Multidisciplinary Curriculum in Sensor Materials

AKBAR, Sheikh, DUTTA, Prabir, WANG, Yunzhi, PATTON, Bruce & MADOU, Marc

Center for Industrial Sensors and Measurements (CISM), The Ohio State University, 291 Watts Hall, 2041 College Road, Columbus, OH 43210, USA, http://m04.cism.ohio-state.edu/nsf-crcd; www.cism.ohio-state.edu

1 Background and Vision

There is an increasing need for sensors to monitor industrial processes for improvement in product quality as well as the environment. Where sensor technology has been applied many benefits have resulted, including improved energy efficiency, better quality, lower scrap or off-specification products, and reduced emissions. Under the umbrella of the NSF Center for Industrial Sensors and Measurement (CISM), a research and development program for harsh environment sensors is being actively pursued at The Ohio State University (OSU). [1-4] Research teams include students and faculty from Departments of Chemistry, Physics, Materials Science and Engineering, Electrical Engineering, Industrial Engineering, and Mechanical Engineering. Efforts are now underway to embrace the field of Bio-MEMS, "electronic nose" and sensor arrays.

CISM's organizational structure provides a framework for interaction of scientists, engineers, students, and business leaders. Students from various disciplines closely interact with each other, as well as with scientists and engineers from industries and national laboratories. Exploiting the collaborative environment of CISM combined with research advances in sensors, we have started to develop an innovative classroom and industry-oriented curriculum. The curriculum is designed around the multidisciplinary approach of CISM and focuses on an interactive approach emphasizing problem solving, group work, communication, and industrial experience. CISM objectives stress the 21^st century workers need for skills beyond the technical, such as management, leadership, and ethics. Plans include expanding the students' technical education to include business, management, administration, and law. Emphasis will be on such issues as product design and liability, problems created by new technologies, protecting intellectual property, technology transfer, and the relationship to the Internet.

A three-course sequence (9 credit hours) in sensor materials including instructional laboratories with industrial experience for senior undergraduate and starting graduate students are being developed. Students taking this sequence along with 11 credit hours of relevant courses in participating departments including Business and Law will have the option to receive a minor or certificate degree program in "Sensors and Measurements". Figure 1 summarizes the essential components of the proposed curriculum.

2 Integration of Research and Education

A research program integrating basic science and engineering development in a highly interactive environment is CISM's primary mission. An educational environment where students can continually assess how their research progress is achieving the stated goals will help develop skills useful for future careers. CISM has spawned several innovations in teaching an interdisciplinary topic such as sensors. These innovations range from web-based classes (e.g. visit http://www.biomems.net) and distant learning, to team teaching by CISM faculty. Recognizing the educational significance of these new approaches, CISM recently launched an innovative, team-taught, and industry-oriented curriculum emphasizing problem solving, group work, communication, and the use of multi-media technology for in-class demonstration. This initiative is being funded by the NSF-CRCD (combined research-curriculum development) program.

The three new courses are being designed around the multidisciplinary approach of CISM, and team-taught by faculty members from a wide range of disciplines. Students entering these courses will have senior or graduate standing in physical sciences or engineering disciplines. Given the interdisciplinary nature of the topic, these courses should attract students from various disciplines ranging from basic science to applied engineering. Assignments will be group efforts to ensure that students from different disciplines interact and learn from each other. Such interaction would be necessary to make up for any deficiencies in background required to take this course.

The first course covering basic scientific principles of sensor materials has been taught for the first time during the Spring Quarter, 1999. The actual lecture notes can be downloaded from the CRCD website, http://m04.cism.ohio-state.edu/nsf.crcd. The second course will cover applications and related technological issues. Both courses have a laboratory component.

The laboratory component has two major parts: (i) core experiments in a dedicated laboratory and (ii) demonstrations in various faculty research laboratories. The core experiments will demonstrate fundamental aspects of sensor fabrication, characterization and sensing mechanisms. For the demonstration part, students will have access to CISM laboratory facilities including a newly assembled hybrid electronics laboratory that houses the "electronic nose" (donated by Alpha MOS Co.) with software for artificial intelligence and pattern recognition. Other CISM facilities include powder processing and heat treating, gas sensor measurement setup, thick film deposition (screen printing and spin coating), and a wide range of electrical measurements & testing capabilities.

The third course will be group projects with participating industries. Group projects will target specific industries, identify a sensor need, develop a prototype and perform field-tests. Each project is a team effort involving multiple students working in close collaboration with a faculty adviser and an industry partner. An essential component of these group projects will be an Industry Internship where students spend an extended period at the industrial sites performing field tests.

