Trace detection of bio-molecules with large molecular weight using surface-enhanced Raman scattering (SERS) method is still challenging, because the troublesome treatment of SERS substrate using coupling or cross-linking agents is required. In this paper, we apply liquid interface assisted SERS (LI-SERS) method, which provides unique features of collection and self-immobilization of analyte molecules on the SERS substrate, to realize the label-free trace detection of bio-molecules with detection limits of pM ~ fM. Specifically, DNA discrimination and quantitative detection of β-Amyloid (Aβ) in trace-concentration are demonstrated to illustrate the ultrahigh sensitivity and versatility of the LI-SERS method.

Whispering gallery mode microtoroid optical resonators are one of the most sensitive and rapid optical sensors in existence. These sensors can detect extremely low analyte concentrations down to attomolar levels on the order of seconds. How these sensors have such a rapid response time even at these low concentrations is a question in the field. Here, we show that total analyte arrival and binding time can occur in seconds using flow visualization and finite-element simulations.

Biophysical properties (BPs) of a cell depend drastically on its physiological or pathological state. Thus, being able to accurately and non-invasively measure a set of cell BPs, that reflect these cellular states, is of major importance. To this end, we propose an approach that combines customized fluidic devices with digital holographic microscopy (DHM). Specifically, we have developed several low-cost 3D-printed millifluidic devices which when combined with DHM allow to measure in a controlled physiological environment specific cell BPs including intracellular refractive index, absolute cell volume, membrane flickering as well as cell elasticity and viscosity moduli.