A New Generation of Implantable Drug Delivery Devices Based on the Novel Ultrananocrystalline Diamond (UNCD) Film Technology

M. ZALAZAR; P. GURMAN; O. AUCIELLO; F. GUARNIERI

Conferencia; New Diamond and Nano Carbons Conference; 2012

Ultrananocrystalline Diamond (UNCD) is a promising material for biomedical applications due to its extraordinary mulifunctionality, including tunable electrical conductivity up to the semimetallic level, extremely low wear, very low coefficient of friction, high smoothness, bio-inertness and biocompatibility. UNCD is particularly relevant for implantable medical devices where biological performance of materials must meet very stringent requirements. Drug delivery systems represent an important area in medical devices due to the improvement achieved in drug transport and bio-distribution. The aim of the present work was to design, fabricate and characterize UNCD membranes suitable for passive and active drug delivery devices. A common feature of the passive and active drug delivery devices based on UNCD membranes is the fabrication of the latter. UNCD membranes were fabricated in a clean room facility using thin film deposition and microfabrication techniques, including: 1) UNCD thin film growth by microwave plasma chemical vapor deposition (MPCVD) on a Si substrate, 2) photolithography using a specially designed mask to define the UNCD membrane area, 3) reactive ion etching (RIE) to pattern the membranes and 4) wet chemical etching to create the cavity sustaining the UNCD membrane. Square membranes of 200-1000 /-Lm in size with a thickness ranging between 100-500 nm were fabricated and characterized by Raman spectroscopy, optical microscopy, scanning electron microscopy (SEM) and reflectometry. Fabrication of passive drug delivery devices was done using the focused ion beam (FIB) technique to produce holes with micron to nanoscale dimensions in the UNCD membranes to enable controlled passive drug delivery through the latter. For the active drug delivery device, based on a piezoelectrically actuated valve, a Pt/piezoelectric AIN/Pt layer heterostructure is grown on the UNCD membrane with a Ti adhesion layer, followed by FIB etching to define the valve aperture. The valve can be actively opened and closed by applying voltages between the top and bottom Pt electrodes layers to induce the piezoelectric effect on the AIN layer, thus actuation. Work in progress will be described, showing the optimization of AIN film growth and integration with UNCD membranes and development of fabrication processes to produce piezoelectrically actuated valves. PDMS was used to seal the bottom face of the Si substrate, where the integrated UNCD membrane/cavity structure was fabricated, to create the reservoirs. Work in progress to optimize and test active and passive drug delivery devices based on UNCD membranes will be discussed in the presentation.