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Digest This!


Digestion simulation and pill design activities courtesy of, Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder


Students in grades 6 – 8 reinforce their knowledge of the human digestive system and explore the concepts of simulation and the engineering design process by developing a pill coating that can withstand the churning actions and acidic environment of the stomach. Teams test the coating’s durability by using a clear soda to simulate stomach acid.

Grade level: 6 -8

Time: 20 minutes for the digestion simulation, 50 minutes for the pill design.

Engineering Connection
Engineering analysis and design.
A surprising amount of design goes into developing pill table coatings and the systems that apply them. Varying the coating’s material or thickness can dramatically change a medication’s effect on the body. Engineers play an integral role in the process, from developing and testing chemicals for coatings to designing the complex systems used to mass produce uniformly coated pills.


Learning objectives
After doing these activities, students should be able to:
  • Define “simulation” and explain its importance in the science and engineering fields.
  • Describe how simulation is used to test the human body’s reaction to medication.
  • Describe the function of the stomach in the human digestion process.
  • List several fluids our bodies use to digest food and understand how engineers simulate these fluids to perform experiments.
  • Explain how engineers can directly and indirectly help people who are suffering from medical issues, specifically those relating to the digestive system.
Learning Standards

International Technology and Engineering Educators Association (ITEEA)
  • F. Manufacturing systems use mechanical processes that change the form of materials through the processes of separating, forming, combining, and conditioning them. [Grades 6 – 8]
  • H. The manufacturing process includes the designing, development, making, and servicing of products and systems. [Grades 6 – 8]
  • H. Biotechnology applies the principles of biology to create commercial products or processes. [Grades 6 – 8]
  • G. A wide range of specialized equipment and practices is used to improve the production of food, fiber, fuel, and other useful products and in the care of animals. [Grades 6 – 8]
Next Generation Science Standards  
Matter and its Interactions
  • Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. [Grades 6-8]

Engineering Design

  • Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.
  • Analyze data from tests to determine similarities and differences among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.
  • Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

Common Core Mathematics Standards

  • Understand the concept of a unit rate a/b associated with a ratio a:b, and use rate language in the context of a ratio relationship. For example, “This recipe has a ratio of 3 cups of flour to 4 cups of sugar, so there is 3/4 cup of flour for each cup of sugar.” [Grade 6]
  • Develop a uniform probability model by assigning equal probability to all outcomes, and use the model to determine probabilities of events. [Grade 7]

Demonstration/Simulation of Digestion

In advance, gather materials for a class demonstration: 1 uncoated aspirin tablet [really inexpensive “uncoated” generic aspirin works best] and 1 enteric-coated aspirin tablet; two clear plastic cups; 1 cup vinegar; 1.5 teaspoons baking soda; pinch of salt; half cup water.

Engineering connection/motivation
Did you know that biomedical engineers recently created the world’s first artificial stomach? (Image, below.) It mimics many of the activities that take place in your body and can even throw up!
You might be wondering what anyone would want to do with a machine that works like a digestive system and throws up on occasion. In reality, this machine is expected to be very beneficial to scientists, doctors, and pharmacists who want to know more about how our bodies work. artificial stomachWhat happens to your food or medicine after you swallow it? How does your body absorb food or medicine into your system? This is very important to know!
One way this new machine benefits people is by helping doctors and researchers understand how fast certain foods are digested by the body and absorbed into the blood stream. This could lead to improvements in the understanding and treatment of diabetes and other diseases.
Biomedical engineers are continually researching and designing new types of medical devices to help doctors and other medical professionals help people. Many of the most revolutionary medical devices were developed by biomedical engineers.
Today, we want to think specifically about what types of environments biomedical engineers might try to simulate (imitate) in order to better understand what happens in our bodies. Can you think of some examples? (Possible examples: simulating blood flow around a blocked artery; simulating the digestion of a food or medicine; simulating the mending of a broken bone; simulating the absorption of a poison or harmful substance by your skin, lungs or digestive system; simulating the healing of a wound; etc.)
Let me demonstrate how a biomedical engineer might use simulation (mimicking real life processes) to better understand how a medication is processed by the body
Click HERE for demo directions and teacher resources.
aspirin demo

Protect that Pill Activity

The design challenge.

Sarah is a fifth-grade student with an extremely sensitive stomach that is irritated by certain foods and many medications. She recently came down with an illness that caused a high fever, among other symptoms. Her mother wants to help  fight the fever by giving Sarah some aspirin, but she is afraid that the medicine might make cause a stomach ache. Can you think of some ways you might be able to help Sarah?

