Hands-on Activity: Designing a Medical Device to Extract Foreign Bodies from the Ear

Contributed by: Biomedical Engineering, University of Virginia

A cutaway medical illustration shows the pointed end of a pencil in a child's ear, lodged into the ear canal all the way to the ear drum. A photo shows a woman using a handheld device to look into a girl's ear.
How can we remove foreign objects from the ear?
Copyright © (top) ADAM Health Solutions, MedlinePlus, National Library of Medicine, National Institutes of Health, Department of Health and Human Services; (bottom) State of Oregon http://m.medlineplus.gov/ency/imagepages/19592.htm http://www.oregon.gov/OHLA/HAS/Pages/index.aspx


Students learn the engineering design process by following the steps, from problem identification to designing a device and evaluating its efficacy and areas for improvement. A quick story at the beginning of the activity sets up the challenge: A small child put a pebble in his ear and we don't know how to get it out! Acting as biomedical engineers, students are asked to design a device to remove it. Each student pair is provided with a model ear canal and a variety of classroom materials. A worksheet guides the design process as students create devices and attempt to extract pebbles from the ear canal.

Engineering Connection

The activity challenge is one that real-world biomedical engineers actually face. Students follow the steps of the engineering design process to design, build and test prototype medical devices. They are asked to think of what other materials could be applicable in this situation and what other principles engineers might need to consider to solve this problem. Similarly, engineers do research and review prior art before attempting to solve problems. Students also learn about engineering a bit beyond the obvious. For example, they may not have all the materials they want or a classmate may have used the last bit of glue, so they are faced with limitations. Engineers rarely have all the resources they want to solve problems. Limits on technological capabilities, funds and time require creativity and teamwork to overcome.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

Suggest an alignment not listed above

Pre-Req Knowledge

Familiarity with human ear anatomy and function. A good resource to learn this is HowStuffWorks.com's page titled, "Why do loud noises cause your ears to Ring?"

Learning Objectives

After this activity, students should be able to:

  • List the steps of the engineering design process.
  • Describe the work of biomedical engineers and give examples.
  • Draw at least one connection from a science class lesson to the work of engineers.

Materials List

Each group needs:

  • model ear canal (see attachment on how to assemble)
  • 1½'' clay pot (available at crafts stores)
  • 1½'' PVC pipe connector (available at hardware stores)
  • plastic tubing ½'' outer diameter, 3/8'' inner diameter (available at hardware stores)
  • o-ring to fit over ½" plastic tubing (such as Danco #8, available at hardware stores)
  • vegetable bag from grocery store (only 2 or 3 are needed per class)

For the entire class to share. (You may not need all items; most are available from crafts or drug stores)

  • small pebbles (required)
  • popcorn kernels (required)
  • clay
  • glue dots
  • scissors
  • pipe cleaners
  • rubber bands
  • glue (rubber cement, hot glue, Elmer's glue)
  • dowel rods (big and little)/small sticks
  • miniature clothes pins
  • paper clips
  • wire
  • small fuzzy pom poms, or other small fuzzy object
  • tape
  • tweezers
  • magnets
  • oral syringes (available at drug stores)
  • any other classroom items or small item that could be included in the invention


(Picking up from where we left off in the associated lesson...) So now it is your turn to be biomedical engineers! We have a new problem. Let's pretend you have a little brother named Scotty. You and Scott are playing in the backyard in the summer and you run inside to get a drink of water. While you are gone, Scott remembers his crazy uncle telling him that if he put a rock in one of his ears, it would come out the other. You are all smart and know from studying the anatomy of the ear that this is NOT the case. Scott is really young, though, and doesn't know any better so he tries it. And guess what? It doesn't come out the other side. What worse is that he pushed it so far down in there that it isn't coming back out when he tilts his head to the side! He goes inside crying to your mom, your mom takes him to the doctor, and the doctor doesn't have any tools to get it out. SO you're the biomedical engineer!

Your engineering challenge is to design a device to extract the pebble from Scotty's ear. You should have a worksheet in front of you. Work through number 6, then go get materials to design the device you select. I will pass out the model ear canals and the rocks so you have them for reference.


constraint: A design equirement. It might be a quality, feature or specification the final design must have, contain or meet.



Small children are curious creatures. As a method of exploration, they often stick small objects in their noses and ears including beads, popcorn kernels, small sponges, toys and rocks. Currently, doctors have limited tools to extract these objects. Various tools—tweezers and hooks—and flushing methods are used, but spherical objects are difficult to grasp with tweezers and sponges just absorb water used for flushing! Biomedical engineers at the University of Virginia are currently developing a device that extracts all types of foreign bodies from ear canals. This activity asks students to design their own devices to solve this problem.

Before the Activity

  • Make copies of the worksheets and quizzes.
  • Assemble model ear canals; refer to the Teacher's Guide - Assemble Ear Model for instructions.
  • Make overhead slides of ear diagram and pictures of ear tubes and ear tube insertion device.
  • Put all class material out on a table.
  • Put a small rock in each model ear.

Prepare the class materials:

Shared materials—Collect these from available school supplies: clay, glue, pipe cleaners, scissors, Popsicle sticks, small dowel rods, glue dots. Obtain remaining items at crafts stores.

