Micro Fabricated MEMS Colorimetric Devices to Measure Zika-Induced Residual Stress and Mass Loading

Microfabricated silicon nitride cantilever beams, with gold disks and triangles were used to study and quantify residual stresses generated by binding with the thiol end groups of Zika aptamers and then with Zika. Binding with aptamers and Zika generated large tensile residual stresses ~ 53 MPa that deflected the beams and changed their reflective color. It also caused the triangular gold patches to detach from their nitride substrates affecting the substrates' “golden” color. Dynamic measurements of the nitride beams' vibrations were used to measure mass loading by Zika with the sensitivity of 2 kHz/ng. The residual stress built-up due to binding with Zika in excess of 9 × 10⁴ Zika/beam caused nitride beams to buckle. Zika-induced residual stress measured using the triangular patches was 96 MPa. Large-scale cellulose acetate beams were then used to observe the residual stresses caused by 20 nm gold layer (0.24 MPa), aptamers (0.3 MPa), and then with Zika (0.5 MPa). Acetate beam displacement was used to “sense” Zika with 2 x 10^-6 μm/Zika sensitivity.