Micro/Nano Scale

Temperature limits the sensitivity and resolution of every surface electrical potential measurement made by an AFM today. With existing AFM probes, temperature and current cannot be modulated, thus it is difficult to control temperature or to measure electrical potential at the tip. This device uses an integrated resistive heating element and temperature controls to combine temperature applications with voltage measurements to remove the uncertainty of temperature in surface electrical potential measurements.

Using an integrated resistive heating element, the device has the ability to reach 1000 C and can control the temperature of the AFM probe tip to measure the tip's electrical resistance. This device makes nanoscale surface electrical potential measurements that may be a function of temperature. As this technique modulates the temperature precisely, it removes the temperature uncertainty of surface electrical potential measurements. Using multiple probes on a single chip, the device also addresses the slow-throughput of Dip Pen Nanolithography

Applications:

Semiconductor and surface science as well as repair applications in photo-mask and flat panel displays.

Benefits:

The ability to calibrate and control AFM tip temperature within 1C at temperatures greater than 1000 C. Multiple AFM probes that can be manufactured in bulk and can be addressed individually.

A device that incorporates teachings of the present disclosure may include, for example, a memory array having a first array of nanotubes, a second array of nanotubes, and a resistive change material located between the first and second array of nanotubes. Other embodiments are disclosed.

Conductivity of a liquid solution provides valuable information about the solution, but commercially available conductivity probes are costly and have diameters greater than 1cm, limiting their potential applications. Microscale thin-film liquid conductivity sensors are a novel application of semiconductor processing methodology and are capable of measuring ion concentrations in nanoliter size samples of liquid. The devices can be readily commercialized for small volume sample analysis or for in-vivo measurement in chemical or biological processes and mesoscale machines. Sensors can be fabricated as part of an integrated circuit and may be integrated with other sensors for multiparameter measurements. These robust, low-cost sensors also have potential for a wide range of commercial and industrial monitoring and control applications.

Current, commercially available liquid conductivity sensors are bulky, expensive and unable to measure small sample volumes or to be used for in-vivo and in-situ applications. A newly developed surface and bulk micromachining technique enables the fabrication of low cost, robust sensor probes with temperature compensation and improved packaging on silicon wafers.

From 200 to 2000 devices (depending on desired size) can be fabricated on a 4" silicon wafer, greatly reducing fabrication cost. Pt-black electroplating reduces the electrode/solution interfacial impedance, maintaining measurement accuracy while significantly reducing operation frequency. Reduction of operation frequency eliminates dependence on expensive measurement electronics.

With the new process and 4-electrode measurement, sensor probes can be fabricated with tip widths much less than 100 microns. To improve device accuracy, an RTD temperature sensor can be integrated on the sensor probe tip to provide local temperature compensation. The bulk micromachining method also allows the thermal mass of the sensor to be reduced, thus improving the response time of the probe.

Applications

• Analysis of chemical and biological fluids.
• In-vivo and in-situ measurements for medical testing.
• Controls for washing machine and dishwasher rinse cycles.
• Monitors to improve the performance and safety of water and ice dispensers and water purifiers.
• Devices for monitoring ultrapure water and measuring seawater salinity.

Benefits

• Sensors can measure electrical conductivity in nanoliter size samples over a wide range of solution conductivity.
• The sensor tip accommodates an integrated temperature sensor that enhances sensor accuracy by measuring local temperature.
• A four-electrode design provides independent measurement of current and voltage.
• The device is hundreds of times smaller than commercially available conductivity probes; future devices may be miniaturized to 100 micron tip width.
• Sensors can be operated at very low current and power consumption and are ideal for low-power or battery-operated applications.
• Sensors can be driven at relatively high electric currents, with the resulting high temperature acting to de-foul the electrodes.
• Because of low fabrications costs, sensors can be disposable.

This technology describes a fabrication method for multi-channel, multi-layered microfluidic devices, with numerous functional characteristics capable of integration into a lab-on-a-chip platform. The chip allows broader analytical capabilities in point-of-use microfluidic technology than previously possible, and it does so with exceeding strength and stability.

Fabrication of this chip is made possible by a transfer process of labile membranes and the development of a contact printing method for a thermally curable epoxy-based adhesive. This adhesive has bond strengths that prevent leakage, channel rupture and delamination to nearly 6atm. Channels on the chip - 100 m wide and 20 m deep - are contact printed without the adhesive entering the microchannel.

The chip is characterized in terms of resistivity measurements along the microfluidic channels, electroosmotic flow (EOF) measurements at differing pH levels and laser-induced-fluorescence (LIF) detection of green-fluorescent (GFP) plugs injected across the nanocapillary membrane and into a microfluidic channel. The resulting product is a mixed-polymer micro-nanofluidic multilayer chip, which has the electrical characteristics necessary for use in microanalytical systems.

Applications:

• Solution sample clean-up and preparation: Prepare materials for research faster than ever before.
• Automated lab-on-a-chip: Develop high-throughput, fully-automated systems for life sciences research and drug discovery investigation.
• Laboratory-tests-on-a-card or "Lab Cards": Analyze blood and tissue samples on the spot with portable and hand-held devices.

Benefits:

• Built-in NCAMs: The NCAM (nanocapillary-array membranes) acts as an electrostatic "gateway," permitting only compounds of a particular size and charge to pass through. Integration of NCAMs into microfluidic devices increases the chips' sophistication and analytical capabilities by permitting simultaneous sample streams, multiple molecular manipulations, and controlled reactions and optical verification.
• Vertical nanocapillary interconnects: Sandwiching the NCAMs between layers of nanocapillary interconnects increases both scalability and complexity by allowing unique operations such as the separation of analytes based upon molecular size, channel isolation, enhanced mixing, and sample concentration.
• Optically transparent: Inspect fluids within the channels in the near UV and visible light spectrum.
• Incorporate numerous layers: With large arrays of NCAMS and nanocapillary interconnects, the fabrication method enables a wide degree of functional complexity because each layer can be optimized to a particular task.
• Reliable structure: Strong bonding during fabrication produces a high-test chip, whose nanocapillary arrays maintain stability up to nearly 6atm of pressure, even when several arrays are stacked together.

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