Completed Projects

Solid-On-Liquid Technology for Suspended Microchannel Fabrication

The mechanical nature of many fundamental biological processes justifies the development of nanomechanical tools to sense and actuate on biological systems. In order to provide real-time detection, the sensors are usually immersed liquid, which lowers their quality factor and hence deteriorates frequency stability. An elegant solution is the fabrication of hollow structures (suspended micro-channels – SMCs) with the liquid and the analytes flowing inside them instead of around them. SMCs’ fabrication normally requires several photolithographic and etching steps as well as the use of sacrificial materials in order to create the hollow structures. 

In this project, an alternative process is proposed. The solid-on-liquid deposition (SOLID) technology is an innovative fabrication method developed in HES-SO La-Chaux-de-Fonds (Dr. Homsy). In short, a layer of parylene is deposited on top of a liquid, hermetically sealing it and allowing for the definition of hollow and low stress structures. The student will work in collaboration with the Advanced NEMS group and Dr. Homsy in order to apply the SOLID technology to suspended microchannels’ fabrication. Devices will be tested using well known fluids with the purpose of demonstrating the feasibility of SMCs as a real time sensor for evaluating fluid-mechanical properties.

 

 

 

Image: Solid-on-liquid technology (SOLID)

 

 

Image taken from:

J. Charmet et al., Thin solid films 2010

                                    

 Project Components:

  • Study of literature on SMCs and solid-on-liquid technology
  • Design and fabrication of suspended microchannels.
  • Microfluidic Characterization

 

Type of project:

Section(s):

Contact(s):

Master/Semester Project

Microengineering, Bioengineering

Guillermo Villanueva

Implementation of an Optical Interferometer

Laser interferometers, when coupled with sensitive micro-motors, are excellent metrological instruments that can be used in micro- and nanoengineering for measuring small displacements and topography. In this project, the student will assemble a laser interferometer system as well as create a program in LabVIEW or Simulink that will allow the setup to conduct 2D scans of mechanical resonators. Finally, some measurements will be completed on NEMS to test the scanning program.

 

 

Example of an optical interferometer

Image taken from:

Karabalin et al., APL, 2009

 

Project Components:

  • Design interferometer
  • Purchase parts
  • Assemble interferometer system
  • Code 2D scanning program in LabVIEW or Simulink
  • Conduct scanning experiments on cantilevers

 

Type of project:

Section(s):

Contact(s):

Semester project

Microengineering, Physics

Guillermo Villanueva

Suspended Microresonator Fabrication: Atomic Layer Deposition

Atomic Layer Deposition (ALD) is a unique vapor phase chemical process that yields ultra-thin film coatings with exceptional conformality on highly non-uniform and non-planar surfaces, often with sub-nanometer scale control of the coating thickness. For many materials, the ALD reaction chemistry proceeds readily at lower temperatures than chemical vapor deposition (CVD) processes, making ALD attractive, for example, for integration with biological or synthetic polymer structures. Aluminum oxide, also known as alumina, is a well-proven, biocompatible ceramic that has been used as a dental restorative material for many years.

In this project the student will face the challenge of developing a new technology for suspended micro-resonator (SMRs) fabrication, through aluminum oxide atomic layer deposition on photoresist structures.

 

Fig.1 ALD cycle for Aluminum Oxide Fig.2 Schematic of SMR

 

Fig.1 taken from: http://www.che.ncsu.edu/thinfilm/pages/Basics_of_ALD.html

 

Project Components:

  • Fabrication and characterization of aluminum oxide ALD on top of photoresist
  • Fabrication and characterization of suspended aluminum oxide resonators

 

Type of project:

 

Section(s):

Contact(s):

Semester/Master project

Semester project currently in progress

Microengineering, Material Science, Physics

Guillermo Villanueva

Suspended Microresonator Fabrication: Fusion Bonding of Silicon Nitride Interfaces

Suspended micro-resonators are innovative devices where a U-shaped micro-fluidic channel is embedded inside a resonant beam. With these devices, there is a possibility to perform real time analysis of fluidic samples while the overall device is in vacuum, which allows for high resolution mass sensing applications. However, the fabrication process is extremely complicated, thus limiting the actual development of such devices.

We therefore propose a new strategy for SMRs fabrication, where a fusion bonding of two silicon nitride surfaces is performed. This idea drastically reduces the fabrication stages and avoids long wet etching steps which are otherwise necessary for the channel definition.

The student will also be involved in the microfluidic and mechanical characterization of the fabricated structures.

 

Fig.1 Schematic of SMR Fig.2 SEM image of a structured sample cross-section showing the bonding interface near an etched trench

 

Fig.2 taken from: 2011 J. Micromech. Microeng. 21 125015

Project Components:

  • Optimization and characterization of fusion bonding of silicon nitride interfaces
  • Mechanical and microfluidic characterization of suspended micro resonators

 

Type of project:

 

Section(s):

Contact(s):

Master/Semester project

Semester project currently in progress

Microengineering, Material Science, Physics

Guillermo Villanueva

Development of Unique Silicon Nitride Resonators

There is interest in fabricating unique resonators that can be packaged with products. In this project, silicon nitride is used as the resonating material, which is a well-established thin film in micro- and nanotechnology. In collaboration with CNM Barcelona, the surfaces of the silicon nitride resonators are adapted in such a way as to uniquely alter their resonating properties. The student will study the theory behind micro- and nano-resonators and interferometry, characterize structures such as shown in the figures below and fabricate new structures based on the characterization results. There is a possibility of a paper at the end of the project.

 

 
Fig. 1 Silicon nitride resonators fabricated at CMi Fig. 2 Clamped beam with patterned surface

 

Project Components:

  • Study of theory behind micro- and nano-resonators and interferometry
  • Characterization of silicon nitride resonators
  • Fabrication of silicon nitride resonators

 

Type of project:

Section(s):

Contact(s):

Master/Semester project

Microengineering, Material Science, Physics

Guillermo Villanueva

Study of Silicon Nitride Properties – Effects on Resonators

The deposition of silicon nitride is highly dependent on the gas flow ratio and temperature conditions. Although some study of the properties of silicon nitride’s material properties has been made in the past, an extensive study of silicon nitride with different deposition conditions has yet to been conducted. In this project, several depositions of silicon nitride films will be made and measurements of (1) stoichiometry, (2) refractive index, and (3) internal stress will be performed. Then, resonators will be fabricated using the deposited layers of silicon nitride and the quality factor of said resonators will be measured so that internal losses can be characterized. There is a possibility of a paper based on the results of the project.

 

Example of silicon nitride resonators Measurement of the quality factor

 

Images taken from: 

Schmid et al., PRB, 2011

 

Project Components:

  • Fabrication and characterization of silicon nitride films
  • Fabrication and characterization of silicon nitride resonators

 

Type of project:

Section(s):

Contact(s):

Master/Semester project

Microengineering, Material Science, Physics

Guillermo Villanueva

Design and Fabrication of Passive Microphones

Design

Master Project

You will do Design, Modelling and Fabrication

We want to make microphones without batteries

Click for more details

PZE Suspended Micro-channel resonators

PZE Suspended Micro-channel resonators

SEM image of two free-clamped hollow cantilevers

Master Project

You will do Characterization

We want to rule microfluidics with the fabricated devices

Click for more details