Engineering: Biomedical Engineering: Prosthetic Hand Design Worksheet

Question 1

A prosthetic hand is a device that helps replace some functions of a missing or injured hand. List three tasks a middle school student might want a prosthetic hand to help with during a normal school day.

Accepted Answer

A student might want a prosthetic hand to help hold a pencil, carry a lunch tray, open a locker, type on a keyboard, or grip a water bottle. Good answers identify specific school-day tasks that require hand function.

Question 2

Biomedical engineers begin by understanding the user. Write two design criteria and two constraints for a prosthetic hand made for a 12-year-old student.

Accepted Answer

Possible criteria include that the hand should grip common objects and be comfortable to wear. Possible constraints include that it must be lightweight and fit within a limited budget. Criteria describe what the design should do, while constraints are limits the design must follow.

Question 3

A team is comparing three materials for the fingers of a model prosthetic hand. Cardboard is low cost but bends easily, craft sticks are stronger but harder to cut, and plastic strips are flexible but more expensive. Which material would you choose for a classroom prototype and why?

Accepted Answer

A strong answer gives a reasonable material choice and explains the tradeoff. For example, craft sticks could be a good choice because they are strong enough to grip objects, even though they are harder to cut. Cardboard could also be reasonable for an early prototype because it is cheap and easy to change.

Question 4

Look at a simple finger mechanism made from three cardboard segments connected by tape joints. A string runs along the front of the finger. When the string is pulled, the finger bends. Explain how this model is similar to how tendons help fingers move.

Accepted Answer

The string acts like a tendon because pulling it causes the finger segments to bend. The tape joints act like finger joints because they allow movement between the segments. The model is simpler than a real hand, but it shows how tension can create motion.

Question 5

A prototype hand can lift a 200 gram cup but drops a smooth marker. What does this test result suggest about the design?

Accepted Answer

The result suggests that the hand has enough strength to lift some objects but may not have enough friction or finger shape to hold smooth objects. The team should improve the grip surface or finger contact points.

Question 6

A prosthetic hand prototype has rubber bands that reopen the fingers after the strings are released. One rubber band is too weak, so the finger does not open fully. What change could improve the design?

Accepted Answer

The team could use a stronger rubber band, add a second rubber band, or move the rubber band attachment point to create more opening force. The change should help the finger return to its open position reliably.

Question 7

During testing, a model prosthetic hand picks up the following objects: tennis ball, pencil, paper cup, and small box. It fails to pick up a coin. Explain why picking up a coin may be harder than picking up the other objects.

Accepted Answer

A coin is small, thin, and flat, so the fingers may not be able to get underneath it or pinch it tightly. Larger objects give the hand more surface area to grip, which makes them easier to pick up.

Question 8

A team records grip test results for two prototypes. Prototype A lifts 4 out of 6 objects. Prototype B lifts 5 out of 6 objects but takes twice as long to put on. Which prototype is better? Explain using evidence and tradeoffs.

Accepted Answer

Prototype B may be better if grip performance is most important because it lifted more objects. Prototype A may be better if ease of use is most important because it is faster to put on. A good answer explains that engineers must compare tradeoffs instead of choosing only by one measurement.

Question 9

Calculate the success rate for a prosthetic hand that successfully picks up 9 objects during 12 trials. Write the answer as a fraction and a percent.

Accepted Answer

The success rate is 9/12, which simplifies to 3/4. As a percent, 3/4 equals 75%, so the prosthetic hand succeeded in 75% of the trials.

Question 10

A student sketches a prosthetic hand with five fingers, but all five fingers close at exactly the same time using one string. Name one advantage and one disadvantage of this design.

Accepted Answer

One advantage is that the design is simpler and may be easier to build because one string controls all the fingers. One disadvantage is that the fingers cannot move independently, so it may be harder to grip objects with unusual shapes.

Question 11

Engineers often use iterative design. Put these steps in a logical order: improve the prototype, identify the problem, test the prototype, build a prototype, brainstorm possible solutions.

Accepted Answer

A logical order is identify the problem, brainstorm possible solutions, build a prototype, test the prototype, and improve the prototype. This order shows the basic engineering design process.

Question 12

A user says, 'The hand works, but it hurts my wrist after a few minutes.' What design issue is the user describing, and what is one possible improvement?

Accepted Answer

The user is describing a comfort or fit problem. One possible improvement is to add padding, adjust the strap location, reduce the weight, or change the shape so pressure is spread more evenly on the wrist.

Question 13

A prosthetic hand prototype has a palm that is 10 centimeters long and a thumb that is only 1 centimeter long. Why might this thumb design make gripping difficult?

Accepted Answer

The thumb may be too short to press against the fingers and hold objects securely. In many grips, the thumb provides an opposing force, so it needs to be long enough and placed well to help pinch or wrap around objects.

Question 14

You are asked to design a test for how well a prosthetic hand can grip different shapes. Describe a fair test using at least three objects and one measurement you would record.

Accepted Answer

A fair test could use the same hand, the same user, and the same number of trials for each object. The objects might include a ball, a pencil, and a cup. A useful measurement would be the number of successful lifts out of five trials or the time needed to pick up each object.

Question 15

A class wants to improve the grip pads on a model prosthetic hand. They can choose smooth plastic, felt, rubber, or aluminum foil. Predict which material will likely provide the best grip and explain why.

Accepted Answer

Rubber will likely provide the best grip because it usually has high friction and can slightly conform to an object's surface. Smooth plastic and aluminum foil may be slippery, while felt may help but can wear down or slide depending on the object.

Sign in to save

Sign in to save

Engineering: Biomedical Engineering: Prosthetic Hand Design

Related Tools

Related Labs

Related Infographics

Related Cheat Sheets

More Engineering Worksheets

More Grade 6-8 Worksheets