InflatiBits - A Modular Soft Robotic Construction Toy

InflatiBits is a modular construction toy that enables playful construction and exploration of pneumatically actuated kinematic systems. The set contains different building blocks based on soft robotics principles such as soft inflatable air-chambers, constraining elements, air-connectors, pressure sources, and sensor modules. The elements can be combined and actuated manually or through an optional Arduino-based control board. The board contains a motorized air-pump, solenoid valves and allows for connecting the sensor module to achieve more complex behaviors and motion patterns. The InflatiBits modules and connectors are compatible with standard Lego parts, enabling children to integrate them into existing playing environments.

Christopher Kopic & Kristian Gohlke

Bauhaus-Universität Weimar, Germany / April 2015 /


Design and Fabrication

01 - Design

The goal of InflatiBits is to provide quick, easy and fun tools for building your own soft robotic structures with minimal effort. To reach this goal we split standard soft actuator designs into their core components, that serve as building blocks which can be freely combined to create a wide range of soft actuators.

InflatiBits Modules

Below is an overview of the basic building blocks:


InflatiBits Extenders

Extenders are fabricated from soft silicone with an internal zero volume air chamber. and air-inlets/outlets at the top and at the bottom. They extend in one direction, when inflated. The footprint of the extenders is compatible with the Lego grid.

Air Connectors

InflatiBits Air Connectors

Networks, stacks and arrays of Extenders are interconnected through Air Connectors such as flexible and rigid tubes, y-connectors and plugs. Syringe pumps can be used to manually control the system pressure.

Rigid Restrictors

Rigid Restrictor

Rigid Restrictors can be used to create mechanical connections between the Extender modules to modify their linear expansion behavior. They attach to the grommets surrounding the Extenders and cannot be stretched or bent.  

Bending Restrictors

Bending Restrictor

Bending Restrictors can be made from air Tubes and two end caps. They can't be stretched, but are bendable and also attach to the side grommets of the extender chains.

Sliding Restrictors

Sliding Restrictor

Sliding Restricors allow for controlled extension of the Extender up to a certain length. This special type of restrictor is made from a flexible plastic stick with a fixed mechanical connector at each end, and one or several sliding elements in between.

02 - Fabrication

Extender Construction

Extenders consist of two identical halves made of silicone rubber that are joined together to form the final module. The silicone for each halve is poured into its individual two part mold (with inserted rods to achieve clean holes). Both halves are then glued together at the end of the curing process with the same silicone.

Air connectors, as well as all rigid restrictors can be machined on a turning lathe from acrylic rods.

Bending Restrictors consist of a piece of tube and two end caps made from machined acrylic rods or 3D printed parts or a combination of both.

Sliding Restrictors consist of 3D printed caps connected by plastic filament.

For Details on the materials used, see the Bill of Materials.

Bill of Materials

Mechanical Parts

- Smooth-On Dragon Skin 10 Silicone

- Acrylic rods, Ø 6mm, round (for rigid and air connectors)

- flexible polyamide filament, Ø 2mm (for flexible connectors)

- PVC tubes,  Ø 6mm 

- standard ABS filament for 3D-Printing

- ..add Lego bricks as needed


- Atmega ATtiny 85

- Arduino Leonardo

- Airpump and Solenoid valves (scavaged from Sanitas SBC 21 portable blood pressure monitor

- MPX5500DP Pressure Sensor (


Provided are:

A construction manual for the set.

A summary of the main ideas that lead to designing this toy.

Technical drawings for all parts

IGES and STL models of the Extender mold


inflatibits_concept.pdf427 KB
inflatibits_manual.pdf666 KB
inflatibits_extender_mold.zip285 KB
inflatibits_technical_drawings_.pdf190 KB

Case Studies: User Exploration & Example Constructions

Example Constructions

We contructed different types of grippers and simple walking devices to explore their capabilities and test the feasibility of more complex constructions. An selection of examples is shown below.

InflatiBits Example Builds

User Explorations

InflatiBits Case Studies

We conducted a series of informal user explorations with children between 5 and 15 years of age. The InflatiBits was also presented publicly at two events, the Summæry  2015 the annual exhibition of the Bauhaus-Universität Weimar and the Demo Session of theTEI 2016 conference. 

At both events the construction set was presented as a as a walk-up-and-use hands-on exhibit. Visitors could visitors could freely interact with the modules, and user behavior, comments, interaction time and reactions to the system where observed. 

Control System & SensorBlocks

A seperate control system consiting of an Arduino microcontroller and solenoid valves as well as air-pumps scavaged from blood-pressure monitoring devices (see BOM) can be used for dynamic and interactive control of InflatiBits creations. The set currently consists of a pressure-generator block and different sensor blocks. That can be connected to dynamically interact with the pressure of one or several air-chamber networks.

The pressure block contains an Arduino Microcontroller, an electronic membrane-pump, solenoid valves and a pressure sensors. All sensor blocks contain ATtiny Microcontrollers and a specific sensor, such as light, piezo-knock sensors or force-sensing resistors. The blocks communicate via the i2c protocol.

InflatiBits SensorBlocks

Work in Progress and Outlook

Based on the insights from the first InflatiBits prototypes, we are currently in the development to simplify both, the fabrication of modules and extend their capabilities as a construction toy.

  • We are adding new structural elements for orienting your built tentacles in 3d space. This eliminates the need, but not the possibility, of using Lego in your creations.
  • Air pockets made from weldable fabrics. While silicone is commonly used in soft actuators, it is not well suited for toys. Due to its cost, tearability and complex time consuming manufacturing process. Initial experiments with weldable fabrics as a means to create low-profile and robust zero volume air-pockets have shown to deliver promising results.
  • Integrated electronic control and sensing. In the first iteration  prototype of our system, the electronic control blocks were treated as an optional add-on and rarely used by testers. We are currently developing a system that is much more integrated into the modules and focuses on achieving organic motions rather than building conventional robot like sensor-actuator systems.


Corresponding Author