Design of a Novel, Inexpensive COIFM Using the DVD Optical Pickup Unit for Nanoscale Water Researches

Water is one of the most vital substances on Earth. Over the past twenty years, we have made a groundbreaking discovery known as 'self-assembled water chains' by inventing a unique tool called the cantilever-based optical interfacial force microscope (COIFM) and applying it to water research. The COIFM is capable of measuring forces as a function of distance, effectively addressing the 'snap-to-contact' issue that plagues conventional atomic force microscopy (AFM). It employs a force-feedback scheme to eliminate tip deflection while maintaining a high level of sensitivity. Despite the significant discovery of this new water structure using this innovative tool, the current COIFM system remains uncommercialized due to the high cost and bulkiness of the AFM equipment it relies on. In an effort to bring this system to the market, we have designed a novel, cost-effective COIFM that incorporates a digital versatile disk (DVD) optical pickup unit (OPU). This DVD OPU offers several outstanding features, including lightweight and compact dimensions without compromising force sensitivity due to its unique force sensing technique called the 'astigmatic' method. We have built an adapter to integrate the DVD OPU with the existing AFM scanner using 3-D printing technology. This DVD-OPU-based force sensing module will facilitate the commercialization of the COIFM system by being compatible with commercially available AFMs, making it affordable for both worldwide AFM users and nanoscale water researchers.