|Title||Localized 3-D Functionalization of Bionanoreceptors on High-Density Micropillar Arrays via Electrowetting.|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Chu, S, Winkler, TE, Brown, ADegen, Culver, JN, Ghodssi, R|
|Date Published||2018 Jan 04|
In this work, we introduce an electrowetting-assisted 3-D biofabrication process allowing both complete and localized functionalization of bionanoreceptors onto densely arranged 3-D microstructures. Integration of biomaterials with three-dimensional (3-D) microdevice components offers exciting opportunities for communities developing miniature bioelectronics with enhanced performances and advanced modes of operation. However, most biological materials are stable only in properly conditioned aqueous solutions, thus the water-repellent properties exhibited by densely arranged micro-/nano- structures (widely known as the Cassie-Baxter state) represent a significant challenge to biomaterial integration. Here, we first investigate such potential limitations using cysteine-modified Tobacco mosaic virus (TMV1cys) as a model bionanoreceptor and a set of Au-coated Si-micropillar arrays (µPAs) of varying densities. Further, we introduce a novel biofabrication system adopting electrowetting principles for the controlled localization of TMV1cys bionanoreptors on densely arraged µPAs. Contact angle analysis and SEM characterizations provide clear evidence to indicate structural hydrophobicity as a key limiting factor for 3-D biofunctionalization, and for electrowetting as an effective method to overcome this limitation. The successful 3-D biofabrication is confirmed using SEM and fluorescence microscopy that show spatially controlled and uniform assemblies of TMV1cys on µPAs. The increased density of TMV1cys per device foot-print produces a 7-fold increase in fluorescence intensity attributed to the µPAs when compared to similar assemblies on planar substrates. Combined, this work demonstrates the potential of electrowetting as a unique enabling solution for the controlled and efficient biofabrication of 3-D patterned micro/nano domains.