We have developed a silicon based miccroelectrode for simultaneous recording of cellular electrical activity and local drug delivery Fabrication scheme relies on the smart combination of Buried Channel Technology and Etching-Before-Grinding. Our micromachining concept provides injection, sampling and electrical recording — all integrated monolithically in a long and subsequently thinned silicon microelectrode. Feasibility of our microelectrode configuration has been demostrated in in vivo experiments using either external pressure (Pongrácz et al) or iontophoretic injection (Fekete et al). 

More details in the following publications:

Z. Fekete. E. Pálfi, G. Márton, M. Handbauer, Zs. Bérces, I. Ulbert, A. Pongrácz, L. Négyessy, Combined in vivo recording of neural signals and iontophoretic injection of pathway tracers using a hollow silicon microelectrode, Sensors & Actuators B-Chemical 236 (2016), 815-824

Z. Fekete, Technology of ultralong deep brain fluidic microelectrodes combined with etching-before-grinding, Microsystem Technologies 21 (2015) 341-344

A. Pongrácz, Z. Fekete, G. Márton, Zs. Bérces, I. Ulbert, P. Fürjes, Deep-brain silicon multielectrodes for simultaneous in vivo neural recording and drug delivery, Sensors and Actuators B: Chemical 189 (2013) 97–105

Z. Fekete, A. Pongrácz, P. Fürjes, G. Battistig, Improved process flow for buried channel fabrication in silicon, Microsystem Technologies 18 (2012) 353-358