2D Cantilever Array with Fixed Geometries and Varying Spring Constants for Life Science Applications

We present 2D cantilever arrays for parallel AFM and their fabrication process using a silicon nitride cantilever with molded tip as the base element of the array. They are designed either for (i) force indentation onto living cells and stiffness mapping, or (ii) cell-to-cell adhesion test applications. The former needs the cantilevers with 0.03 N/m and the tip radius 50 – 200 nm. The latter requires 3 N/m and 2500 nm, respectively. The technique to fabricate those cantilever arrays with different specifications, without significantly changing the fabrication process, is the core of this work. The parallel AFM system itself has been developed and presented elsewhere (M. Favre, et al., Journal of Molecular Recognition, vol. 24, pp. 446-452, 2011). To obtain cantilevers with different spring constants from a wafer, V-grooves structures along the cantilevers were introduced in the cantilever design. An analytical model and an FEA simulation confirmed that the spring constant can be varied up to two decades by changing the V-groove depth. To obtain a large tip radius required for cell handling, we developed a mold enlarging/rounding step and obtained a tip with a radius up to 4 μm.