realized as a sharp tip with nanometersize apex attached to a micrometer-scale cantilever. In current SPM systems, tip and cantilever are usually structured in a dedicated microfabrication process before being manually mounted and aligned to a macroscopic optomechanical system for piezoelectric actuation and optical detection of sub-nanometer movements. This concept leads to rather bulky implementations and requires laborious operation, given that the tip is a wear part that has to be regularly exchanged and re-aligned to the read-out system. In addition, tip-cantilever geo metries are currently restricted by the underlying fabrication techniques, relying on 2D lithographic patterning and subsequent anisotropic etching. These techniques usually result in pyramidal tips with rather low aspect ratios, and the dimensions of the cantilever are often subject to fabrication tolerances that lead to variations of the resonance frequency of 30% or more. [10] Moreover, current SPM systems are often limited in scanning speed, which inhibits high-throughput characterization of large sample areas. This may be overcome by arrays of SPM cantilevers for parallel scanning, [11,12] but the scalability and integration density of current SPM schemes is limited by the fact that each cantilever must still be individually addressed by a dedicated actuator and sensor element of macroscopic dimension. Chiplevel integration of individually addressable cantilevers has been Scanning-probe microscopy (SPM) is the method of choice for high-resolution imaging of surfaces in science and industry. However, SPM systems are still considered as rather complex and costly scientific instruments, realized by delicate combinations of microscopic cantilevers, nanoscopic tips, and macroscopic read-out units that require high-precision alignment prior to use. This study introduces a concept of ultra-compact SPM engines that combine cantilevers, tips, and a wide variety of actuator and read-out elements into one single monolithic structure. The devices are fabricated by multiphoton laser lithography as it is a particularly flexible and accurate additive nanofabrication technique. The resulting SPM engines are operated by optical actuation and read-out without manual alignment of individual components. The viability of the concept is demonstrated in a series of experiments that range from atomic-force microscopy engines offering atomic step height resolution, their operation in fluids, and to 3D printed scanning near-field optical microscopy. The presented approach is amenable to wafer-scale mass fabrication of SPM arrays and capable to unlock a wide range of novel applications that are inaccessible by current approaches to build SPMs.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.
3D direct laser writing based on two-photon polymerization is considered as a tool to fabricate tailored probes for atomic force microscopy. Tips with radii of 25 nm and arbitrary shape are attached to conventionally shaped micro-machined cantilevers. Long-term scanning measurements reveal low wear rates and demonstrate the reliability of such tips. Furthermore, we show that the resonance spectrum of the probe can be tuned for multi-frequency applications by adding rebar structures to the cantilever.
Using two-photon lithography, we fabricate an ultra-compact atomic force microscope engine on the facet of a multi-core fiber. The AFM is optically actuated and read out, and it offers atomic step-height resolution in difficult-to-access areas.
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