Hero Arm – User Guide

Raimi picks up tile, wearing Iron Man Hero Arm Cover

Hero Arm - Overview

The Hero Arm is a powered bionic limb controlled by your muscles, with intuitive lifelike precision. Each Hero Arm is bespoke, perfectly formed just for you, with a breathable removable socket for enhanced ventilation and ease of cleaning. Powered by high-performance motors, advanced software and long-lasting batteries, it is lightweight and stylish. This page will give you an overview of how to use and look after your Hero Arm, and the important safety considerations to take.


The hand comes in three sizes, and at 280g - 346g (0.62lbs - 0.76lbs), is the lightest bionic hand. The full arm weighs less than 1kg (2.2lbs)


Haptic vibrations and beepers on the electrodes, as well as buttons and lights provide you with intuitive notifications


EMG muscle sensors within the Hero Arm detect muscle movements, and give you proportional control

Handala Red

Multiple grips

Upto six easy-to-select grips, such as fist, hook, pinch and tripod, giving you outstanding versatility and control

Stylish covers

You can choose from a range of swappable covers; Star Wars BB-8, Marvel Iron Man, Disney Frozen and coming soon: Alita Battle Angel

dynamic socket

An adjustable socket and a removable ventilated liner (both custom 3D-printed) give you exceptional fit and comfort


Each Hero Arm is custom built for every individual, and comes in 3 different hand sizes and 2 different arm layouts. As a result, you may see some differences between your Hero Arm and the diagrams in this manual. The Hero Arm comes with either a 3 Motor or 4 Motor Hand depending on the most suitable size of hand for your arm. The key differences are the reduced size of the 3 Motor version, and the number of tendons. The 4 Motor versions have 2 tendons on both the index & middle fingers, which allows them to move independently. On the 3 Motor version, the index & middle fingers will always move together.

4 Motor Hand

3 Motor Hand


Every socket is designed and 3D printed for each individual based on a 3D scan of their arm, and comes in two different layouts: internal or external battery. The functionality of both layouts is exactly the same, but they have some noticeable cosmetic differences as shown below:

Internal Battery Style Hero Arm

External Battery Style Hero Arm

Getting Started

Before putting on your Hero Arm for the first time, please familiarise yourself with  this user manual. 

When to Use your Hero Arm

The Hero Arm is intended to be used for day to day activities that require the use of  one or two hands. It is intended to be used for light to moderate activities such as:  

● Holding objects such as cups, tools, kitchen utensils, trays, bottles, bags
● Performing operations such as opening doors, pressing buttons, getting  dressed 

The Hero Arm is not intended for use in activities that may result in injury or death to  the user or others as a result of it failing to perform the activity as intended. As such,  activities which are specifically prohibited include:

● Driving any form of motor vehicle, aircraft or boat, 
● the use of firearms, or 
● use while partaking in contact sports, watersports or extreme sports.  

For all other activities, you should assess the impact of the following: 
● The Hero Arm suddenly ceasing to function (for example if it were to run out  of battery). Bear in mind that this could leave the device unable to release.  
● The Hero Arm losing its grip.  
● The Hero Arm moving unintentionally. 
● The Hero Arm shifting position on, or coming off your arm.   

If the consequence of using the Hero Arm for any of the above activities is injury or  death to yourself or anyone else, the Hero Arm must not be used. In the case of  using the Hero Arm to return to work, you should discuss the above points with your  Health and Safety representative and conduct a formal risk assessment.   

You can use your Hero arm above -5 °C (23 °F) and below +50 °C (122 °F). You can  use it at pressures equivalent to altitudes of up to 4000 m (16,400 ft), making it safe  to use in the cabin of a commercial airliner. Your Hero arm is IP20 rated, meaning it  is not waterproof. You should avoid exposing it to any water. If your Hero Arm does  get wet, turn it off, remove the battery and leave it to dry fully. 

Putting on your Hero Arm

Your Hero Arm has been designed to perfectly fit your arm, and comes with an adjustable BOA Fit System™ to reach the perfect balance of comfort and secure fit.

