Automatically Aligned and Environment-Friendly Twisted Stacking Terahertz Chiral Metasurface with Giant Circular Dichroism for Rapid Biosensing

Chiral metasurfaces are capable of generating a huge superchiral field, which has great potential in optoelectronics and biosensing. However, the conventional fabrication process suffers greatly from time consumption, high cost, and difficult multilayer alignment, which hinder its commercial application. Herein, we propose a twisted stacking carbon-based terahertz (THz) chiral metasurface (TCM) based on laser-induced graphene (LIG) technology. By repeating a two-step process of sticking a polyimide film, followed by laser direct writing, the two layers of the TCM are aligned automatically in the fabrication. Laser manufacturing also brings such high processing speed that a TCM with a size of 15 × 15 mm can be prepared in 60 s. In addition, due to the greater dissipation of LIG than that of metals in the THz band, a giant circular dichroism (CD) of +99.5 to -99.6% is experimentally realized. The THz biosensing of bovine serum albumin enhanced by the proposed TCMs is then demonstrated. A wide sensing range (0.5-50 mg mL^-1) and a good sensitivity [ΔCD: 2.09% (mg mL^-1)^-1, Δf: 0.0034 THz (mg mL^-1)^-1] are proved. This LIG-based TCM provides an environment-friendly platform for chiral research and has great application potential in rapid and low-cost commercial biosensing.