These group projects will be an integration of what is already being carried out in CISM research as part of probe design and field-tests. CISM students have designed probes (Fig.2) for both CO and NO_x sensors and tested them in the Engine Emission and Diagnostics Laboratory at the Center for Automotive Research (CAR) at OSU. [5] This facility includes an FTIR analyzer (Nicolet, Rega 7000), which is capable of analyzing and quantifying 20 possible components of the gas mixture on-line while the engine is running.

The probes are installed in the tailpipe, right next to the inlet of the FTIR analyzer, downstream of the oxygen sensor and upstream of the three-way catalytic converter (Fig.3). The probes have been tested for many engine test cycles where they have survived the severity of the engine atmosphere so far. A typical response of a prototype YSZ-based NO_x sensor tested inside the exhaust manifold of a Ford V8 engine is shown in Fig.4, which shows the correlation between NO concentration, EMF value and temperature during the test period. In general, the sensor shows good response to NO concentration with a systematic deviation mostly due to the interfering gases. Its output signal was found to correspond well to the NO_x concentration in the rich-burn regime with known oxygen concentrations.

3 Integration of Computer Modeling

In view of the fact that computational science and engineering (CSE) is playing an increasingly important role in modern technological advancements, modeling and simulation of gas sensing processes in ceramic composites forms a key modulus of the curriculum. The research achievement on computer modeling and simulation at CISM is uniquely suited for adoption to undergraduate and graduate instructions because it involves the design and optimization of sensor materials and extensive visualization. [6,7] Both are topics of great interest and importance to undergraduates and graduates, but adoption of such techniques in academia has been slow because of the enormous time commitments required. The CRCD and CISM provide a synergy between research and instructional aspects because design and visualization techniques are inherently required by both.

Modeling and simulation is used in several ways in the course on sensors to integrate the interdisciplinary approaches and results from different disciplines, including chemistry, physics and materials science and engineering. These include both model building as a means of understanding the experimental results on sensors the students fabricated, as well as simulations which give the students experience with real life project-oriented design and optimization questions. First, realistic microstructures such as those found in gas sensors were simulated, with a typical weakly sintered porous microstructure shown in Fig.5. Then the experiments on actual sensors were analyzed, and models of the surface gas reactions, granular microstructure and interface barriers were developed. Parameters in the models were determined from experimental data. Finally, students used the models to design sensor devices with specified properties like linear or on-off response. Computer-based laboratories were developed in which students working in groups came up with optimal designs for given sensor applications.

In particular, in the computer-based modeling lab entitled: Gas Sensor Design by Computer, the students were able to control the sensing behavior by material and processing choices and see how the sensor responded to ambient gases. A typical model sensor response in anatase TiO₂ is shown in Fig.6 together with the experimental data. The students were divided into 4 groups and worked as a team to explore the features of the electrical conduction through a granular composite gas sensor. Each group was given a goal to design a ceramic gas sensor for CO detection with optimal response properties. A simplified version of our computer research code was installed in a computer simulation lab in the Physics Department, where 10 PCs are connected in a teaching network. The physical and mathematical models behind the programs were covered in the lectures. The students were given instructions on how to run the program, the input parameters and the output data in the lab. Then they were on their own to design two types of sensors: a linear gas sensor and an on-off gas sensor. They were required to optimize the performance of each sensor by adjusting the values of the input parameters including the desired microstructure, the desired surface chemical properties in terms of the energy levels, and the desired electrical properties of the grain and grain boundary regions. The modeling code was provided on-line so students could work at home or on other computers on-campus.

4 Interdisciplinary Honors Course

Further enhancing the NSF-CRCD program, CISM was awarded funding by OSU Honors House to develop a 5 credit hour interdisciplinary undergraduate honors course in "Sensor Materials". This course is planned for the first offering in the Fall of 1999. As shown in the course outline, this course will be an integration (literally, a condensed version) of the three-course sequence being developed under the CRCD program. This course has three parts: (i) lectures covering basic scientific and technological principles, (ii) laboratory experiments demonstrating fundamental aspects of sensor fabrication, characterization and sensing mechanisms, and (iii) group projects with industrial relevance.

4.1 In-Class Lectures

Introduction

• Technological needs and justifications

Synthesis and Fabrication

• Conventional synthesis
• Chemical synthesis
• Nano-phase materials
• Thick and thin films, MEMS

Surfaces, Interfaces and Catalysis

• Molecular recognition
• Chemistry and Defects
• Adsorption and desorption
• High-temperature catalysts

Characterization of Sensors

• Structure and microstructure
• Surface and interface
• Optical spectroscopy
• Electrical and sensing properties

Theory and Modeling

• Sensing mechanisms
• Microstructure evolution and its relationship to sensing properties
• Artificial intelligence and pattern recognition

Applications

• Automotive
• Aerospace
• Power and utility
• Manufacturing and process control
• Bio-medical

4.2 Instructional Laboratory

The instruction laboratory will encompass synthesis of sensor materials leading to sensor fabrication and characterization. Students will be required to submit a written report.

