Low-cost prosthetic arm

My role
Research assistant, Stevens Institute of Technology, summer 2024, under faculty supervision; continued through Avenues’ Mastery Program.
Year
2024
Type
Prosthetic arm, research
Status
Working build
Render of the prosthetic arm with a translucent forearm: a stack of servos, gears and a circuit board visible inside, white fingers above

Render of the whole arm: servo stack, gears and board through the translucent forearm.

  • 90+ prototypes, from PLA finger test prints to a full printed hand and forearm.
  • Servos in the forearm pull Kevlar cords to close each finger; elastic cords open it again.
  • Sized to the wearer: the parametric model is built on seven hand measurements.

A 3D-printable lower-arm prosthetic, hand and forearm, built from off-the-shelf parts, driven by servos through tendon-style cords, controlled by a myoelectric sensor, and sized to the wearer from hand measurements.

Results

prosthetic arm prototypes
90+prototypes
auto-sizing loop ceiling, reporting part mass per cell configuration
500iterations
hand measurements the parametric model is built on
7parameters

(Low-cost prosthetic arm)

Versions

  1. Finger prints

    PLA test prints of a finger, then an assembled gray printed hand.

    6 printed pieces and 2 pin rods per finger · finger part count

    An assembled gray 3D-printed hand, back view, fingers extended, print lines visible

  2. Parametric CAD

    Exploded parametric model on seven hand measurements across Digits 1–5.

    7 parameters · hand measurements the model is built on

    Exploded parametric CAD of the arm with construction sketches, datum lines and constraint points

  3. Final build

    White palm and glossy black forearm; hand, wrist collar and end plate print as separate segments.

    5 forearm subsystems · servos, wrist control, Arduino, batteries, myoelectric control

    The physical arm exploded on a light gray tray: white printed palm and fingers, glossy black forearm and wrist collar, loose knuckle caps and pins
The physical forearm standing upright with its shell opened: stacked black servos, red and black wiring, a green Arduino-style board, the white hand on top

The forearm opened

The forearm opened: servo stack, wiring, Arduino-style board.

The finished black printed hand seen from the back, five segmented fingers

The finished hand

The finished hand from the back, five segmented fingers.

Profile render of the finished arm: glossy black conical forearm and five white printed fingers extended flat

In profile

The finished arm in profile, fingers extended.

The seven hand measurements the parametric model is built onA drawing of a hand, palm side, with digits 1 to 5 labelled and each measurement marked as a girth arc or a length arrow.Digit 1Digit 3Digit 4Digit 2Digit 51234567
1
Hand circumference
2
Hand length
3
Palm length
4
Wrist circumference
5
Finger root circumference
6
Interphalangeal joint circumference
7
Distal interphalangeal joint circumference

The seven hand measurements that size the model, redrawn from the design brief.

How it works

One elastic cord holds the finger open; a Kevlar cord from a servo in the forearm pulls it closed. Elastic runs outside the bend, Kevlar inside.

Servo travelOne elastic cord holds the finger open; a Kevlar cord from a servo in the forearm pulls it closed. Elastic runs outside the bend, Kevlar inside. Servo travel 0 percent.
0%

The joint angles in this drawing are illustrative: they are chosen so the hand closes at full travel, not measured from the build.

A bent printed finger with the elastic cord path traced in red outside the bend and the Kevlar cord path in blue inside

From the design brief: elastic (red) and Kevlar (blue) paths.

Facts

My role
Research assistant, Stevens Institute of Technology, summer 2024, under faculty supervision; continued through Avenues’ Mastery Program.
When
Summer 2024, then continued.
With
Stevens Institute of Technology, faculty-supervised.
Status
Working build. Controls and size automation are still being refined.
Stack
Off-the-shelf parts, mostly 3D-printed; servos; elastic and Kevlar cord; EMG sensor; Arduino.
Awards
None.
Prototypes
90+.