You can easily adjust the fit of your Hero Arm throughout the day without removing it, simply by adjusting the BOA Dial.

Dan puts limb into Deus Ex Hero Arm
Dan putting on his external battery Hero Arm

Switching on

To switch on your Hero Arm, press the Hand Button for 1 second. The Hand Button will pulse purple while initialising. Once the arm is on and ready to use, the Hand Button pulses white. The multi-function button on the back of the hand can be used to control a variety of functions of your Hero Arm:

Hand On/Off

To switch on your Hero Arm, press the button for 1 second. To switch off your Hero Arm, press the button for 3 seconds

Check Battery Status

To check the status of the battery, with your Hero Arm switched on, hold the Hand Button down for 1 second. 

Change Grip Group

Your Hero Arm has multiple grip groups, to change between these, press the Hand Button for 0.5s. See ‘Grip Modes’ for more info.


Your Hero Arm comes with a battery and Smart Charger. The battery life of your arm will vary depending on how heavily you use it, but we recommend charging it every night. You must remove the battery from the arm before charging. For safety reasons, only ever charge your battery using the Smart Charger provided with your arm. Follow the steps below to charge your Hero Arm battery: 
  1. Switch off your arm by holding down the Hand Button for 3 seconds
  2. Once switched off, remove the battery cover and unplug the battery, by pressing the latch and pulling on the white connector
  3. Remove the battery from the arm by gently pulling on it
  4. Plug the battery into the supplied Smart Charger
  5. Plug the charger into a mains power outlet
  6. The status Hand Button of the Smart Charger will flash to indicate that the battery is charging
  7. When the battery is fully charged, the status Hand Button will stop flashing
  8. You can now disconnect the battery from the Smart Charger and reconnect it to your Hero Arm

Checking the battery status

Hand Button Colour

Battery Level

40% – 100%

20% – 39%

2% – 19%

Under 2%

Notifications / Status

The Hero Arm will notify you of a variety of status changes through the Hand Button colour, vibration, and beeper. These are summarised below (in addition to the battery level indicators listed in ‘Checking the Battery Status’

Controlling your bionic hand

The Hero Arm comes with an advanced myoelectric, multigrip bionic hand. The EMG Sensors in the arm detect your muscle movements, and the hand responds for intuitive control. When being fitted for your Hero Arm, your prosthetist will have found the optimal location of the EMG Sensors for your muscles.

The bionic hand is controlled by tensing the same muscles which are used to open and close a biological hand. To close the Hero Arm’s hand, and perform the selected grip, imagine flexing the wrist inwards while pulling the fingers into the heel of the hand. To open the hand, imagine extending the wrist with an outstretched palm.

The hand will move more slowly when your muscles are tensed gently, and will move more quickly with a firmer tense. This control can be useful for manipulating small or delicate objects.

Grip Modes & Changing Grips

The Hero Hand has 4 different grip patterns in the 3 motor version, and 6 different grips in the 4 motor version. These grips are grouped together in pairs to make switching between them quick and easy. To switch between grips within a group, move the hand into the open position, relax, then hold an open signal for more than a second.

You will feel a long vibration, and the Hand Button will flash green a number of times to indicate which grip number you have selected; 1 flash for the 1st grip in the group, and 2 flashes for the 2nd grip in the group. To switch between the different groups, press and release the Hand Button. You will feel a short vibration, and the Hand Button will flash purple a number of times to indicate which group number you have selected – i.e. 1 flash for group 1, 2 flashes for group 2.

Group 1 – Fist and Hook

The primary group contains the Fist and Hook grips:


This grip is useful for carrying round objects such as bottles or fruit, for holding utensils and handles, and can also be used for handshakes. First, the thumb closes, followed by all 4 fingers.


Similar to the Fist grip, however the thumb remains open while the four fingers close. This is ideal for carrying a shopping bag or briefcase, and also allows you to do a “thumbs up” gesture.

