Christopher N. Delametter

The effect of interface shape on thermal stress during Czochralski crystal growth

Abstract Numerical techniques are used to calculate the effect on thermal stresses of the shape of the solid-liquid interface during Czochralski crytal growth. The interface is modelled as parabolic and characterized by the magnitude of the maximum deviation from planarity. The temperature field is modelled by neglecting convection and it is characterized by the Biot number H based on the crystals radius. Emphasis is placed on the equivalent shear stress and on the hydrostatic tension near the center of the crystal and near the outer peripheny. The variation of maximum stresses with deviation from planarity is established. The applicability of thermoelastic solutions close to the solid-liquid interface is examined, and the necessity is discussed of directly coupling the constitutive law describing high temperature inelastic deformation to the stress calculation.

A new method for deflecting liquid microjets

A new method is reported for deflecting a microscopic jet emanating from a nozzle away from the nozzle’s axis of symmetry. It relies on putting energy into the jet through an asymmetric heater embedded in the nozzle. This novel phenomenon is probed theoretically. It is shown that jet deflection is set by the competition among three effects. Two of these can be attributed to the variation with temperature of surface tension and the third to that of viscosity. Whether the contact line is fixed or free is shown to profoundly impact the extent of jet deflection at a given flow rate.

Micro-jet nozzle array for precise droplet metering and steering having increased droplet deflection

We present the architecture and fabrication method of a fluidic device with increased droplet deflection. The device is capable of producing picoliter size droplets precisely and steering them. The precision is a consequence of the reproducibility of the nozzles that are made using VLSI technology and tools. In addition, the droplet size is determined by the precise timing of applied heat pulses. We present both experimental and modeling results.