Remote Experimentation with MEMS Devices

Author(s):
Edward Kolesar - e.kolesar@tcu.edu
Bill Diong - Texas Christian University

Industry:
Imaging Equipment, Industrial Controls/ Devices/ Systems, University/Education, Research, RF/Communications

Products:
PXI/CompactPCI, LabVIEW, NI ELVIS

The Challenge:
Developing the means for a class of undergraduate students to conduct experiments involving unique and delicate instruments to characterize various given Micro-Electromechanical System (MEMS) devices.

The Solution:
Using NI LabVIEW and other NI software and hardware to enable student access over the Internet to command appropriate inputs to the MEMS device under test, and to capture data and images from the device.

Using NI LabVIEW and other NI software and hardware to enable student access over the Internet to command appropriate inputs to the MEMS device under test, and to capture data and images from the device.

Our goal was to enable students in the materials science course at Texas Christian University (TCU) to conduct an experiment via the Internet on MEMS devices located in a TCU research laboratory. A remote experimentation system based on NI hardware and software was developed and integrated in a timely and cost-effective manner. The students were subsequently surveyed concerning their experience, and the responses were overwhelmingly positive.

Introduction

Mid-way through the TCU ENGR 30014 materials science course, the students study the electrical and thermal properties of materials. The instructor decided it would be helpful for the students to conduct an experiment that served to demonstrate the synergistic linkage between these topics and illustrate the concept of device characterization. One possibility was to have these undergraduate students run experiments on MEMS devices to determine the in-plane tip displacement versus absorbed power characteristics of a MEMS electrothermal actuator. However, the risk of students damaging delicate and expensive instruments typically used exclusively for MEMS research was unacceptable.

Knowing that NI offers products that provide remote access to and data acquisition from test equipment over the Internet, we embarked on a project to enable our students to conduct an experiment via the Internet on electrothermal actuators located in the TCU MEMS research laboratory. This gave our students a unique learning experience, but imposed constraints on what they could do with the supporting equipment to minimize the risk of damage.

Experiment VI

An experiment VI was developed successfully by Jamie Smith, who was a senior undergraduate student at the time with no prior LabVIEW experience. The main functions of the VI that was developed include:

(i)    Apply a user-commanded voltage

(ii)   Capture images of the unpowered and powered actuator (so that its displacement can be determined by the user)

(iii)  Acquire and calculate the voltage, current, and power values associated with the MEMS device

(iv)  Plot the displacement versus power characteristic curve for the device under test.

NI ELVIS

NI Educational Laboratory Virtual Instrumentation Suite (NI ELVIS) was used as the hardware interface between the NI PCI-6251 data acquisition (DAQ) board and the MEMS device. The user-commanded voltage on the VI front panel was applied by the DAQ board via a power amplifier to the series connection of a resistor (so that the supplied current can be determined from its voltage drop as acquired by the DAQ board) and the MEMS device; therefore, the device’s voltage was actually somewhat less than the commanded voltage. The exact value was calculated by subtracting the voltage drop across the current sense resistor from the commanded voltage, and that device voltage value was then displayed with the device current and power values on the VI front panel.

Image Capture

The images of the unpowered and powered MEMS device, as captured by a video camera through a microscope, were embedded in the VI front panel.  Thus, an NI PCI-1405 board and the MeasurementAutomation Explorer (MAX) were used to perform the image acquisition by LabVIEW. 

Displacement versus Power Plot

Our solution to implementing the MEMS tip displacement versus power plot was to use shift registers rather than local variables. By using shift registers, we created the ability to append the new data to the old data for any desired number of points.

Remote Access

LabVIEW features the capability to have a VI viewed and controlled remotely over the Internet using a Web browser. Therefore, we published the MEMS experiment VI described above on the Web. Once the .htm file was available on the VI server PC, we were able to view and control the MEMS experiment VI front panel with a Web browser on a different PC. On some Windows PCs, we were unable to view (and therefore control) the VI front panel in the Web browser window, but this was easily remedied by installing the LabVIEW Run-Time Engine, which can be downloaded for free from the KnowledgeBase on ni.com.  

Access Limiting

Because the Web publishing tool described above does not allow the access limiting desired for this experiment (to prevent plagiarism), some modifications were needed.  With the built-in capabilities, either all users can view the VI front panel or none can.  But for our purposes, when one student is using the experiment VI, no other student should be able to view the first student’s work during his/her experiment. Our solution was to slightly alter the HTML code generated by the LabVIEW Web Publishing Tool and embed it in an ASPX file, which for security reasons resides on a gateway Web server for the TCU domain.

Conclusion

NI hardware and software was readily applied to implement a remote experimentation system that provides undergraduate students at TCU the unique opportunity to perform experiments on state-of-the-art MEMS devices while minimizing the risk of damage to delicate and expensive equipment. Furthermore, the students were surveyed concerning their experience, and the responses were overwhelmingly positive. We believe that our broader, long-term goal of enabling other TCU students to conduct experiments on systems located in any of the university’s science and engineering laboratories via the Internet is a step closer to reality.

For more information, contact:

 

Bill Diong

 

Texas Christian University

 

TCU Box 298640

 

Fort Worth, TX 76129

 

Tel: (817) 257-6317

 

Fax: (817) 257-7704

 

E-mail: b.diong@tcu.edu

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