Group 2 – Tripod

The secondary group contains two Tripod Grips. These are useful for picking up and manipulating small objects, such as car keys, coins, jar lids, pens etc.

Tripod A

The middle and index fingers close to meet the thumb. The ring and little fingers remain open.

Tripod B

The ring and little fingers close when selecting this grip, and when sending the close signal, the index and middle fingers then close to meet the thumb. You can make a “peace” hand signal with this grip.

Group 3 – Pinch

The final group, only available on the 4 Motor versions of the hand, contains two Pinch Grips. The Pinch Grips are useful for manipulating small objects or picking things up off a table such as a coin or pen. The pinch grips work with the thumb knuckle in both the closed and open positions – if you’re finding it difficult to pick up a small object, try moving the thumb knuckle.

Pinch A

The index finger closes to meet the thumb, all other fingers remain open. You can make an “A-OK” hand sign with this grip.

Pinch B

When selecting this grip, the middle, ring and little fingers will close, and when sending the close signal the index finger will then close to meet the thumb. You can use this grip to point, or do a “come here” gesture.

Cameron Millar writing with Star Wars BB-8 Hero Arm Covers
Cameron using tripod grip on a 3-motor hand to hold a pencil

Freeze Mode

Freeze Mode can be used with any of the grip patterns to temporarily freeze the position of the hand and disable the muscle control – this allows you to set a grip position without worrying about accidentally sending a muscle signal and releasing your grip. To activate Freeze Mode, hold down the Hand Button for 1 second whilst tensing the ‘Close’ muscles – the Hand Button will change to light blue (aqua) and there will be a vibration to indicate Freeze Mode has been activated. Freeze Mode will remain active until you disable it by pressing the Hand Button.

Wrist Rotation

You can adjust the rotation of the wrist through 180°. To do this, depress the Wrist Button at the base of the wrist (on the back of the hand), and rotate to the desired angle. Release the button to lock the wrist in the new position.

Thumb Flexion

In addition to the powered movement of the thumb, the knuckle can also be manually adjusted into either the open, middle or closed position.





Fully closing the thumb makes it easier to pull the Hero Arm through the sleeves of clothing. The middle thumb position can be useful for picking up small objects:


When you power on your Hero Arm for the very first time, the hand may perform a calibration routine – this will involve closing each of the fingers and the thumb in order to check everything is working correctly. It is important that the fingers are not obstructed during calibration, as this could cause the calibration to fail. The Hand Button will pulse purple to indicate the hand is calibrating. A successful calibration is indicated by the Hand Button turning white once the movement of the hand has stopped.


If the calibration is unsuccessful for some reason, such as an obstruction preventing the full movement of any of the fingers, the hand will repeat the calibration a second time – ensure any obstruction is cleared before the process repeats. If any finger fails calibration, it will remain in the open position and will not respond to muscle inputs.


If you disconnect the battery before powering off the hand, it will need to recalibrate the next time you power it on. You should therefore always switch off your hand, if it is working correctly, by holding down the Hand Button, before disconnecting the battery.


There may be some situations when you want to force the hand to calibrate, such as if a finger is no longer closing or opening fully – in this scenario it is then acceptable to disconnect the battery with the hand powered on in order to initiate a calibration.


Your Hero Arm can be customised with swappable covers, to match your style or mood. There are 3 types of cover: hand cover; arm covers (split into two halves) and battery cover. Each cover is custom designed to fit your Hero Arm perfectly. To attach the hand cover, position the cover over the back of the hand, lining up the opening for the Hand Button, and press gently – the cover will snap into place. To remove, pull gently from one side of the cover to flex it off the hand.


Depending on whether you have an internal or external battery style Hero Arm, your covers will look slightly different. To attach the battery and arm covers, line up the fastening pads on your cover with those on your arm, and press the cover firmly into place – you should hear a click when the fastening pads have engaged. To remove the cover, gently pull it free from your arm. To ensure your battery is protected, you must wear the battery cover at all times if not wearing any other arm covers. For more cover options, and to design your own, go to the Open Bionics shop.


