## 1 Introduction  
Biomolecular probes such as antibodies, aptamers, oligonucleotides, and proteins are one of the fundamental components of biosensors. Surface immobilized biomolecular probes provide the critical interface between the solid surface and the liquid environment containing target molecules [1]. One method to pattern the probes on solid surfaces is polydimethylsiloxane (PDMS) based micro-contact printing [2]. Micro-contact printing is used to immobilize various biomolecules such as lipid-bilayers [3], immunoglobulins G [4], laminin [5], and DNA [6] on solid surfaces. Using the high affinity and specificity of the biotin-streptavidin interaction streptavidin and biotin conjugated bovine serum albumin (BBSA) are micro-contact printed on gold surfaces as probe molecules creating binding sites for other biotin or streptavidin conjugated biomolecules [7; 8].  
One of the patterns preferred in micro-contact printing methods is barcode-like, alternating linear lines. The printed lines are for sensing and the spacing between printed lines can be used for control, the alternating pattern enables diffraction measurements [8; 9]. Different methods such as atomic force microscopy (AFM) [4], fluorescence microscopy [3], and X-ray photoelectron spectroscopy (XPS) [10] are used to quantify the binding of biomolecules on micro-contact printed lines. These methods are costly and they require bench top equipment and experts.  
Micro/nano immunomagnetic beads enable target capture and separation in biosensing applications and due to these important features they are also employed on micro-contact printed lines to transfer target molecules to the sensor surface, and to form sandwich assays and reflective surfaces for laser diffraction measurements [7; 9].  
Cell phone microscopy is gaining in popularity due to being low cost, and the wide-spread use of cell phones [11]. Lens attachments [12; 13] or lens free computational [14] strategies were developed to turn cell phones into optical microscopes. One approach is to attach a spherical ball lens to a cell phone camera to provides magnification and record microscopic images [15; 16]. Spherical ball lenses are low cost and easy to assemble. In our previous research we showed that a low cost spherical lens provide 3-5 micron resolution but noise is an important demerit; the images acquired by a cell phone microscope have a low contrast to noise ratio (in press, [17]). We also showed that images recorded with a cell phone can be analyzed using Matlab image processing codes running on cloud servers [18].  
In this paper we use image-processing methods to enhance the images of immunomagnetic beads on micro-contact printed patterns recorded by a cell phone microscopy (Figure 1). The cell phone microscopy is composed of a Samsung Note S4 cell phone, a borosilicate glass spherical ball lens and a polymethylmethacrylate (PMMA) lens holder (Figure 2). The image enhancements show that simple cell phone microscopy can be an alternative read-out method to investigate the immunomagnetic beads on micro-contact printed lines. The image processing methods can help to overcome the limitations of the simple spherical ball lens.