P. Van Gerwen

Nanoscaled interdigitated electrode arrays for biochemical sensors

Nanoscaled interdigitated electrode arrays were made with Deep U.V. lithography. Electrode widths and spacings from 500 nm down to 250 nm were achieved on large active areas (0.5 mm/spl times/1 mm). These electrodes allow for the detection of affinity binding of biomolecular structures (e.g. antigens, DNA) by impedimetric measurements. Such a sensor is developed, theoretically analyzed, experimentally characterized, and is demonstrated as an affinity biosensor.

Thin-film boron-doped polycrystalline silicon70%-germanium30% for thermopiles

Abstract CMOS-compatible thermopiles can be made by using the available polysilicon layer and aluminium layer as a thermocouple. SiGe would, however, offer a better performance than silicon, mostly due to its much lower thermal conductivity, while it maintains CMOS compatibility. The figure of merit of a highly boron doped (about 10 20 atoms cm −3 ) thin-film poly-Si 70% Ge 30% layer deposited by ultra-low-pressure chemical vapour deposition (ULPCVD) is reported. The figure of merit is measured with a dedicated structure: the Seebeck coefficient is ± 75 μ V K −1 , the thermal conductivity is ± 4.8 W mK −1 and the electrical resistivity is 23 μΩ m. The figure of merit is then calculated to be z ≈ 50 × 10 −6 K −1 .

Thermomechanical characteristics of a thermal switch

Abstract An active radiator tile (ART) thermal valve has been fabricated using silicon micromachining. Intended for orbital satellite heat-control applications, the operational principle of the ART is to control heat flow between two thermally isolated surfaces by bringing the surfaces into intimate mechanical contact using electrostatic actuation. Prototype devices have been tested in vacuum. In the OFF state, the switch provides a very good thermal insulation, whilst with actuation voltages as low as 40 V, it switches to the ON state and a large increase in radiative heat flow can be noticed.

Characterization of Nanoscaled Interdigitated Palladium Electrodes of Various Dimensions in KCl Solutions

Nanoscaled interdigitated electrodes (IDEs) were developed for the purpose of being used as miniature and sensitive affinity biosensors. IDEs with palladium as the electrode material on a SiO2 substrate were made with electrode widths and spacings ranging from 550u2005nm down to 250u2005nm. These sensors were theoretically modeled, enabling the prediction of their impedimetric response in KCl solutions. The strength of the theoretical model was proven by a characterization of IDEs of various dimensions in KCl solutions of different concentrations. The results demonstrate a quite reproducible behavior and a correlation between the impedimetric response in KCl solutions and the electrode dimensions.

Cost effective realization of nanoscaled interdigitated electrodes

Nanoscaled interdigitated electrodes (IDEs) are being developed for the realization of miniaturized and highly-sensitive affinity biosensors. Until now, nanoscaled IDEs have been realized on silicon wafers using deep UV lithography or e-beam patterning. However, for many applications in the biochemical field there is a strong need for cheap and/or disposable sensor devices. Therefore, a new, cost effective fabrication method for nanoscaled IDEs, which can also be applied on cheap, micro-moulded plastic substrates, has been developed. The method is based on the directionality of a vacuum evaporation process and omits expensive lithography steps completely. The feasibility of this electrode deposition technique has been proven by realizing IDEs on silicon substrates. Future work is focused on the realization of IDEs on injection moulded plastic substrates.

ART - A NOVEL THERMAL VALVE FOR TEMPERATURE CONTROL APPLICATIONS

A novel device for controlling the radiative transfer of heat is proposed. An Active Radiator tile (ART) is composed of two parallel plates separated by small thermally insulating posts. In the rest state, the ART presents a large thermal resistance. Application of a suitable potential across the plates causes one plate to deflect into direct contact with other plate, allowing a large conductive heat flow. Thus the ART device acts as a thermal valve. We report the modelling of the mechanical and thermal properties of the device, and progress towards the construction of a laboratory prototype.

CMOS-based sensors and actuators

In many applications, up to millions of sensors or actuators have to be connected to the outside world, making the monolithic integration of circuits mandatory. Monolithic integration is also pursued for mass-produced transducers. Today, monolithic devices include visible and IR imagers, displays, inkjet heads, biochemical and physical sensors. Monolithic integration of transducer-specific processes (such as micromachining) with standard CMOS processes is possible, albeit at an increase of process complexity.

A multi-axial strain gage with octagonal shape

An integrated silicon strain gage for multi-axial measurements is proposed. The device contains 4 x 4 p-type strain gages oriented along orthogonal directions. For reasons of compactness, a particular geometry was developed. The strain gages are located on thinned silicon beams, which are suspended in a support with an octagonal shape. This shape was achieved by micromachining structures along (110) edges as well as along (100) edges.