Team materials—for the model ear canal:

Clay pot used to model outer ear (right). Hole at the bottom of the pot is entrance to ear canal.
Copyright © Shayn Peirce-Cottler, University of Virginia

  • vegetable bags
  • 1½'' clay pots (see Figure 1), available at crafts stores for 50-60¢ each.
  • 3 items from hardware stores::
  1. rigid plastic tubing (see Figure 2), get plastic tubing with an outer diameter of ½'' and inner diameter of 3/8'', which is printed on the tubing and on signs above large rolls of tubes; ~20¢ per foot; usually located the PVC pipe section of the store; get ~3 feet
  2. o-rings (see Figure 2), such as Danco O-Rings, $1.20 for package of 10; get two packages of #8; usually located near the PVC and tubing section of the store
  3. PVC connector pipe (see Figure 3), used to simply hold the clay pot, size: ~ 2.5 inches tall and ~2 inch diameter; take a clay pot to the store and just make sure it rests properly

o-rings and plastic tubing needed to assemble model ear canal.
PVC pipe connector holds model ear canal.

With the Students

  1. As students walk into the room for clas, pass out the quizzes. Do this in the few minutes before the bell rings for class and as everyone settles in.
  2. After the lesson is complete, divide class into student pairs.
  3. Make sure students have the worksheets (should have been handed out during the lesson).
  4. Direct students to work through step 6 on the worksheet before choosing supplies to make their devices.
  5. As groups are working on the worksheets, pass out the model ear canals.
  6. While students are completing the worksheets and designing, circulate and answer questions and encourage creativity with the designs. Also, check the supply table regularly, reminding students to take only what is necessary and return to their seats to build.
  • After students successfully extract a pebble once, ask them to do it a second time. Repeatability is important in developing a reliable medical device.
  • After a successful second extraction, have students use their same device to extract a small fuzzy pom-pom and a popcorn kernel.
  • If they finish this, ask "Did you have any problems with your device?" or "How could you make your device better if you were to use it with a real person?" If students do not have materials available to make the changes they would like, ask them to list the materials and describe how they would make the changes on the worksheet.
  1. If a group punctures the ear canal, simply cut another from the veggie bags and replace!
  2. Towards the end of the design period, hand out the quizzes to be completed as homework.
  3. At the end of the design period, have groups describe their devices, explain a challenge or problem they had, and how it might be resolved with more time or different resources.


Safety Issues

  • Emphasize that the devices designed are strictly for use in the model ear canal, not in the ear canals of real people. These are prototype designs that have not been tested for safety.
  • Students should not put small rocks and other objects in their ears to see if they can get them out by tilting their heads to the side, or for any other reasons. Remind them to be smart about the activity!
  • Remind students that only trained healthcare professionals should stick things into their ears!
  • The following articles describe treatments for dealing with foreign objects in the ear. Q-tips should not be used to clean objects from inside the ear.
  • Ear Foreign Body Treatment from WebMD
  • EarWax from WebMD
  • All Ears: Q-Tips – Weapons of Ear Destruction? From WebMD

Troubleshooting Tips

If students have trouble starting the activity, work through the first few steps as a class.


Pre/Post Quizzes: As students enter the classroom, before starting the activity, administer the Pre-Assessment Quiz . At activity end, administer the same quiz. Compare student answers to gauge their changes in content knowledge.

Writing: Ask students to write answers to the following questions:

  • What are two examples of products designed by biomedical engineers?
  • How do engineers go about problem solving? What are the steps of the engineering design process.
  • What are two examples of how subjects learned in science or math class can be applied to engineering problem solving?

Activity Extensions

Think of other devices that biomedical engineers could design.

Think of other medical problems from your own experiences or the experiences of family and friends and discuss what engineers could design as solutions for those problems.


Ear Infections. Last Updated: March 16, 2010. MedlinePlus. Accessed March 28, 2010. http://www.nlm.nih.gov/medlineplus/earinfections.html
Engineering design process. Last Modified: March 26, 2010. Wikipedia. Accessed March 28, 2010. http://en.wikipedia.org/wiki/Engineering_design_process
Richardson, Karen. Miracles in the Making. Created Fall 2005. Wake Forest University Baptist Medical Center. Accessed March 28, 2010. http://www2.wfubmc.edu/MedicalCenter/news_templates/featured_article.aspx?NRMODE=Published&NRORIGINALURL=%2Farticles%2FMiracles%2Bin%2Bthe%2BMaking%2F&NRNODEGUID={696AB72B-0A8C-4983-8498-45E0246181C2}&NRCACHEHINT=Guest
Conger, Cristen. Why do loud noises cause your ears to ring? HowStuffWorks, Discovery Company. Accessed March 28, 2010. http://health.howstuffworks.com/loud-noise-ear1.htm


Shayn Peirce-Cottler; Leyf Starling; Derek Harbin; Krista Warner


© 2013 by Regents of the University of Colorado; original © 2007 University of Virginia

Supporting Program

Biomedical Engineering, University of Virginia


Created by students in Dr. Shayn Peirce-Cottler's biomedical engineering senior design course.