Figure 1. Overview of the CaTCh FISH platform.

a. Circulating tumor cells (CTCs) are shed from the primary tumor and circulate in the blood. Due to their scarcity relative to blood cells and their heterogeneous biomarker expression, CTCs are difficult to isolate and analyze. b. Schematic of the CaTCh FISH workflow, in which whole blood is isolated is isolated, CTCs are enriched through Track Etched Magnetic MicroPOre (TEMPO)-mediated negative selection, and then molecularly characterized with single molecule RNA FISH, all in under an hour. Scale bars are 60 µm and 8 µm respectively. c. Higher resolution schematic illustrating the key components of the CatTCh FISH platform: the TEMPO filter and Turbo RNA FISH. d. A cross-section of the CaTCh FISH chip. e. The TEMPO filter is fabricated by coating track etched polycarbonate with a film of magnetic material (Ni₈₀Fe₂₀), enabling millions of micro-scale magnetic traps to act in parallel for selective, ultra-fast isolation. f. The TEMPO and TurboFISH components are incorporated into a single monolithic chip using laser micro-machined laminate microfluidics. g. Finite element simulations of magnetic field are used to design the TEMPO, such that the magnetic force can be measured and compared to the competing drag force (h). The pore has a diameter of 30 µm.