De Boer group: Mechanics of Materials

Our group works within the discipline of Mechanics of Materials, which combines a rigorous understanding of the stress states imposed by applied forces with research into the microscopic mechanisms that metals, ceramics and polymers employ to accommodate the associated deformations.

Our current areas of emphasis are in

• Understanding the behavior of grain boundary phases, known as complexions, in metals
• Manufacturing and joining of Inconels, stainless steels, low carbon steels, and refractory metals by the 3-D printing method known as directed energy deposition
• Micro- and nanoswitch reliability, and
• Developing high temperature structural material for applications in microelectromechanical systems and as an actuator material for thin film mechanical behavior studies including creep.

The image to the right shows a test platform our group developed to elucidate the laws of friction at the microscale, as featured in a December 2022 article in the Materials Research Society Bulletin.  We have conducted extensive research on enhancing the reliability of micromachined devices, including fabrication, test and analysis of new structures, and of building advanced test chambers.

We collaborate with faculty in the Materials Science, Electrical Engineering, and Mechanical Engineering departments.

Faculty

Maarten P. de Boer

Professor of Mechanical Engineering

Courtesy Appointment, Materials Science and Engineering

Maarten de Boer earned the bachelor’s degree from Cornell University, and the master’s degree from the University of Colorado, Boulder, both in Electrical Engineering, with an emphasis on solid-state device technology. He earned the PhD from the University of Minnesota in Materials Science, concentrating on fracture mechanics. Before joining Carnegie Mellon in 2007, he fabricated integrated circuits as a process engineer at Hewlett-Packard in Fort Collins, Colorado, and investigated mechanisms underpinning MEMS reliability as a principal member of technical staff at Sandia National Labs, Albuquerque, New Mexico.

Office

Scaife Hall 417

Phone

412-268-8752

Fax

412-268-3348

Email

mpdebo@andrew.cmu.edu

Google Scholar

Maarten P. de Boer

Projects

Self-actuating thin film metals test platforms

The thermal actuator (TA) is a common but powerful actuator in MEMS, typically fabricated using micromachined polycrystalline silicon. We are exploring TAs constructed out of tantalum, a refractory metal [Ni, Pocratsky & de Boer, Nature Micro/Nano, 2021]. It self-actuates upon heating, can withstand high temperature, and its processing is compatible with post-CMOS MEMS. It can also be integrated with a wide variety of metals to exert stress in reliability studies [Ni & de Boer, JMEMS, 2022].

Actuators

The nanotractor actuator takes 50 nanometer steps over a +/- 100 micron range and can pull a load up to 1 milliNewton. It is versatile, serving both as a long range linear actuator and as a high fidelity test instrument. It has been used to study microscale friction and to measure the strength of nanofibers. In recent work, we used the nanotractor to map out stick-slip phase diagrams [Shroff & de Boer, 2014 and 2016], and demonstrate 10 GPa strength of polymer nanofibers [Shrestha, Shen, de Boer et al., 2018].

Microtensile test systems

This is an on-chip microtensile test system. It enables rapid measurement of strength at the micron scale. By taking over 200 strength measurements, we showed [Saleh, Beuth and de Boer, 2014] that the lower value of polycrystalline strength is about 2 GPa - greater than high strength steels, which are up to about 1 GPa.

Microrelays

A microrelay device is pictured at left. Such devices are being used as replacements to transistors in radio frequency communications. A critical issue is the growth of a friction polymer, which increases its electrical resistance. We studied materials and environments to understand the cause of friction polymer growth, how it becomes converted to a graphitic material and how to minimize it [Brand and de Boer, 2013]. We also focus on new materials for microrelays [Oh and de Boer, 2019].

Nanorelays

Fabrication of the nanodevice at right was lead by David Czaplewski when Maarten still worked at Sandia Labs [Czaplewski, de Boer et al., 2009]. Such devices are being considered as complements to transistors in computing. A device we recently reported on with the Piazza group is described here.

Microcantilevers

While the cantilever structure is simple, it is powerful for testing and understanding the contributions of van der Waals [DelRio, de Boer et al., 2005] and capillary [Soylemez and de Boer, 2017] forces to adhesion ;In current work, we are building metal cantilevers to make fundamental adhesion measurements for nanoswitches.

