Abstract: Being able to sense and quantify is ubiquitous to for instance, water monitoring and clinical diagnostics. There is a drive towards point-of-use analysis, which requires sensors and analytical microsystems. Current point-of-use analysis based on lateral flow devices provide qualitative and at best semi-quantitative information. Label-free optical sensors based on refractive index measurements can overcome this limitation. In this presentation, I will discuss some of our research on leaky waveguide (LW) sensors and microsystems for clinical diagnostics.