Biomedical subjects

Philip D Rack

Publications and source records attributed to Philip D Rack.

3 recordsLinked to original sources

PubMed2006

An endothelial cell compatible biosensor fabricated using optically thin indium tin oxide silicon nitride electrodes.

This study describes the fabrication and performance of an endothelial cell compatible, optically thin, indium tin oxide (ITO) microimpedance biosensor. The biosensor was constructed by sputtering a thin insulating layer of silicon nitride (Si(3)N(4)) onto a 100 nm thick ITO layer. Indium tin oxide electrodes were formed by chemically etching 250 or 500 microm diameter holes through the Si(3)N(4) insulating layer. The exposed ITO electrode was electrically connected to an ITO counter electrode, approximately 2 cm(2) in area, via a 400 microL well containing cell culture media. A lock-in amplifier circuit monitored the impedance of porcine pulmonary artery endothelial cells (PPAECs) cultivated on the electrodes as a function of frequency, between 10 and 100 kHz, and as a function of time, at 5.62 kHz. The ITO-Si(3)N(4) microelectrodes provided consistent and repeatable impedance measurements to the attachment and spreading of PPAECs. In addition, the ITO-Si(3)N(4) electrodes were recyclable, robust, resistant to ethanol sterilization, and had a high optical transmittance. Most importantly, the ITO-Si(3)N(4) electrodes allowed optical access for dynamic cellular attachment imaging. The 5.62 kHz time dependent cellular impedance response to the drug Cytochalasin D further demonstrated the feasibility of using this electrode configuration for dynamic cellular impedance studies.

Animals↗

PubMed2006

Reversible electrowetting of vertically aligned superhydrophobic carbon nanofibers.

Reversible electrostatically induced wetting (electrowetting) of vertically aligned superhydrophobic carbon nanofibers has been investigated. Carbon nanofibers on a 5 x 5 microm pitch were grown on Si substrates, electrically insulated with a conformal dielectric, and hydrophobized with fluoropolymer. This nanostructured scaffold exhibited superhydrophobic behavior for saline (theta approximately 160 degrees). Electrowetting induced a contact angle reduction to theta approximately 100 degrees. Competitive two-liquid (dodecane/saline) electrowetting exhibited reversibility on the same nanostructured scaffold. Without applied bias, ultra-fine-point tip (approximately 25 nm radius) nanofibers result in effectively zero capacitance with the overlying saline layer. Complete electrowetting of the substrate is confirmed as capacitance values increase by several orders of magnitude with increased wetting. These results demonstrate the applicability of reversible electrowetting on nanostructured scaffolds and use of nanofabricated structures that can be integrated with various micro- and nanoelectronic technologies.

Electrons↗

PubMedDate not supplied

Pressure effect of growing with electron beam-induced deposition with tungsten hexafluoride and tetraethylorthosilicate precursor.

Electron beam-induced deposition (EBID) provides a simple way to fabricate submicron- or nanometer-scale structures from various elements in a scanning electron microscope (SEM). The growth rate and shape of the deposits are influenced by many factors. We have studied the growth rate and morphology of EBID-deposited nanostructures as a function of the tungsten hexafluoride (WF6) and tetraethylorthosilicate (TEOS) precursor gas pressure and growth time, and we have used Monte Carlo simulations to model the growth of tungsten and silicon oxide to elucidate the mechanisms involved in the EBID growth. The lateral radius of the deposit decreases with increasing pressure because of the enhanced vertical growth rate which limits competing lateral broadening produced by secondary and forward-scattered electrons. The morphology difference between the conical SiO(x) and the cylindrical W nanopillars is related to the difference in interaction volume between the two materials. A key parameter is the residence time of the precursor gas molecules. This is an exponential function of the surface temperature; it changes during nanopillar growth and is a function of the nanopillar material and the beam conditions.

Journal Article↗