Internal Battery Style Hero Arm

External Battery Style Hero Arm

Looking after your Hero Arm, and yourself

Although the Hero Arm has been engineered to be strong and robust, you should treat it as if it were your own limb – please read this section of the manual for general safety information and guidance on how to care for your arm. Avoid subjecting your arm to excessive loads or impacts – your safety should not rely on the arm at any time.


You must always have at least the battery cover on your arm. You should not attempt to lift or carry objects heavier than 8kg (17.6lbs). If you have a particular activity or sport that you want to play whilst wearing your Hero Arm which might subject it to excessive impacts or force, we would recommend first discussing this with your prosthetist.


Your Hero Arm can withstand splashes of water (such as light rain), however it is not water resistant. Do not submerge your Hero Arm in water – it should be protected from moisture at all times. If any water reaches the internal components of the hand or arm they are likely to cause damage and eventual failure. Water damage is not covered by the standard 12 month warranty.


Do not expose it to a naked flame or subject it to excessive heat. If the hand temperature reaches 50°C / 122°F, the hand will warn you by flashing the Hand Button yellow and blue. At 55°C / 131°F, the Hand Button will flash yellow and red, and you will be notified with a beep before the hand shuts itself off.

Hazardous Activities

The Hero Arm is not intended for use in activities that are hazardous and may result in injury to the user or others as a result of failure to perform the activity as intended. Activities which are prohibited include, but are not limited to the following:

  • Driving of motor vehicles, aircraft or boats
  • Operating power tools or heavy machinery
  • Use of firearms
  • Professional use by military, medical  or emergency service personnel
  • Use while partaking in contact sports, watersports  or extreme sports


Storage & Maintenance

When not using your Hero Arm, you should store it carefully, between -5°C and 30°C (23°F and 86°F), out of direct sunlight. We recommend you do not attempt any maintenance or modification of your Hero Arm by yourself. If your arm is not functioning as you think it should, or has been damaged, you should contact your prosthetist to arrange for repair or replacement.


The Hero Arm can be cleaned using antibacterial wipes. In addition, the flexible internal socket is easily removable from the frame of your Hero Arm to make cleaning easy. You should clean the flexible socket using warm, soapy water on a regular basis. The steps below apply to both Internal & External Battery style Hero Arms.

Growing out of your Hero Arm

If you are still growing, your Hero Arm may eventually become too small. While the BOA Fit SystemTM allows you to adjust the tightness of your socket, the length is not adjustable. This means that when your arm grows in length, the EMG muscle sensors may no longer be in the correct position relative to your muscle sites, and your Hero Arm may struggle to detect when you send an open or close signal. You may also find that it becomes difficult to put your Hero Arm on. If you think that you have outgrown your Hero Arm, speak to your prosthetist who can advise you about a re-fit. You can get your Hero Arm resized for substantially less than the cost of buying a whole new unit.


If you experience any issues with your Hero Arm, please try the following solutions. If you are unable to solve the problem, please contact your prosthetic provider, or Open Bionics at support@openbionics.com



Fingers are not moving/responding to my signals

Check to make sure the Hand Button is pulsing white to show the hand is on and ready


Press gently on the back of the EMG sensors, to make a better skin contact


Check the battery is fully charged and plugged in correctly

Fingers are not closing/opening fully

Try calibrating the the Hero Arm by disconnecting the battery with the power still ON (see the Calibration section)

There is a loose tendon attached to one of the fingers

A tendon has become damaged from excessive wear or load, please discuss with your prosthetist to arrange for your Hero Arm to be repaired

One finger stays open whilst the other fingers/thumb move normally

The finger that remains open has likely failed calibration. Try calibrating the Hero Arm by disconnecting the battery with the power still ON (see the Calibration section). If this issue continues, contact your prosthetist

The button is not responding to presses but the arm is on

Try disconnecting and reconnecting the battery

The grip patterns are not performing normally

Try calibrating the the Hero Arm by disconnecting the battery with the power still ON (see the Calibration section)

