Highly localized chemical sampling at sub-second temporal resolution enabled with a silicon nanodialysis platform at exceedingly slow flows.

Microdialysis (MD) is a versatile and powerful technique for chemical profiling of biological tissues and is widely used for quantification of neurotransmitters, neuropeptides, metabolites, biomarkers, and drugs in the central nervous system as well as in dermatology, ophthalmology, and in pain research. However, MD performance is severely limited by fundamental tradeoffs between chemical sensitivity, spatial resolution, and temporal response. Here, by using wafer-scale silicon microfabrication, we develop and demonstrate a nanodialysis (ND) sampling probe that enables highly localized chemical sampling with 100μm spatial resolution and sub-second temporal resolution at high recovery rates.

Enhancement of faradaic current in an electrochemical cell integrated into silicon microfluidic channels.

Implantable electrochemical sensors enable fast and sensitive detection of analytes in biological tissue, but are hampered by bio-foulant attack and are unable to be recalibrated in-situ. Herein, an electrochemical sensor integrated into ultra-low flow (nL/min) silicon microfluidic channels for protection from foulants and in-situ calibration is demonstrated. The small footprint (5 μm radius channel cross-section) of the device allows its integration into implantable sampling probes for monitoring chemical concentrations in biological tissues.

Integrated silicon microfluidic chip for picoliter-scale analyte segmentation and microscale printing for mass spectrometry imaging.

A silicon single-chip microfluidics system that integrates microscale fluidic channels, an analyte segmentation device, and a nozzle for electrohydrodynamic-assisted printing is designed for hyphenation with MALDI mass spectrometry (MS) imaging. A miniaturized T-junction segments analytes into monodisperse picoliter oil-isolated compartments. The printing nozzle deposits generated droplets one-by-one into an array on a conductive substrate without splitting or coalescing.