Chunlei Wang

Abstract

Florida International University (FIU) is pursuing business partners interested in commercializing Electronically Activated C-MEMS Electrodes for On-chip Micro Super-capacitors as a very promising method for fabricating electrochemical micro-capacitors. Carbon micro-electrode arrays for use in micro-capacitors are fabricated using the carbon microelectromechanical system (C-MEMS) technique. This technique employs electrochemical activation in order to improve the capacitive behavior of carbon micro-electrode arrays. Cyclic voltammetry (CV) and galvanostatic charge-discharge results indicated that electrochemical activation effectively increases the capacitance of micro-electrode arrays by as many as three orders of magnitudes. Specific geometric capacitance reaching as high as 7mFcm-2 at a scan rate of 5mVs-1 has been observed with just 30 minutes of electrochemical activation. In addition after 1000 CV cycles the capacitance loss is less than 13 percent. This indicates that electrochemically activated C-MEMS micro-electrode arrays are promising candidates for on chip electrochemical micro-capacitors. FIU inventors have successfully demonstrated that C-MEMS fabricated micro-electrodes are potentially capable of delivering energy storage solutions for micro-devices. In addition fabrication of higher aspect ratio micro-electrodes could increase the device’s surface area while maintaining a desirable in the limited footprint. Other future developments include fabrication of high aspect ratio 3D electrodes, which would increase adhesion of carbon current collectors to the substrate, and optimizing the conditions of electrochemical activation.

Benefit

For the first time C-MEMS electrodes have been successfully activated using electrochemical activationActivated C-MEMS electrodes provide a higher specific capacitance compared to non-activated C-MEMSThree dimensional C-MEMS electrodes provide more efficient surface area compared to conventional thin film electrodesAdditionally, the C-MEMS technique is compatible with other microfabrication techniques

Market Application

Can be used as three dimensional electrodes for on-chip electrochemical micro-supercapacitorsThe technology has specific applications in the fields of micro-power sources and energy storage

Abstract

Scintillators are materials that exhibit luminescence when excited by ionizing radiation– such as X-rays and gamma rays. In other words, high energy rays are changed to visible light. Doped glass scintillators are favored over other scintillators because of their good mechanical, chemical, thermal, and absorbance properties. The issue that arises when considering doped glass scintillators is that the dopants need to be stable in their less stable, luminant, oxidation states. This shortcoming requires manufacturers to use additional reducing agents or reducing environments during the fabrication process. FIU inventors have invented alternative methods of fabricating doped glass scintillators. A stereolithography process is used, which is a three-dimensional printing technique that uses layering, and binding using visible light. Stereolithography allows for the doping to be carried out before the green body composite formation so that homogeneity of the dopant is improved. Vacuum sintering also assists with keeping the dopants in their luminescence-producing oxidation state, decreasing the need for additional reducing agents.

Benefit

· The need for additional reducing agents or reducing environments is reduced significantly · The dopant is stable in its luminescent oxidation state

Market Application

· Use for detection of ionizing radiation · Useful in the electrical power industry as spectral converters for solar cells · Use in medical imaging devices for diagnostics

Abstract

Commercially-available graphene/graphene oxide (GO) materials are mostly produced based on top-down wet chemical and/or electrochemical approaches for (i) exfoliation of GO from graphite sources and (ii) reduction of exfoliated GO into graphene or reduced graphene oxide (rGO). In the wet chemical processes such as Hummers method and modified Hummers method, strong oxidizing agents in a strong acidic medium are typically used for the production of GO, and strong reducing agents are typically used for the formation of rGO. These sets of reactions can introduce relatively high amounts of defects into the rGO sheets and produce toxic chemicals. The majority of commercially-available materials are actually graphite microplates with less than 10% graphene content, and none of the samples have more than 50% graphene content. On the other hand, the electrochemical techniques have been increasingly employed in graphene mass production with the advantages of high production yield of relatively high purity products in simple and cost-effective ways. The electrochemical approaches are typically based on intercalating molecules or charged ions between the graphene layers of a graphite electrode to facilitate the exfoliation and collection of the graphene nanosheets from the solution. Although the anodic approach is more common due to the higher efficiency of intercalation and expansion, the cathodic exfoliation is more desired in order to avoid unwanted chemical functionalization and damage to the graphite basal plane that occur during the anodic exfoliation.The FIU invention uses bipolar electrochemistry (BPE) to provide a single-step and controllable process for simultaneously exfoliating a graphite source and depositing both graphene oxide and reduced graphene oxide layers on conductive substrates. A bipolar electrochemical cell is used for a three-in-one deposition and can include two wired pieces of graphite to monitor the amount of current that passes through the bipolar electrode. Upon the application of the direct current (DC) voltage across the feeding electrodes, several electrochemical processes take place, resulting in a three-in-one in situ exfoliation, reduction, and deposition in a single step and in an environmental friendly manner to directly form functional graphene-based electrodes.

Benefit

· Fabrication of high-quality graphene · Economical, safe, and easy to control · Environmentally friendly compared to existing methods · Assist in mass production of graphene-based devices

Market Application

Energy storage, optical and electronic devices, sensors for biomedical applications.