Novel Synthesis of Sensor Materials

High purity and high surface area powders of TiO₂, CaZrO₃ and Y₂O₃ will be prepared by sol-gel, hydrothermal and precipitation techniques. Such materials preparation promotes enhancement of selectivity of gas sensors, and controlled and homogeneous doping for thermistor applications.

Fabrication of Sensor Components

Synthesized powder will be used for thick-film sensor fabrication. Both the two-probe and four-probe dc measurements will be used to obtain the electrical resistance. The ac electrical data will be acquired with an impedance analyzer. Necessary electrical parameters will be extracted through a complex nonlinear least-square curve fitting software program developed at CISM.

Sensor Characterization

• Phase identification by XRD
• Microstructure chemical analysis by SEM and EDS
• Surface by Raman and Infrared Spectroscopy
• Sensor characteristics (sensitivity, response time, reversibility, recovery, etc.)

4.3 Group Projects with Industry

Group projects will be structured very similar to that of the CRCD program. Each project will be a team effort involving multiple students working in close collaboration with an industry partner and will develop a prototype sensor probe based on the literature (including patent literature) and prior CISM experience. Faculty at CISM have strong interactions with our industrial colleagues and will facilitate the interaction of students with industrial researchers. Students will be required to submit a written report and make an oral presentation on their projects. Examples of group project themes are shown in Table 1.

Table 1. Examples of group project themes and involved parties

5 Assessment Plans

Both the CISM University Policy Committee and the CISM Industrial Advisory Board will evaluate the program. They will advise and guide the faculty during the project development. An external committee consisting of representatives from academia, national laboratories and industries will also review the curriculum. A statistical survey done by specialists (i.e., from the OSU School of Education) will track students in the program. Students will be asked to complete a questionnaire, designed by an evaluation team, aimed at determining the success of the program in preparing them for their careers. Also, a web-based course evaluation will be developed to provide feedback and evaluation of the approaches and materials used in the course.

6 Dissemination Plans

The results of this project will be disseminated through three mechanisms. The first is the presentation and publication of papers describing the curriculum and its philosophy, together with a description of sample capstone design projects, and the participation of industrial sponsors in these projects. Papers will be presented at the Frontiers in Education Conference, and at other professional society meetings and symposia. For example, CISM faculty have presented this curriculum plans at: (1) the International Conference on Engineering Education (ICEE-98) [8], Rio de Janeiro, Brazil and (2) Innovation in Ceramics Education Symposium at the Americal Ceramic Society Annual Meeting, Indianapolis, USA, 1999.

The second means of dissemination is through a workshop held at the end of the project. The objective of the workshop will be to gather faculty and industrial participants to discuss the findings of the project and the impact and value to education.

The third means will be the establishment of an Internet site for computer-aided instruction and distance learning. Video and multimedia instruction will be developed and used as teaching tools. Moreover, the existing OSU distance learning system that connects classrooms to off-site participants will be used. This interactive television originating live from specially equipped classrooms will be videotaped and disseminated among participating universities. Course materials will be made available through Internet, videotapes and animation CDs. Some of these materials may appeal to the National Science Teachers Association (NSTA).

7 Participation of Women and Underrepresented Minorities

Special efforts will be made to encourage enrollment of women and minority groups. In fact, the OSU campus has a large minority student population (~ 7,000) and is rising steadily. This group will be targeted with incentives such as Undergraduate Research Scholarships through the Office of Research and the Women in Engineering program. Other minority groups will be targeted through distance learning and outreach programs. Initially, universities associated with the NASA Space Technology Development and Utilization program (STDP) will be targeted. Systematically, the program will expand to other schools. The STDP, an existing infrastructure, enhances and strengthens each University's science and engineering research program. It also helps increase representation of African Americans, American Indians and Hispanics in these fields. Working with the STDP focuses the infrastructure and provides for effective management and technical interfaces with organizations such as NASA program offices and field centers, minority academic institutions, the private sector and the minority business community. It is recognized that students learn differently, by utilizing multi-media it is anticipated that women and minorities may have a more "class room friendly" and better learning environment. This could lead to better recruitment and retention of these groups.

8 Aknowledgements

This program was supported by grants from the National Science Foundation (EEC-9872531 and EEC-9523358) and OSU Honors House.

References