A microfabricated low-cost Au nanotip pyramidal electrode array using anisotropic etching for enhanced performance of a glucose biosensor

We present the low-cost microfabrication of three-dimensional Au nanotip pyramidal electrode array by selective and anisotropic etching η-type Si in tetramethylammonium hydroxide (TMAH) solution. The influence of the TMAH etchant concentration and bath temperature on the on lithographically patterned Si etch rate was investigated. Using buffer oxidize etching technique of thermal oxide, sputtered metallic Au nanotip pyramidal electrode array are released from the resultant inverted pyramid Si master mold. The Au nanotip pyramidal electrode array with average size of 5.34 × 5.34 μm, pitch size as small as 198 nm, and individual tip diameter as small as 62 nm were successfully fabricated using a low-cost effective beaker chemistry method. Glucose oxidase (GOx) immobilized on the Au nanotip pyramidal electrode array retains its biocatalytic activity and offers a fast sensitive glucose quantification. The combination of Au nanotip pyramidal electrode array with GOx enhances the performance of the glucose biosensor. The fabricated glucose biosensor exhibits a linear dynamic response up to 18 mM glucose and a sensitivity of 122.5 μA cm^-2 mM^-1.