## 1 Introduction  
Over the past few decades, an array of compound refractive lenses (CRLs [1; 2; 3]) for hard X-rays, also known as a Shack-Hartmann sensor (SHS), has been applied for wavefront analysis and multi-contrast imaging of weakly absorbing and porous objects with significantly reduced single exposure time due to the focusing properties of CRLs [4; 5]. When a monochromatic X-ray plane wave illuminates a CRL array, an array of point foci is generated. A weakly absorbing object placed in front of or just behind the SHS leads to a displacement of the foci in the detector plane, allowing for reconstructing of a phase-contrast image. In the case of a porous object, the foci broaden, indicating scattering effects and resulting in a dark-field contrast image. Each contrast (absorption, phase, and scattering) can be reconstructed via Fourier transform or two-dimensional (2D) Gaussian fitting [6; 7]. That method provides high temporal resolution and high sensitivity. Using an array of CRLs, the local X-ray flux density is increased at the focal distance. Accordingly, the so-called single-shot X-ray multi-contrast imaging based on an array of CRLs, in combination with high frame-rate detectors, provides microsecond temporal resolution and allows for the investigation of dynamic processes [8]. However, the spatial resolution of this technique is equal to the distance between neighboring point foci and, consequently, to the period of the 2D array (tens of microns) [6]. The spatial resolution could be enhanced by scanning the object through a large number of point foci in combination with the super-resolution reconstruction, as was demonstrated using the 1D-line array of line focus CRLs [9]. Nevertheless, by utilizing the 1D array of CRLs, the spatial resolution is increased only in the scanning direction and limited by the X-ray line focus size (full width half maximum, FWHM). Thus, in the direction perpendicular to the scan direction it is equal to the size of a low resolution detector pixel. Consequently, the development of a 2D array of CRLs generating the point foci in the (sub-) \(\upmu\)m range will overcome the mentioned limitations and increase the spatial resolution in both directions. Recently, the use of 2D refractive lens arrays, fabricated either by additive manufacturing of a polymer with low radiation stability or by an embossing process of polyimide foils using a needle with paraboloid tip, were demonstrated for energies below 15 keV and for a field of view (FoV) of 1 mm\({}^{2}\) and 6.5 \(\times\) 6.5 mm\({}^{2}\), which limits the scope of the samples studied [10,11]. Fabrication of 2D CRLs for higher energies by these techniques is a challenging task at the moment. Moreover, the current 2D refractive lenses include stitching/shifting errors, influencing the focusing performance (the point foci size is in the range of ten microns). The use of higher photon energies would allow for the study of optically thick objects, which are of high interest for the material sciences, for example, for characterization of cracks distribution in metallic plates and composite materials. Therefore, the target of this work was the development of X-ray CRL arrays for higher energies (from 15 keV to 100 keV), generating smaller point foci, allowing for a spatial resolution in the (sub-) \(\upmu\)m range with a large area (\(>\)1 mm\({}^{2}\)) to study relatively big samples. We present a 2D 34 \(\times\) 34 multi-lens array for sub-pixel resolution scanning transmission hard X-ray imaging (see Figure 1). This array has biconcave parabolic refracting surfaces, offers 1156 foci in a 3.5 mm\({}^{2}\) large field of view, and is made out of a radiation stable polymer. The required detector only needs large 55 \(\upmu\)m \(\times\) 55 \(\upmu\)m pixels. Scanning the sample with steps clearly below the detector's pixel size and slightly below the focal spot size of the individual lenslets provides a resolution in the range of the focal spot size over the entire field of view.