Instructions

This challenge simulates a hiring problem set for a mechatronics/instrument device startup. It aims to assess your design thinking and application of physics and engineering principles.

Questions require written responses with sketches, and some may need CAD models (not in this set). You’ll typically have ~2 hours. These are designed so only top senior engineers would answer all perfectly—don’t be discouraged if it’s tough; use it to learn where you can still grow. If it’s not, you’re well-prepared!

Assume designs are for mass production and cost, assembly, and reliability needs to be considered. Sketches alone may not show subtle decisions—explain assumptions and reasoning for context. Try to show your work; sketches reveal your problem-solving process. This will be a great practice!

Question 1

There is a water-filled chamber with two hot plates directly beneath it, each equipped with its own cartridge heater and thermistor for independent temperature control. In order for certain reactions to happen, the chamber needs to have an area between 31±1C and 88±1C.

Assumption: Uniform and correct temperature in the hot plates. Only consider steady state. Don’t worry about the initial heating. The chamber is made out of acrylic.

Draw a simple sketch of what you would expect the temperature gradient to look like at steady state
Draw a simple sketch of what you would expect the zone of 32±1C and 88±1C would be located.
What would happen if the chamber was made out of the following materials instead?
1. glass
2. aluminum
In real life without making any assumptions, what can go wrong in this design? How would you mitigate it?
How would you optimize this design to maximize volume of 32±1C and 88±1C zones.

Question 2

Assess the design’s strengths and weaknesses, highlighting any critical flaws or benefits.
Suggest potential improvements to enhance the system.
Identify possible second-order effects that may need further analysis or testing.

Question 3

A future prototype needs a subsystem to deliver even clamping pressure to an assembled consumable with this geometry. There is a 2mm zone between the raised and lower surfaces where clamping pressure isn’t required. The thickness of the parts are irrelevant. Let’s assume that they have stainless steel backing.

The requirements are as follows:

The system needs to apply 15 PSI evenly across the entire surface of 1 sq in
The force distribution across the area needs to be less than 2 lbf.
The system goes through 1 million cycles of heating and cooling between 120 F to 35F.
This clamping system needs to be completely automated.

Design a high-level system design that would achieve this. Also, How would you verify that the requirements are being met?

Question 4

There is an optics system with a camera and LED illumination source mounted on a linear actuator. The camera subsequently takes images of samples at 4 stations every 30 seconds.

Once all components were installed, you began gathering images. However, the image captured at station 1 is blurry. Identify all potential reasons that could lead to this issue.
Drawing from your responses to question 1, how would you enhance the design or reduce the associated risks?

Resources