Victor A. Lifton

Reserve battery architecture based on superhydrophobic nanostructured surfaces

This letter presents the details of a novel battery architecture based on superhydrophobic nanostructured materials. Both electrodes of a battery are formed on nanostructured silicon surfaces that are subsequently treated to make them superhydrophobic, effectively separating the liquid electrolyte from the active electrode materials. When the battery is activated to provide power, a phenomenon called electrowetting promotes electrolyte penetration into the electrode space to initiate an electrochemical reaction. This architecture makes possible an extremely long shelf life, instantaneous ramp-up to full power, and chemistry-independent functionality.

Options for additive rapid prototyping methods (3D printing) in MEMS technology

Purpose – This study aims to investigate the options for additive rapid prototyping methods in microelectromechanical systems (MEMS) technology. Additive rapid prototyping technologies, such as stereolithography (SLA), fused deposition modeling (FDM) and selective laser sintering (SLS), all commonly known as three-dimensional (3D) printing methods, are reviewed and compared with the resolution requirements of the traditional MEMS fabrication methods. Design/methodology/approach – In the 3D print approach, the entire assembly, parts and prototypes are built using various plastic and metal materials directly from the software file input, completely bypassing any additional processing steps. The review highlights their potential place in the overall process flow to reduce the complexity of traditional microfabrication and long processing cycles needed to test multiple prototypes before the final design is set. Findings – Additive manufacturing (AM) is a promising manufacturing technique in micro-device techn...

Optical MEMS devices for telecom systems

As telecom networks increase in complexity there is a need for systems capable of manage numerous optical signals. Many of the channel-manipulation functions can be done more effectively in the optical domain. MEMS devices are especially well suited for this functions since they can offer large number of degrees of freedom in a limited space, thus providing high levels of optical integration. We have designed, fabricated and tested optical MEMS devices at the core of Optical Cross Connects, WDM spectrum equalizers and Optical Add-Drop multiplexors based on different fabrication technologies such as polySi surface micromachining, single crystal SOI and combination of both. We show specific examples of these devices, discussing design trade-offs, fabrication requirements and optical performance in each case.

Robust Si-Based Membranes for Fluid Control in Microbatteries Using Superlyophobic Nanostructures

Mechanically robust superhydrophobic Si-based membranes are described. The membranes are prepared using microelectromechanical-systems-type processing and implement “nanonail” design features that enable superlyophobic (also called omniphobic, superolephobic) behavior. A variety of low- and high-surface-tension liquids are repelled by such porous membranes without liquid penetrating into the pores of the membrane. Electrowetting transitions have been successfully implemented as a way to demonstrate electrically triggered and tunable permeability of the structures. Long-term stability of the hydrophobic coatings based on fluoropolymers has been evaluated using contact angle measurements. Among those, Teflon-based coatings tend to show the best survivability in aqueous and organic electrolytes for periods longer than 200 days of continuous exposure at room temperature and at 60 °C. Such robust membranes are currently used in reserve microbattery technology and microfluidic devices and, potentially, could enable other applications involving fluid separation, fuel cells, and filtration.

Design and Fabrication of Addressable Microfluidic Energy Storage MEMS Device

Design and fabrication of microfluidic energy storage devices that are based on the control of the liquid electrolyte inside a power cell are presented. A 12-cell array of individually addressable reserve microbatteries has been built and tested, yielding ~ 10-mAh capacity per each cell in the array. Lithium and manganese dioxide or carbon monofluoride (Li/MnO2 and Li/CFx) have been used as anode and cathode in the battery with LiClO4 -based electrolyte. Inherent power management capabilities allow for sequential single cell activation based on the external electronic trigger. The design is based on the superlyophobic porous membrane that keeps liquid electrolyte away from the solid electrode materials. When power is needed, battery activation (a single cell or several cells at once) is accomplished via electrowetting trigger that promotes electrolyte permeation through the porous membrane and wetting of the electrode stack, which combines the chemistry together to release stored electrochemical energy. The membrane and associated package elements are prepared using microelectromechanical system fabrication methods that are described in details along with the assembly methods.

Electrostatically actuated membrane mirrors for adaptive optics

We are developing membrane mirrors for use in adaptive optics, particularly in astronomy and vision science. We have micro-fabricated membrane mirrors from single crystal silicon using wet chemical etching and reactive ion etching. Membrane size, tension and operating voltage were selected to allow greater deformation of the mirror surface at low operating voltage than previous membrane mirror designs. Mirror devices consist of independently fabricated membrane and electrode array chips that are flip chip bonded together. We have fabricated electrode arrays with 256 and 1024 electrodes, and active diameters ranging from 6-10 mm (comparable to the size of the human pupil). Membrane-electrode hybrids are mounted to ceramic packages, wire bonded, and driven by off chip, D/A electronics. These devices are milestones in the development of an electret membrane mirror.

Polyimide Spacers for Flip-Chip Optical MEMS

Multichip integration provides an attractive means to overcome space limitations for large-port-count optical microelectromechanical systems (MEMS) routing systems by allowing actuation and control wiring to be fabricated separately on one chip and then attached beneath a second chip that is populated with a densely packed mirror array. In such systems, vertical as well as horizontal chip alignment is critical when a large but very uniform separation must be maintained across the extent of the array. A technique for creating a structure that simultaneously provides accurate large-gap spacing and acts as a chip-bonding agent is presented here. Specialized processing of an 80- mum thick photoimaged polyimide structure for bonding mirror and electrode chips for a 1296-mirror array is described, along with measurements of height uniformity within 1% and structure characterization demonstrating suitability for production and long-term stability. The process parameters and simplicity of the technique make it suitable for a wide range of applications where MEMS must be integrated with electronic control circuitry. [2006-0042].