Create a Pill Coating

Introduction & Motivation

One of the largest fields of chemical engineering is working with medicines or treatments for illnesses. Engineers in this area can do anything from adjust the molecules that form drugs used to treat patients to improve the ways we deliver those drugs. Many constraints are involved with this work! Often, medicines have less than pleasant side effects on the body or taste truly terrible. Sometimes medicines are created and can be successfully delivered to the patient’s body, but have to be carefully stored to keep from contaminating or deactivating the drug.

This area of chemical engineering highlights how important it is for engineers to be able to understand the reactions and systems they work will to a degree that they can control them and achieve a certain goal.

For this activity, imagine that your friend is sick and needs to to take a pill to help with the symptoms. The pill dissolves instantly and releases the drug, but to be effective it needs to reach the stomach before dissolving. It is your job to develop a pill coating to cover a candy or alka seltzer “pill” that will delay the dissolving of the pill for a few minutes until it reaches the stomach.

Design goals:

  • The coating must be edible
  • The coating must prevent the pill from dissolving for at least 10 seconds and from then on slow the rate of dissolution
  • The coating must cover the pill completely, but not make it too large to swallow

**Tip! Try posing to the students what they think are important qualities of pills. This should help them formalize some design goals, and the leaders of the activity can flesh out the rest of the list. Be sure to write this on a board for reference during the activity!**

Materials

  • Cornstarch
  • Flour
  • Vegetable Oil
  • White sugar
  • Water
  • Vinegar
  • Alka Seltzer tablets
  • Smarties candies
  • Skittles candies
  • Stopwatches
  • Plastic Cups

**Tip! Buy lots of vinegar. Once the pill is dissolved, the solution is no longer clear and students tend to discard it.**

Procedure

Explain how the setup mimics the human body. Our stomachs are full of acid which help us to digest and absorb useful compounds from the food we eat. In this activity, the stomach is represented by a cup of vinegar. The viability of the pill in the context of the design goals will be tested by formulating a pill coating, wrapping it around a readily dissolving candy or tablet, and recording how long it takes for the pill to dissolve.

  1. For a control, dissolve the “pill” (either the candy or alka seltzer) in a small cup of vinegar to represent the acidity of the stomach and record the time at which the pill begins to dissolve as well as how long it takes the pill to completely dissolve.
  2. Work with your group to formulate ideas for pill coatings.  Make to record the amounts of each ingredient you use to make a recipe. Be sure the coating is relatively thick, and covers the entire pill.
  3. One the coated pills are ready, place a pill in a cup of vinegar and once again measure the time at which it begins to dissolve and the amount of time it takes to dissolve completely.

Discussion

  1. After the students have explored pill coatings, ask what they found was the most effective recipe for a pill coating. Did they have a certain method of putting it on the pill that helped?
  2. What might some more considerations of pill coatings be? (Taste, color, markings)

Additional Resources

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