Machine-knitted fabrics that snap between multiple stable shapes have been developed using standard industrial weft knitting and highly elastic yarns, producing soft, stretchable textiles that function as switches and sensors. The technique uses a method called plating, which exposes different yarns on each face of the fabric, generating dense three-dimensional structures that curl and snap between configurations without polymer moulding or residual stress programming.
- Researchers combined horizontal and vertical stripes to build fabrics that settle into more than one stable configuration, mirroring the on-and-off function of a light switch.
- Fine conductive yarns embedded in the knits allow the fabric to function as a soft electric switch, with the snapping motion between stable shapes triggering a change in electrical state.
- A wearable textile switch, worn at a joint such as the knee or elbow, produces a snapping motion that an Arduino reads to count steps, demonstrating a practical wearable application.
- The findings have been published in 'Knitting Multistability' in Advanced Functional Materials by researchers at Harvard SEAS.
HOW IT WAS BUILT: The research has been led by Kausalya Mahadevan, a recent Ph.D. graduate and postdoctoral associate who began in the lab of Katia Bertoldi, the William and Ami Kuan Danoff Professor of Applied Mechanics at Harvard SEAS, as an undergraduate. The team has used weft knitting, the same industrial process used for hats and gloves, with highly elastic yarns and a plating technique, drawing on how textile artists approach structures alongside the lab's established work in nonlinear mechanics.
- The plating technique exposes different yarns on each face of the fabric, producing dense, thick textiles that naturally curl into three-dimensional shapes without polymer moulding or residual stress programming.
- The team has mapped how geometry and material choice affect snap-through behaviour by systematically combining horizontal and vertical stripes to identify the physical regimes in which knitted textiles become multistable.
- The research has been supported by NSF grant DMR-2011754 and ARO MURI programme W911NF-22-1-0219, with equipment support from ONR DURIP Award N00014-19-1-2220.
WHAT IT CAN DO: To demonstrate practical applications, the researchers have embedded fine conductive yarns into their knits, turning the fabrics into soft, stretchable electric switches that change state as the textile snaps back and forth. Three working prototypes have been produced and exhibited as part of a recent Art Lab installation, and the project edges textiles closer to the broader field of nonlinear mechanical metamaterials, where structures are engineered to bend, buckle and snap in useful ways.
- A multistable knitted shell shape turns an LED on and off as it flips between stable states, showing that a soft knitted structure can replace a rigid switch.
- When mounted over the knee or elbow, the textile switch creates a snapping motion that an Arduino can read to count steps.
- A reconfigurable lamp shade incorporates three separate multistable switches, each controlling a different colour of light as the fabric stretches and snaps between positions.
- Looking ahead, the team is exploring whether multistable control can produce textiles that are soft, seamless and functional, with potential uses in movement monitoring, tactile feedback and on-demand shape change.
WHAT THEY SAID
I've always been excited about fabrics and textiles, and what we can engineer and build with them. Our ideas around multistability in textiles arose from being inspired by textile artists and how they approach structures, combined with how [Bertoldi's] lab has traditionally thought about nonlinear mechanics in solids … the yarn selection and machine parameter choices allowed us to basically select a fabric that is going to be as snappy as we can possibly get.
— Kausalya Mahadevan
Postdoctoral Associate, Lab of Katia Bertoldi
Harvard SEAS
