A New Learning Factory Experience Exploiting LEGO For Teaching Manufacturing Systems Integration

Involving and stimulating students through intensive work in computer laboratories and simulation projects might be a challenging task, often due to the lack of the real manufacturing system that must be modeled and improved. Indeed, studying a manufacturing system that cannot be observed represents a real obstacle for student effective learning. In this paper, we describe the "LEGO FACTORY" initiative, an extra-curricular experience within the Master Degree Study Program in Mechanical Engineering of Politecnico di Milano. The initiative is open to students from any study course of the university. The goal is to exploit learning-by-playing principles to offer scholars the possibility to understand the most common issues in the design and management of manufacturing systems, with a focus on system integration. A miniaturized production system made with LEGO® MINDSTORMS® is provided to students who are asked to accomplish a project aiming at the improvement of the system performances. The participants work in teams and must introduce design modifications and develop technical solutions to address the requirements. The experience is described with the hope that the approach can be replicated in other environments

The use of silicon-germanium superlattices for thermoelectric devices and microfabricated generators

Low dimensional structures such as superlattices have the potential to improve the thermoelectric properties of materials by engineering the scattering of phonons to reduce the thermal conductivity and therefore improve the thermeoelectric performance. Here we demonstrate the reduction in thermal conductivity in Ge/SiGe superlattices using multiple barrier engineering to scatter acoustic phonons at the key wavelengths for thermal transport. The approach allows ZT to be increased in wide quantum well superlattices through the reduction of heterointerfaces which scatter both electrons and phonons

Benchmarking the Use of Heavily-Doped Ge Against Noble Metals for Plasmonics and Sensing in the Mid-Infrared

Despite the recent introduction of heavily-doped semiconductors for mid-infrared plasmonics, it still remains an open point whether such materials can compete with noble metals. We employ a whole set of figures of merit to thoroughly assess the use of heavily-doped Ge on Si as a mid-infrared plasmonic material and benchmark it against standard noble metals such as Au. In doing this, we design and model high-performance, CMOS compatible mid-infrared plasmonic sensors based on experimental material data reaching plasma frequencies up to about 1950 cm−1. We demonstrate that plasmonic Ge sensors can provide signal enhancements for vibrational spectroscopy above 3 orders of magnitude, thus representing a viable alternative to noble metals

A Cardinality-constrained Approach for Robust Machine Loading Problems

The Machine Loading Problem (MLP) refers to the allocation of operative tasks and tools to machines for the production of parts. Since the uncertainty of processing times might affect the quality of the solution, this paper proposes a robust formulation of an MLP, based on the cardinality-constrained approach, to evaluate the optimal solution in the presence of a given number of fluctuations of the actual processing time with respect to the nominal one. The applicability of the model in the practice has been tested on a case study

Integrated Germanium-on-silicon Waveguides for Mid-infrared Photonic Sensing Chips

Germanium-on-silicon waveguides are designed, fabricated and characterized with a novel near-field infrared spectroscopy technique that allows on-chip investigation of the in-coupling efficiency. On-chip propagation along bends and straight sections up to 0.8 mm is demonstrated around λ = 6 μm

Mid-infrared n-Ge on Si Plasmonic Based Microbolometer Sensors

The detection and amplification of molecular absorption lines from a chemical weapons simulant is demonstrated using plasmonic antennas fabricated from n-Ge epitaxially grown on Si. A free-standing Si0.25Ge0.75 microbolometer detector with n-Ge plasmonic antenna is demonstrated as an integrated mid-infrared plasmonic sensor

Mid-Infrared Plasmonic Platform based on Heavily Doped Epitaxial Ge-on-Si: Retrieving the Optical Constants of Thin Ge Epilayers

The n-type Ge-on-Si epitaxial material platform enables a novel paradigm for plasmonics in the mid-infrared, prompting the future development of lab-on-a-chip and subwavelength vibrational spectroscopic sensors. In order to exploit this material, through proper electrodynamic design, it is mandatory to retrieve the dielectric constants of the thin Ge epilayers with high precision due to the difference from bulk Ge crystals. Here we discuss the procedure we have employed to extract the real and imaginary part of the dielectric constants from normal incidence reflectance measurements, by combining the standard multilayer fitting procedure based on the Drude model with Kramers-Kronig transformations of absolute reflectance data in the zero-transmission range of the thin film.Comment: Infrared, Millimeter, and Terahertz waves (IRMMW-THz), 2014 39th International Conference o

n-Ge on Si for Mid-Infrared Plasmonic Sensors

The detection and amplification of molecular absorption lines from a mustard gas simulant is demonstrated using plasmonic antennas fabricated from n-Ge epitaxially grown on Si. Approaches to integrated sensors will be presented along with a review of n-Ge compared to other mid-infrared plasmonic materials

Germanium-on-silicon Waveguides for Mid-infrared Photonic Sensing Chips

Germanium-on-silicon rib waveguides are modelled, fabricated and characterized with a novel near-field infrared spectroscopy technique that allows on-chip investigation of the waveguide losses at 5.8 μm wavelength