ModiFiber: Two-Way Soft Thread Actuators for Tangible Interaction. Jack Forman, Taylor Tabb, Youngwook Do,  Mohan Yeh, Adrian Galvin, Lining Yao.

Thread Actuators In Motion

Thread Actuators In Motion

Scanning Electron Microscope Imagery Of Thread Actuators

Scanning Electron Microscope Imagery Of Thread Actuators

Despite thin-line actuators becoming widely adopted in different Human-Computer Interaction (HCI) contexts, including integration into fabrics, paper art, hinges, soft robotics, and human hair, accessible line-based actuators are very limited beyond shape memory alloy (SMA) wire and motor-driven passive tendons. In this paper, we introduce a novel, yet simple and accessible, line-based actuator. ModiFiber is a twisted-then-coiled nylon thread actuator with a silicone coating. This composite thread actuator exhibits unique two-way reversible shrinking or twisting behaviors triggered by heat or electrical current (i.e., Joule heating). ModiFiber is soft, flexible, safe to operate and easily woven or sewn, hence it has a great potential as an embedded line-based actuator for HCI purposes. In this paper, we explain the material mechanisms and manufacturing approaches, followed by some performance tests and application demonstrations.

ModiFiber has been accepted to the ACM CHI Conference on Human Factors in Computing Systems, and I will present the work in Glasgow, UK in May. Full text of text of the paper can be found in ACM’s Digital Library.

I contributed to a variety of aspects of this project, but primarily in design and build of the semi-automated machine, fabrication of application prototypes, and graphical/document design of the submitted paper.


ModiFiber as a twisting actuator. (B) Spinning tassels as fashion style piece. (C) Clothing that engages an origami structure for tunable porosity. (D) A non-invasive haptic feedback actuator that heats and squeezes the user as a notification reminder. (E) Smart packaging for a self-stirring tea bag. (F) The semi-automated machine used to fabricate such actuators.

Technical Details

Our work is motivated by the potential of adapting and improving fishing line actuators for HCI and to add ModiFiber to the library of string actuators commonly used in HCI. ModiFiber presents the following contributions:

  • A novel composite structure to achieve reversibility on top of existing nylon-thread actuators.

  • A proposal and quantification of two actuation types. From 1-ply ModiFiber actuators: shrinking actuation and twisting actuation. From 2-ply ModiFiber actuators, shrinking actuation in which the shrinking is inherently restricted only to linear movement.

  • Use cases for the two actuation types, and summarization of the design space including applications in performative garments, fashion, interactivity, and packaging.


We designed a semi-automated machine implementing a two-phase process of coiling and collecting, which we have used to obtain working lengths of approximately 2-3 meters.


We embedded the ModiFiber shrinking actuator into the sleeves of a shirt for on-body haptic feedback. The sleeve can react to a variety of conditions- ranging from text message notification to barometric pressure drops to activate the garment. When triggered, the actuator begins to warm and constrict around the user’s arm. Once deactivated, the actuator relaxes and the shirt loosens.


The first garment has spinning tassels as style piecThe second garment engages an origami structure allowing the porosity of the garment to be tuned (Figure 13). This garment uses a 57.75 cm long shrinking 2-ply thick actuator that is annealed with 1.2 kg at a .60A current and coated in Dragon Skin 30A. The garment is powered by two 9 volt Li-ion This is achieved by using six twisting thin actuators, coated with MoldStar 20T. Each tassel is powered by a single 9 volt NiMH battery (6 total).

ModiFiber thread actuators can provide two reversible actuation types: shrinking actuation and twisting actuation.


ModiFiber structure: (A) depicts a twisted nylon thread with (B) a silver coating. The coiled muscle is then coated in silicone C. (D) depicts the elongated polymer chains before heating and (E) depicts the contracted polymer chains after heating


We implemented actuators into two garments to demonstrate the potential for these applications in transformative fashion. The actuators are well-suited to these applications, as external restorative forces, like weights or a spring, are not feasible for wearables.

The first garment has spinning tassels as style pieces. This is achieved by using six twisting thin actuators, coated with MoldStar 20T. Each tassel is powered by a single 9 volt NiMH battery (6 total).