The current nanofabrication techniques including electron beam lithography provide fabrication resolution in the nanometre range. The major limitation of these techniques is their incapability of arbitrary three-dimensional nanofabrication. This has stimulated the rapid development of far-field three-dimensional optical beam lithography where a laser beam is focused for maskless direct writing. However, the diffraction nature of light is a barrier for achieving nanometre feature and resolution in optical beam lithography. Here we report on three-dimensional optical beam lithography with 9 nm feature size and 52 nm two-line resolution in a newly developed two-photon absorption resin with high mechanical strength. The revealed dependence of the feature size and the two-line resolution confirms that they can reach deep sub-diffraction scale but are limited by the mechanical strength of the new resin. Our result has paved the way towards portable three-dimensional maskless laser direct writing with resolution fully comparable to electron beam lithography.

An ethoxylated bis-phenol-A dimethacrylate based photoresin BPE-100 of relatively high photosensitivity and modulus is used for the creation of sub-50 nm features. This is achieved by using the direct laser writing technique based on the single-photon photoinhibited polymerization. The super-resolution feature is realized by overlapping two laser beams of different wavelengths to enable the wavelength-controlled activation of photoinitiating and photoinhibiting processes in the polymerization. The increased photosensitivity of the photoresin promotes a fast curing speed and enhances the photopolymerization efficiency. Using the photoresin BPE-100, we achieve 40 nm dots for the first time in the super-resolution fabrication technique based on the photoinhibited polymerization, and a minimum linewidth of 130 nm. The influence of the power of the inhibiting laser and the exposure time on the feature size is studied and the results agree well with the prediction obtained from a simulation based on a non-steady-state kinetic model.

Micromanipulation and biological, material science, and medical applications often require to control or measure the forces asserted on small objects. Here, we demonstrate for the first time the microprinting of a novel fiber-tip-polymer clamped-beam probe micro-force sensor for the examination of biological samples. The proposed sensor consists of two bases, a clamped beam, and a force-sensing probe, which were developed using a femtosecond-laser-induced two-photon polymerization (TPP) technique. Based on the finite element method (FEM), the static performance of the structure was simulated to provide the basis for the structural design. A miniature all-fiber micro-force sensor of this type exhibited an ultrahigh force sensitivity of 1.51 nm μN−1, a detection limit of 54.9 nN, and an unambiguous sensor measurement range of ~2.9 mN. The Young’s modulus of polydimethylsiloxane, a butterfly feeler, and human hair were successfully measured with the proposed sensor. To the best of our knowledge, this fiber sensor has the smallest force-detection limit in direct contact mode reported to date, comparable to that of an atomic force microscope (AFM). This approach opens new avenues towards the realization of small-footprint AFMs that could be easily adapted for use in outside specialized laboratories. As such, we believe that this device will be beneficial for high-precision biomedical and material science examination, and the proposed fabrication method provides a new route for the next generation of research on complex fiber-integrated polymer devices.

Researchers demonstrate the replication of 3D natural gyroid nanostructures with superior optical performance and properties.