A novel platform for ultrasensitive and matrix-free laser desorption/ionization mass spectrometry (LDI-MS) based on nanofilament silicon surfaces is proposed. Currently, the sensitivity and overall functionality of matrix-free LDI-MS performed on porous silicon (pSi) chips are limited by a number of factors imposed by standard pSi substrates. In this proposal, we seek to address these issues through the development of novel silicon nanofilament substrates fabricated using metal-assisted oxidative etching and reactive-ion etching, with electrowetting used to provide dynamic control over surface hydrophobicity. This feature will allow switching of the surfaces from a superhydrophobic state to a strongly hydrophilic state, allowing for complete wetting of the nanofilaments for optimal sample deposition while limiting sample dispersion and providing a method to achieve on-target sample concentration, thereby enabling routine detection limits of 10-100 zmol (10-20 to 10-19 mol) for complex peptide samples. [unreadable] [unreadable] PUBLIC HEALTH RELEVANCE: The analysis of proteins from biological samples is enabling advances in the treatment and diagnosis of disease. This project addresses the development of an ultrasensitive nanotechnology-based platform which can improve the ability to perform protein analysis from limited samples such as tissue biopsies. [unreadable] [unreadable] [unreadable]