Metrology and Test Chambers

The performance of many materials depends on temperature, gas environment and relative humidity. We build test chambers (e.g., [Soylemez, de Boer et al., 2013]) to control these factors.

Research team

Deepak Kumar

Post-Doctorate

MD Shariful Islam

Doctorate

Jose Loli

Doctorate

Co-Advisors

Jack Beuth

Bryan Webler

Research interests

High entropy alloy development for high temperature oxidation resistance; additive manufacturing of metals with powder-bed and powder feed systems

Email

jloli@andrew.cmu.edu

AJ Stair

Doctorate

Co-Advisors

Jack Beuth

Bryan Webler

Kyle Schneider

Doctorate

Co-Advisor

Michael McHenry

Past Ph.D. students

• Sid Hazra (2010, Ostendo)
• Vitali Brand (2014, Lam Research)
• Emrecan Soylemez (2014, Marmara University, Turkey)
• Mohamed Saleh (2015, Prince Mohammad Univ., Saudia Arabia)
• Sameer Shroff (2015, Bettis Labs)
• Changho Oh (2018, Lam Research)
• Ramesh Shrestha (2018, KLA)
• Prince Singh (2019, Bosch India)
• Longchang Ni (2021, Intel)
• Nick Jones (2022, Vulcan Forms)

Courses

Current courses

Course	Course Name	Location	Units	Semester Offered
24-652	Special Topics: Mechanical Properties of Engineering Materials	Pittsburgh	12	Fall
24-251	Electronics for Sensing and Actuation	Pittsburgh	3	Fall, Spring
24-651	Material Selection for Mechanical Engineers	Pittsburgh	12	Spring
24-751	Introduction to Solid Mechanics I	Pittsburgh	12	Fall
24-221	Thermodynamics	Pittsburgh	10	Fall
24-351	Dynamics	Pittsburgh	10	Fall
24-652	Special Topics: Mechanical Properties of Engineering Materials	Pittsburgh	12	Fall

Publications

For a list of Maarten de Boer's publications, please see the following: 

• Google Scholar
• Researcher ID
• Orcid

Media mentions

CMU Engineering

Tantalizing tantalum actuators and sensors

Can this refractory metal be an efficient substitute material in microelectromechanical system (MEMS) thermal actuators?

Mechanical Engineering

Driving ahead

From ensuring the supply quality of powertrain plastics to project managing Ford's new electric pickup truck, master's alumna Stephanie Jennings is applying the analytical and problem-solving skills she learned in MechE to her career.

CMU Engineering

A big comeback for a little switch

Maarten de Boer and Gianluca Piazza are developing reliable, mechanical switches the size of a DNA molecule, thanks to a $2M LEAP-HI grant from the National Science Foundation.

Journal of Applied Physics

de Boer's article featured on journal cover

A paper by MechE’s Maarten de Boer was featured on the cover of Journal of Applied Physics. It was also promoted as an Editor’s Pick and will be displayed on the journal’s homepage.

See More Mentions

Singh wins fifth preliminary round of 3MT

MechE Ph.D. candidate Prince Singh, advised by Maarten de Boer, was the winner of the CMU Libraries’ Three Minute Thesis (3MT) fifth preliminary round. The internationally recognized competition challenges Ph.D. students to consolidate their research projects, goals, and ideas in a three-minute oral presentation. The final competition will be help on Tuesday, March 26 in Kresge Theater in CFA at 4:30 p.m. 

Mechanical Engineering

Exploring high-entropy alloys

Collaborators De Boer, Poczos, and Webler receive a Manufacturing Futures Initiative (MFI) award to explore high-entropy alloys, a new class of metal alloy.

CMU Engineering

A high-tech spin on spider silk

This game-changing technology can transform polymers from soft and thermally insulating materials to an ultra-strong and thermally conductive material.

Mechanical Engineering

Engineering students and Congressman Doyle explore the role of tribology in industry and the economy

This semester, Carnegie Mellon University students had the opportunity to share tribology research projects with United States Representative Mike Doyle as part of the course, Material Selection for Mechanical Engineers.

Mechanical Engineering

From earthquakes to micromachines

Carnegie Mellon University Ph.D. alumnus Sameer Shroff and Professor Maarten de Boer published two companion papers detailing their research on micromachine friction.