We report a novel method for direct printing of viscous polymers based on a pyro-electrohydrodynamic repulsion system capable of overcoming limitations on the material type, geometry and thickness of the receiving substrate. In fact, the results demonstrate that high viscosity polymers can be easily manipulated for optical functionalizing of lab-on-a-chip devices through demonstration of direct printing of polymer microlenses onto microfluidic chips and optical fibre terminations. The present system has great potential for applications from biomolecules to nano-electronics. Moreover, in order to prove the effectiveness of the system, the optical performance of such microlenses has been characterized by testing their imaging capabilities when the fibroblast cells were allowed to flow inside the microfluidic channel, showing one of their possible applications on-board a LoC platform.

In this study, we report a direct writing method for the fabrication of microfluidic footpaths by pyro-electrohydrodynamic (EHD) jet printing. Here, we propose the use of a nozzle-free three-dimensional printing technique for the fabrication of printed structures that can be embedded in a variety of soft, transparent, flexible, and biocompatible polymers and thus easily integrated into lab-on-chip devices. We prove the advantage of the high resolution and flexibility of pyro-EHD printing for the realization of microfluidic channels well below the standard limit in dimension of conventional ink-jet printing technique and simply adaptable to the end-user desires in terms of geometry and materials. Starting from the description of the innovative approach proposed for the channel fabrication, we demonstrate the design, fabrication, and proof of a microfluidic matrix of interconnected channels. The method described here could be a breakthrough technology for the fabrication of in situ implantable, stretchable, and biocompatible devices, opening new routes in the field of biomedical engineering and wearable electronics.

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A challenging request in the fabrication of microfluidics and biomedical microsystems is a flexible ink-jet printing for breaking the rigidity of classical lithography. A pyroelectric-EHD system is presented. The system has proved challenging spatial resolution down to nanoscale, printing of high ordered patterns, capability of dispensing bio-ink as DNA and protein array for biosensing fabrication, single cells printing and direct printing of nanoparticles. With the method proposed high viscous polymers could be easily printed at high resolution in 2D or in 3D configuration. The pyro-EHD process has been proved for the fabrication of biodegradable microneedles for trasndermal drug delivery and 3D optical waveguides.

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