(Possible answers: Have Sarah take the medication with food, use a different type of medication that does not cause stomach pain, use a coated aspirin, drink fluids and take a cooling sponge bath, have Sarah take the aspirin with another type of medication that helps stomach pain, etc.)

Many medicines help our bodies fight sicknesses and diseases, but can also make our stomachs hurt. Can anyone tell me where the stomach is in the digestive system and what it does? (Refer to the Teacher Background information in the TeachEngineering Digestion Simulation lesson.)
To prevent this stomach pain while still allowing the medication to get into our bodies, engineers and pharmacists have developed pill coatings that do not dissolve until after they have passed through our stomachs. These specially-coated pills are called “enteric-coated” pills or tablets.
Today, we are going to help Sarah by acting as engineers and developing our own “enteric” coating. We will create a recipe for our coating, and then test it by observing its effectiveness in protecting a piece of candy placed in an environment that simulates the stomach’s. Before we get started, why is it better to test the pill in a simulated environment rather than testing it on a human? (Possible answers: The coating could fail and make the person’s stomach hurt, it is easier to observe how the pill dissolves in the simulated environment, etc.).
Then, just like engineers, we will analyze our coating and make suggestions for improvements to our design.


For each group:

Before the Activity

  • Gather materials and measure specified amounts of flour, corn starch, sugar and vegetable into individual bowls.
  • Make enough copies of the Recipe and Fraction Worksheet to provide one per person.
pill activity figure 1

Figure 1: Activity set-up

    1. Divide the class into groups of two or three students each.
    2. Pass out worksheets and materials to each group (see Figure 1).
    3. Discuss with the class the different properties of each ingredient. Oil helps the dry ingredients stick together, helps make the mixture less sticky, and makes the coating less soluble. Flour and cornstarch are thickening agents with fairly similar properties. They also improve the workability of the overall mixture. Sugar thickens the mixture to some extent and makes the texture grainier, but can also make it less soluble when used in the right proportion, thereby improving its performance as a protective coating.
    4. Before any mixing is done, have student teams decide amongst themselves how much of each ingredient (in spoonfuls) they think they want in their coatings. These become their recipes, which they document on their worksheets.
    5. Following their recipes, direct students to begin mixing their coatings on paper plates (see Figure 1). If a team feels that more of a certain ingredient is called for, have them carefully measure it and add it into the mixture, remembering to make the changes to the recipe on their worksheets.
    6. When a group has finished creating their coating mixture and recipe, have them apply the coating to a piece of candy (see Figure 2). Encourage students to make a thin and sleek design so the pill is easy to swallow, inexpensive to ship, and requires less packaging.

Figure 2: Coated candy "pill" ready to test.

Figure 2: Coated candy “pill” ready to test.

  1. When all of the groups are finished, have a representative from each bring their coated candy to the front of the class. For each team, fill a plastic glass half full with clear soda, plus one extra cup of clear soda for an uncoated piece of candy (so students can see their coatings’ effect on the dissolving rate of the candy). Label the cups with a marker so each group’s cup can be easily identified.
  2. With the timer read, at the same time have students drop their coated candies into their cups of clear soda while the teacher drops an uncoated candy into a cup of clear soda as a control (Figure 3).

    pill activity figure 3

    Figure 3: Coated candy control

  3. Allow the candy to sit in the soda for 10 minutes (see Figure 4). After several minutes, if the coatings do not look like they are dissolving, have one student from each group stir their coated candy in its soda cup until the 10 minutes is over. Ask students: How does this step simulates a pill going through the human digestive tract? (Answer: This simulates the acidic environment of the stomach, as well as its churning and agitating movement.) Why is it better to test the pill in a simulated environment rather than testing it on a human? (Possible answers: The coating could fail and make the person’s stomach hurt, it is easier to observe how the pill dissolves in the simulated environment, etc.).

    pill activity figure 4

    Figure 4: After 8 minutes

  4. While waiting, keep students busy with another class activity or by having them draw ads that describe the benefits of their pill coatings.
  5. After 10 minutes have passed, have students remove their pieces of coated candy from the soda-filled cups (see Figure 5). As a class, make observations about which coating did the best job of protecting the candy “pill” and compare the coating recipes for each group to see what did and did not work. How did the coatings perform, compared to the uncoated control “pill,” and compared to the various team recipes?

