composite materials arises from their potential to be molded into functional devices.

We have observed Shubnikov-de Haas and de Haas-van Alphen effects in the single crystals of three dimensional Dirac semimetal Cd3As2 upto to 50 K, traceable at field as low as 2 T and 1 T, respectively. The values of Fermi wave vector, Fermi velocity, and effective cyclotron mass of charge carrier, calculated from both the techniques, are close to each other and match well with the earlier reports. However, the de Haas-van Alphen effect clearly reflects the existence of two different Fermi surface cross-sections along certain direction and a non-trivial Berry's phase which is the signature of 3D Dirac Fermion in Cd3As2.