Work Package 2

Laser digital micro-fabrication processes for sensing applications

This work package will be led by NTUA. WP2 will focus on two laser digital micro-fabrication processes named laser printing and selective laser curing. Most of the WP2 activities will be carried out at the academic partners who have an expertise on the specific field. The incorporation of the academic partners' knowledge into a large scale processing concept will be the objective for the SME partner. The activities are separated in two main subtasks in terms of the applications:

• Laser digital micro-fabrication of 2D conductive interconnects,
• Laser micro-printing of biosensors.

Description of work

Laser digital micro-fabrication of 2D conductive interconnects
Materials selection will take place among commercially available metallic (Au, Ag, Cu) NP inks and pastes. Laser printing of metallic NP inks will be performed using short and ultrashort laser pulses for the fabrication of 2D conductive interconnects. The receiving substrates will be standard microelectronic materials such as silicon, glass, silicon dioxide etc. as well as flexible polymeric substrates, which are widely used for organic electronics. The laser processing conditions will be optimized for printing 2D interconnects with a resolution of at least 10 um. The innovative selective laser curing process will be employed using ultrashort laser pulses in order to achieve a sub-micron resolution. The morphological and electrical characterization of the printed interconnects will be performed at the characterization facilities of the academic partners (SEM, AFM, profilometer, I-V characterization equipment). The academic partners in close collaboration with the SME will define the processing parameters (laser source, ink viscosity properties) for large scale printing of interdigitated interconnects. These types of interconnects, which are known as interdigitated electrodes (IDEs) will serve as sensing substrates for the biosensors fabrication subtask.
Laser micro-printing of biosensors.
The work within the biosensors fabrication subtask will be focused on the direct laser microprinting/immobilization process, which was recently demonstrated by the NTUA group. Environmental biosensors will be developed by direct laser printing of active biomaterials onto the IDE sensors substrates. The optimum processing conditions for direct laser immobilization onto the sensor substrates will be investigated for a wide range of photosynthetic materials including thylakoids, isolated photosynthetic complexes and photosynthetic algae. The biomaterials will be transferred in liquid phase using short laser pulses and the resulting biosensors will be tested for pesticides detection. The NTUA group has recently been equipped with the appropriate electrochemical instrumentation for real time analysis of the biosensors. Laser micro-printing will be also combined with silica gel hydro gel and polymer cross linking encapsulation methods in order to investigate the optimum immobilization method. The resulting biohybrid layers will provide improved life time of the biomaterial activity and enhanced stability of the biosensors performance. Within this interdisciplinary subtask the direct immobilization method is expected to provide a tool for overcoming the drawbacks of the conventional deposition/immobilization methods.

Risk Analysis

The risks of this WP are related first to the laser curing process and the temperature induced on the organic substrates. Actions may be needed in order to achieve an efficient sintering of the metallic inks while preserving the substrates, such as the use of different laser systems, with different pulse durations, to cure the metallic lines as a function of their thickness. Inks with nanoparticles of different sizes will be tested too, because smaller are the particles, lower is the sintering temperature. Another possible risk is the life time of the biosensors and the success of the encapsulation process and the corrective actions will involve different polymer materials.