Fingers are moving erratically

Try cleaning the EMG pads with an alcohol wipe, remove and reattach your Hero Arm

Fingers are responding intermittently to signals

Try cleaning the EMG pads with an alcohol wipe, remove and reattach your Hero Arm

Hand Button is flashing different colours

Please see the table in ‘Notification Statusfor information on what the Hand Button colours mean

The Hero Arm has got wet

Immediately disconnect and remove the battery. Dry off any visible water. Leave the hand to dry completely before trying to switch on again


Your Hero Arm comes with a Li-Ion 7.5V 2600mAh battery. Only use the battery issued with your Hero Arm, or another purchased from the Open Bionics store. Only charge the battery according to the guidance provided in the ‘Charging the Battery’ section of this page, using the provided charger. Do not expose the battery to water, or leave it in an extremely hot environment such as in a hot car, or exposed to direct sunlight.Battery performance is dependent on how you use the arm, but also on the environment – battery performance may decrease in cold temperatures. 

How to store the battery

If you are not planning on using your Hero Arm or its battery for a long period of time, we recommend you fully charge the battery before storing it in a cool dry place. To maintain the battery’s function, you should fully run down and recharge the battery at least once a year. 

Battery life

Batteries have a limited life, and will lose capacity over time the more they are used. If your battery life seems significantly shorter than it used to, you may need to purchase a new one.


The symbol on the battery indicates that it is not to be treated as household waste. By disposing of the battery correctly, you’ll be helping minimise any negative consequences for the environment. Please contact your local authority for information on where you can recycle the battery.


Please follow these guidelines in regards to the battery for your Hero Arm

  • Do not bend or crush the battery
  • Do no pierce the battery
  • Do not try and disassemble the battery in any way
  • Do not expose to excessive heat or leave in a vehicle
  • Do not leave in direct sunlight
  • Do not attempt to modify the connector or wiring of the battery in any way
  • Do not use a damaged charger with the battery
  • Do not use any charger other than the one provided
  • Do not attempt to use the battery with any device other than your Hero Arm
  • Do not dispose of the battery in regular waste – you must recycle it

If you observe any leaking from your battery, or it has swollen in any way, you must:
  • Immediately disconnect it from the Hero Arm or Smart Charger
  • Move the battery to a safe place and keep a minimum distance for 30 minutes
  • Do not attempt to reuse the battery – you must dispose of it
  • Contact your prosthetist to inform them of the situation

Warranty & Returns

The Hero Arm, its battery and Smart Charger are covered by a standard 12 month warranty. This guarantees against any manufacturing defects or defects with your Hero Arm which arise out of normal use. You can purchase additional warranty packages to extend the length of cover – please discuss this with your prosthetic provider.

If you think there is a problem with your Hero Arm, please first carefully read through this manual in case any of your issues are addressed, before contacting support@openbionics.com or your prosthetic provider. The warranty does not apply to any components that have been subject to misuse, excessive loads, subject to water damage, deliberate damage or modification by uncertified persons unless otherwise permitted in this user manual or given written permission from Open Bionics Ltd.

Please quote the serial number for your Hero Arm when requesting any warranty repairs or returns. This can be found on the product information sticker located under the battery on your arm. When returning your Hero Arm to us, please ensure you package it appropriately – the original packaging you received your arm in is great for this purpose.

Regulatory Compliance

Open Bionics declare that they meet appropriate European standards for design, manufacture and supply of prosthetic products. All individual products are marked indicating that they comply with the requirements of the Medical Devices Directive 93/42/EEC (MDD), as amended by Directive 2007/47/EC. The ce.png mark  may be applied on packaging, accompanying literature or an enclosure, rather than the product itself. The Hero Arm and its associated components listed in this document are covered by certificates for:

Applicable standards

Applicable EU Harmonised Legislation

EN 60601-1

EN 60601-1-2

EN 60601-1-6

Medical Devices Directive 2007/47/EC

Child sitting on bike wearing Iron Man bionic arm

Hero Arm User Guide – Version: 100583_01_0, updated February 2019