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In this paper, a procedure to release SU-8 layers from glass substrates using typical undesirable effects is described. The proposed process can be used as lift off or stripping. The releasing method consists in taking advantage of the undesired thermal delamination, and the effect of UV overexposure on the delamination temperature, which are considered undesirable effects. This implies the use of SU-8 for both structural and lift off using the same facilities, without any additional photoresist, material, remover or developer. In this way, the fabrication of a glass/gold microelectrodes array (MEA) for cell culture applications is carried out as a proof of concept. The MEA is composed of gold tracks of 1.5 mm width and 8 electrodes with radii between 25 and 500 μ m at its ends. The SU-8 photoresist is also used as an insulation layer releasing the pads and the electrodes. Finally, biological experiments with neuroblastoma cells SK-N-SH cultured on the MEA surface were carried out in order to validate and demonstrate the biocompatibility of both the MEA and the process. The fabrication and biological results were successful, showing a normal cell proliferation over the developed MEA. [ABSTRACT FROM AUTHOR]

In this paper, a method of integration of silicon sensors in microfluidic platform is presented. In particular, impedimetric silicon sensors are used to make the proof of concept. These sensors are integrated in a FR4 substrate [component of a printed circuit board (PCB)] where the SU-8 microfluidic circuit is built. In order to generalize the application of this method, standard processes that are typical in the laboratories are used. The material to fabricate those microfluidic circuits is the negative photoresist SU-8. The method of fabrication consists on performing the typical SU-8 process over the silicon chips once they are inserted in the FR4 substrate. This method must provide flatness to avoid irregular microchannels. Also, the proposed process must ensure the insulation of the electric connections to avoid short-circuits when the sample fluid flows through the systems, and bondings robust enough to support a spinning step. In addition, the SU-8 process must be clean enough to keep the capability of measurement of the sensors. This cleanness has been studied using different conductivities of a KCl solution, providing good results. Finally, apart from integrating microfluidic and electronics in the same substrate, this method of integration provides an approach to the optimum between low cost, simplicity and precise measurements thank to the use of inexpensive PCB-based platforms and precise silicon sensors. [ABSTRACT FROM AUTHOR]