    pill activity figure 5

    Figure 5: Comparing results

  6. Have students calculate on their worksheets the fractions represented by each ingredient in their recipes. Compare recipes among teams, and discuss as a class, as described in the Assessment section. What are the relationships between performance and proportion of certain ingredients? What are the advantages and disadvantages of using certain materials?
  7. Using what they learned from analyzing the testing results and original recipes, direct each group to write down a new and improved coating recipe.
  8. Following their new recipes, have each team mix up a new coating batch. Do not allow them to make changes to their recipes during this stage.
  9. Repeat the same procedure for coating and testing, and then compare the results again as a class. What improvements were made?
  10. Conclude by reflecting on the activity in terms of the universal steps of the engineering design process: Ask, Imagine, Plan, Create and Improve, as described in the Assessment section. These are the steps engineers go through in designing new products and processes.

Safety issues

The activity materials have the potential to be extremely messy, so emphasize cleanliness and keep cleaning materials nearby. Consider laying down newspaper on and around the desks as protection from spills.

Troubleshooting Tips

  • To make very sticky concoctions more workable, add extra flour or corn starch.
  • To prevent students from making a super-thick coating, set a limit on the maximum thickness permitted. Constraints like this are typical in real-world engineering design projects.


Pre-Activity Assessment

Class Discussion: Have students discuss which foods or medications make their stomachs hurt, such as spicy foods or aspirin, and suggest possible solutions, including taking pills with food.

Activity Embedded Assessment

Recipe Analysis: Have students calculate on their Recipe and Fraction Worksheets the fraction of the entire coating represented by each individual ingredient. Have teams compare their recipe breakdowns, looking for relationships between performance and the proportion of certain materials in the recipe. Discuss with the students possible drawbacks or advantages to using a higher proportion of certain ingredients, aside from the coating’s performance during the test phase.

Post-Activity Assessment

Class Discussion/Design Process: List all of the steps in the engineering design process as a class: Ask, Imagine, Plan, Create, Improve. The Museum of Boston’s Engineering is Elementary website has a .pdf graphic for use as an overhead transparency or slide. As a class, discuss what goes on during each step of the process and relate each step to some part of the activity just performed. (Example: Ask – in this step, we talked about a problem and asked everyone how stomach pain has been treated in the past.)

Activity Extensions

  • Have students research the different materials used as pill coatings and the different mechanical systems used to coat pills.
  • Redo the experiment and challenge the students to design their coatings based on taste, marketability, cost and ease of shipping and handling while still meeting a certain benchmark protection time (such as 10 minutes, 15 minutes, etc.) during the test phase.

Activity scaling

  • For lower grades, eliminate one or two of the dry ingredients to make the recipes simpler.
  • For upper grades, add additional ingredients such as salt, corn syrup, or water to make the recipes more complex. Lead a discussion to explore why certain items were better pill coating ingredients than others and try to determine what function each ingredient served.
  • For upper grades, turn this activity into a competition by challenging each group to make their pill dissolve at a specified time (that is, not too early and not too late).

Additional Resources   pill supercell_tablet_coater

Human Digestive System. Bobbin Cave’s kinesthetic anatomy lesson has kids act out the function of organs and cells in the gut as food particles come to them.
A Gut Issue: Measuring Iron Bioavailability. Agricultural Research Service newsletter on in vitro simulation.(1999)
The Human Gastrointestinal Tract. Quick primer from biology professor John Kimball’s online Biology textbook.
How It’s Made: Pills Discovery Education video [YouTube 4:51]
Protective Pill Coatings. A brief explanation and photos from Spectrascopy NOW.
Tablet Manufacturing Process, Part A [8:53] and Part B [5:15] YouTube videos

Activity photos © 2008 Jacob Crosby, ITL Program, University of Colorado at Boulder.

Activities © 2008 by Regents of the University of Colorado; Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder.

2 Responses to “Digest This!”

  1. I was reading the activity “Digest This!” and I would like to do it in my classroom. However, I would like to begin with the DEMO activity; uncoated aspirin vs enteric coated aspirin. Yet the demo activity cannot be found…. when I click on the link it indicates that the information is not there. Would it be possible for you to email me the directions for the aspirin demo activity? Thank you.

  2. The link has been fixed! got a major overhaul, including alignment of activities with common core mathematics and next generation science standards, so some of the web addresses may have changed. The DEMO activity can be accessess at

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