High Anodic-Voltage Focusing of Charge Carriers in Silicon Enables the Etching of Regularly-Arranged Submicrometer Pores at High Density and High Aspect-Ratio.

The anodic dissolution of silicon in acidic electrolytes is a well-known technology enabling the silicon machining to be accurately controlled down to the micrometer scale in low-doped -type silicon electrodes. Attempts to scale down this technology to the submicrometer scale has shown to be challenging, though it premises to enable the fabrication of meso and nano structures/systems that would greatly impact the fields of biosensors and nanomedicine. In this work, we report on the electrochemical etching at high anodic voltages (up to 40 V) of two-dimensional regular arrays of millions pores per square centimeter (up to 30 × 10 cm) with sub-micrometric diameter (down to ~860 nm), high depth (up to ~40 μm), and high aspect-ratio (up to ~45) using low-doped -type silicon electrodes (resistivity 3-8 Ω cm).

Layer-by-layer biofunctionalization of nanostructured porous silicon for high-sensitivity and high-selectivity label-free affinity biosensing.

Nanostructured materials premise to revolutionize the label-free biosensing of analytes for clinical applications, leveraging the deeper interaction between materials and analytes with comparable size. However, when the characteristic dimension of the materials reduces to the nanoscale, the surface functionalization for the binding of bioreceptors becomes a complex issue that can affect the performance of label-free biosensors. Here we report on an effective and robust route for surface biofunctionalization of nanostructured materials based on the layer-by-layer (LbL) electrostatic nano-assembly of oppositely-charged polyelectrolytes, which are engineered with bioreceptors to enable label-free detection of target analytes.

Electrical Double Layer-Induced Ion Surface Accumulation for Ultrasensitive Refractive Index Sensing with Nanostructured Porous Silicon Interferometers.

Herein, we provide the first experimental evidence on the use of electrical double layer (EDL)-induced accumulation of charged ions (using both Na and K ions in water as the model) onto a negatively charged nanostructured surface (e.g., thermally growth SiO)-Ion Surface Accumulation, ISA-as a means of improving performance of nanostructured porous silicon (PSi) interferometers for optical refractometric applications.

Femtomole Detection of Proteins Using a Label-Free Nanostructured Porous Silicon Interferometer for Perspective Ultrasensitive Biosensing.

Nanostructured porous silicon (PS) is a promising material for label-free optical detection of biomolecules, though it currently suffers of limited clinical diagnostic applications due to insufficient sensitivity. In this regard, here we introduce an ultrasensitive and robust signal processing strategy for PS biosensors that relies on the calculation of the average value over wavelength of spectral interferograms, namely IAW, obtained on PS interferometer by subtraction (wavelength by wavelength) of reflection spectra acquired after adsorption of biomolecules inside the nanopores from a reference reflection spectrum recorded in acetate buffer. As a case study, we choose to monitor bovine serum albumin (BSA) unspecific adsorption, which has been often employed in the literature as a model for proof-of-concept studies of perspective biosensing applications.

Sub-parts per million NO2 chemi-transistor sensors based on composite porous silicon/gold nanostructures prepared by metal-assisted etching.

Surface doping of nano/mesostructured materials with metal nanoparticles to promote and optimize chemi-transistor sensing performance represents the most advanced research trend in the field of solid-state chemical sensing. In spite of the promising results emerging from metal-doping of a number of nanostructured semiconductors, its applicability to silicon-based chemi-transistor sensors has been hindered so far by the difficulties in integrating the composite metal-silicon nanostructures using the complementary metal-oxide-semiconductor (CMOS) technology. Here we propose a facile and effective top-down method for the high-yield fabrication of chemi-transistor sensors making use of composite porous silicon/gold nanostructures (cSiAuNs) acting as sensing gate.

A minimally invasive microchip for transdermal injection/sampling applications.

The design, fabrication, and characterization of a minimally invasive silicon microchip for transdermal injection/sampling applications are reported and discussed. The microchip exploits an array of silicon-dioxide hollow microneedles with density of one million needles cm(-2) and lateral size of a few micrometers, protruding from the front-side chip surface for one hundred micrometers, to inject/draw fluids into/from the skin. The microneedles are in connection with independent reservoirs grooved on the back-side of the chip.

Fibrillogenesis of human β2 -microglobulin in three-dimensional silicon microstructures.

The authors describe the interaction of biological nanostructures formed by β(2) -microglobulin amyloid fibrils with three-dimensional silicon microstructures consisting in periodic arrays of vertical silicon walls (≈3 μm-thick) separated by 50 μm-deep air gaps (≈5 μm-wide). These structures are of great interest from a biological point of view since they well mimic the interstitial environment typical of amyloid deposition in vivo. Moreover, they behave as hybrid photonic crystals, potentially applicable as optical transducers for label-free detection of the kinetics of amyloid fibrils formation.