B. Arda Gozen

High-density soft-matter electronics with micron-scale line width.

A method to produce soft and stretchable microelectronics composed of a liquid-phase Gallium-Indium alloy with micron-scale circuit features is introduced. Microchannels are molded onto the surface of a poly(dimethylsiloxane) (PDMS) elastomer and filled with EGaIn using a micro-transfer deposition step that exploits the unique wetting properties of EGaIn in air. The liquid-filled channels function as stretchable circuit wires or capacitor electrodes with a 2 μm linewidth and 1 μm spacing.

Modeling and experimentation of bone drilling forces

Prediction and control of bone drilling forces are critical to the success of many orthopaedic operations. Uncontrolled and large forces can cause drill-bit breakage, drill breakthrough, excessive heat generation, and mechanical damage to the bone. This paper presents a mechanistic model for prediction of thrust forces and torques experienced during bone drilling. The model incorporates the radially varying drill-bit geometry and cutting conditions analytically, while capturing the material and friction properties empirically through a specific energy formulation. The forces from the chisel edge are modeled by considering the indentation process that occurs in the vicinity of the drill-bit axis. A procedure is outlined to calibrate the specific energies, where only a small number of calibration experiments are required for a wide range of drilling conditions and drill-bit geometry. The calibration parameters for the cortical portions of bovine tibia are identified through drilling tests. Subsequently, a series of validation tests are conducted under different feed rates and spindle speeds. The thrust forces and torques were observed to vary considerably between bones from different animals. The forces from the model were seen to match well with those from the experimentation within the inherent variations from the bone characteristics. The model can be used to select favorable drilling conditions, to assist in robotic surgeries, and to design optimal orthopaedic drill bits.

A Rotating-Tip-Based Mechanical Nano-Manufacturing Process: Nanomilling

We present a rotating-tip-based mechanical nanomanufacturing technique, referred to here as nanomilling. An atomic force microscopy (AFM) probe tip that is rotated at high speeds by out-of-phase motions of the axes of a three-axis piezoelectric actuator is used as the nanotool. By circumventing the high-compliance AFM beam and directly attaching the tip onto the piezoelectric actuator, a high-stiffness arrangement is realized. The feeding motions and depth prescription are provided by a nano-positioning stage. It is shown that nanomilling is capable of removing the material in the form of long curled chips, indicating shearing as the dominant material removal mechanism. Feature-size and shape control capabilities of the method are demonstrated.