Question

MEDICAL ADAPTIVE ENGINEERING:
PROSTHETIC HAND PROJECT
Instructions: Carefully read the following scenario, and then fill in the design brief.
DESGINING A PROTOTYPE PROSTHETIC HAND
BioMend Innovations, a cutting-edge adaptive medical tech company, has received feedback from its clients—many of whom are young, active individuals-about the need for a lightweight, easily adjustable prosthetic hand. The company wants a new prototype that not only replicates the basic grasping function of a human hand but is also comfortable to wear.
Functionality: The prosthetic hand must have at least three fingers that move. The fingers must open and close by pulling on a string (or similar mechanism). Wearability: The device must attach securely to your arm or hand in some way. It should be comfortable enough to wear for brief demonstrations. Material Usage: Use everyday, low-cost materials (e.g., cardboard, tape, straws, string, rubber bands). Demonstration: The hand must be able to pick up or hold a variety of objects (a ping-pong ball, a small paper cup, a pencil, an empty soda can, a full soda can).
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Overvien
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Confidentiall
1. Problem statement
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3.
4.
Criteria list
Constraints list
You can write the low-cost materials list and refer to it in your problem statement
Note: write and then as a team discuss the best one-Make sure everyone has the same problem statement and lists

Answer 1

Design brief — Prototype Prosthetic Hand (student / low-cost demonstrator)

1) Problem statement
Design and build a lightweight, low-cost prototype prosthetic hand that is comfortable to wear for short demonstrations and replicates basic grasping. The hand must have at least three movable fingers that open and close by pulling on strings (or a similar purely mechanical tendon-like system). The device must attach securely to a wearer’s forearm/hand (adjustable strap or sleeve) and be comfortable enough for a wearer to use for brief demos (~10–20 minutes). Use only everyday, low-cost materials (see materials list below). The prototype must be able to pick up and hold a variety of objects: ping‑pong ball, small paper cup, pencil, empty soda can, and a full (12 oz / ≈355 g) soda can.

Refer to low-cost materials list when planning construction and substitutions.

2) Success criteria (measurable)
- Minimum moving digits: at least 3 fingers that open and close under string/tendon control.
- Actuation: Strings or equivalent pull mechanism must reliably close all moving fingers when actuated by a single pull (or by simple multiple pulls) and reopen when tension released (with elastic return or passive reset).
- Object handling: The hand should successfully pick up and hold each of the five target objects in at least 3 out of 5 trials (repeatability).
- Load capacity: Grip must lift and hold a full soda can (~350 g) without slipping for at least 10 seconds.
- Wearability: Attachment must be secure for brief demonstrations — no major shifting or slipping during use. Comfortable for wearer for 10–20 minutes (no sharp pressure points).
- Weight: Prototype aimed < 500 g (adjust goal based on materials available).
- Adjustability: Attachment size/fit can be adjusted to fit a small range of forearm sizes (e.g., child to small adult) using straps/Velcro.
- Safety: No sharp exposed edges, no electrical components, and materials that won’t irritate skin during brief contact.

3) Constraints
- Materials: Use only low-cost, everyday materials (cardboard, tape, string, straws, rubber bands, etc. — see list below). No motors, batteries, or powered actuators; motion must be string/pulley/tendon-like mechanical.
- Cost: Target prototype material cost per unit under $20–$30 (adjust if school supplies already available).
- Time: Buildable within a typical class/after‑school project timeframe (2–4 hours for first prototype, with refinements later).
- Safety: Must be safe for a demonstrator to wear briefly (no sharp metal, no toxic glues in contact with skin).
- Complexity: Keep design simple enough for students to reproduce and adjust; avoid complex machining or specialized parts.
- Environment: Indoor demonstration only (avoid weather exposure).
- Durability: Adequate for repeated classroom demos but not required to last for months of daily use.

4) Low-cost materials list (examples / choices)
- Structural: corrugated cardboard, cardstock, craft foam, foam core, thin plastic sheet (from a folder)
- Finger cores / joints: drinking straws (outer/inner), folded cardboard strips, popsicle sticks, wooden skewers
- Tendons / actuation: string, twine, fishing line, strong thread, yarn
- Return/elastic: rubber bands, elastic cord, hair ties
- Fastening: hot glue, white glue, duct tape, masking tape, clear tape, paper fasteners/brads
- Attachment: Velcro strips, elastic band, cloth strap, neoprene sleeve or bicycle inner-tube strip, old glove or wrist cuff
- Reinforcement: small washers, cardboard reinforcement plates, zipties, binder clips
- Padding/comfort: foam padding, cloth scraps, felt
- Tools/supplies: scissors, craft knife, ruler, hole punch, pencil, hot glue gun (optional), pliers (optional)

5) Testing / demonstration plan
- Preliminary tests: check each finger’s range of motion and stiffness; ensure strings route smoothly through joints (straw channels or brads).
- Object tests: attempt to pick up each object in sequence (ping‑pong ball, paper cup, pencil, empty can, full can). Record success/failure and cause (slip, insufficient closure, attachment shift).
- Repetition: for each object perform 5 trials and record # successes.
- Adjustments: increase friction on finger surfaces (tape, foam) or add more fingers/contact points if slippage occurs; stiffen fingers or change tendon routing to increase closure force.
- Wearability check: have a team member wear the attachment for 10–20 minutes and report comfort / pressure points; adjust padding and strap placement accordingly.

6) Notes for team discussion and version control
- Draft several concise problem statements from the above and agree on one before building; this ensures everyone shares the same goals and acceptance criteria.
- Choose priority tradeoffs as a group: maximize grip strength vs. minimize weight vs. fastest build time.
- Record materials, dimensions, and a simple build log so other teams can reproduce improvements.

Suggested single-line problem statement to adopt during team meeting:
"Build a lightweight, comfortable, low-cost prototype prosthetic hand with at least three string-actuated fingers that can be worn for short demos and reliably grasp a ping‑pong ball, small paper cup, pencil, empty soda can and a full (≈355 g) soda can."

If you want, I can also produce a simple step-by-step build plan (materials layout, finger pattern, tendon routing diagram in words) for your first prototype. Which would your team prefer next?