Project Overview – Octopus Gripper

A soft robotic gripper inspired by octopus tentacles, designed as a modular end-effector for the UR3 robotic arm. The operator controls the gripper intuitively by bending their fingers while wearing a glove equipped with flex sensors. Bending a finger causes the corresponding tentacle to replicate the motion in real time via Bluetooth Low Energy, no cables between glove and gripper.

Each tentacle is printed in TPU 95A with 12 segmented vertebrae and a Dyneema tendon through the central channel. The servo pulls the tendon bending the tentacle up to 120°. Two independent microcontrollers: an XIAO ESP32-C6 on the glove (TX) and an XIAO ESP32-C6 on the gripper (RX). Both communicate exclusively via BLE.

System Integration Diagram

The diagram below shows how every subsystem merges and interacts — from the flex sensors on the glove, through the BLE wireless link, to the servo-driven tentacles mounted on the UR3 arm.

System Diagrams

The project is divided into two independent systems that communicate wirelessly via BLE.

Gripper System

Gripper side: 3 TPU tentacles + SG90 servos — PCA9685 16-ch PWM driver — custom PCB (XIAO ESP32-C6 RX) — DC bench power supply.

Glove System

Glove side: 3 flex sensors — custom PCB (XIAO ESP32-C6 TX) — MT3608 boost converter (3.7V → 5V) — LiPo 3.7V 1000mAh — rocker switch — 3D-printed enclosure on work glove with velcro.

Signal path — full system

How every subsystem connects, from flex sensors on the glove through BLE to the servo-driven tentacles on the UR3.

UR3 Robotic Arm – Integration

The Universal Robots UR3 is a 6-axis cobot with 3 kg payload and 500 mm reach. The arm handles 3D positioning while the BLE system independently manages gripper opening and closing.

• Payload: 3 kg  ·  Reach: 500 mm
• Axes: 6 DOF
• Gripper mount: 3D-printed ISO 9283 adapter
• Gripper control: Wireless BLE, independent from arm controller

Tentacle CAD Design – Autodesk Inventor + TPU

The tentacle was modeled in Autodesk Inventor with 12 identical vertebrae linked by flexible hinges. After 12 print iterations the optimal parameters were found. The tapered profile replicates real cephalopod arm geometry and distributes stress evenly along the full length.

CAD design in Autodesk Inventor — TPU 95A tentacle, 12 vertebrae, central Dyneema channel.

Flex Sensor Glove – Electronics

My PCBs – Glove & Gripper Boards

Two custom boards designed in Fusion 360 Electronics and milled on a Roland MDX-50. Each hosts a microcontroller and communicates via BLE, no shared wiring between glove and gripper.

GLOVE BOARD — TX  JP1–JP3 flex connectors · 6× SMD resistors

GRIPPER BOARD — RX  SERVO1 · SERVO2 · SERVO3 · LED indicator

Interactive System Nodes

Click each node to see detailed information about that subsystem.

BLE Packet Visualizer

Every 50 milliseconds, the glove reads the three flex sensors and packs the angles into a single text string, for example "30,60,90". Move the sliders to simulate bending your fingers.

Firmware – BLE Transmitter (Glove)

// BLE Transmitter — Wearable Glove
// XIAO ESP32-C6 | Fab Academy W15
#include <BLEDevice.h>
#define SERVICE_UUID "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHAR_UUID    "beb5483e-36e1-4688-b7f5-ea07361b26a8"
#define FLEX1 A0
#define FLEX2 A1
#define FLEX3 A2
BLECharacteristic *pChar;

void setup() {
  BLEDevice::init("OctopusGlove");
  BLEServer *srv = BLEDevice::createServer();
  BLEService *svc = srv->createService(SERVICE_UUID);
  pChar = svc->createCharacteristic(
    CHAR_UUID, BLECharacteristic::PROPERTY_NOTIFY);
  svc->start(); BLEDevice::startAdvertising();
}

void loop() {
  int a1 = map(analogRead(FLEX1), 0, 4095, 0, 120);
  int a2 = map(analogRead(FLEX2), 0, 4095, 0, 120);
  int a3 = map(analogRead(FLEX3), 0, 4095, 0, 120);
  String pkt = String(a1)+","+String(a2)+","+String(a3);
  pChar->setValue(pkt.c_str()); pChar->notify();
  delay(50);
}

Firmware – BLE Receiver (Gripper)

// BLE Receiver — Gripper Controller
// XIAO ESP32-C6 | Fab Academy W15
#include <BLEDevice.h>
#include <ESP32Servo.h>
Servo s1, s2, s3;
int angles[3] = {0,0,0};

class CB: public BLECharacteristicCallbacks {
  void onWrite(BLECharacteristic *p) {
    String v = p->getValue().c_str();
    int i1=v.indexOf(','), i2=v.indexOf(',',i1+1);
    angles[0]=v.substring(0,i1).toInt();
    angles[1]=v.substring(i1+1,i2).toInt();
    angles[2]=v.substring(i2+1).toInt();
  }
};

void setup() {
  s1.attach(3); s2.attach(4); s3.attach(5);
  BLEDevice::init("");
}

void loop() {
  s1.write(angles[0]);
  s2.write(angles[1]);
  s3.write(angles[2]);
  delay(20);
}

Communication Protocols

Packaging and Finished Product

The Octopus Gripper is designed as a self-contained, modular end-effector. Every component fits within a compact form factor that mounts directly to the UR3 flange and operates independently over BLE.

Project Timeline – Gantt

Link to Final Project

The system integration documented in this week is part of the complete Octopus Gripper final project. Full documentation including CAD files, firmware, assembly guide, bill of materials, and video demonstration is on the final project page.