Magnetic Stimuli Responsive Soft Robotic Display System Enabled by Quantum Dot Light Emitting Diode

Soft robotics are widely being researched and demonstrated in many fields of studies due to their unique compliant characteristics which can be delicately controlled through various driving forces. In particular, magnetic field actuation is found to be of significant importance due to its non-toxic, non-destructive, penetrative and contactless features. Here, we report magnetically responsive soft robotic system integrated with alternating current driven flexible quantum dot light emitting diode (QLED) for locomotive and deformable display under magnetic stimuli. The magnetic soft robotic display system demonstrates an interconnected characteristics of interactive display and locomotion through its magnetization profile, consisting of two main components: 1) Magnetized robotic body embedded with hard, ferromagnetic Neodymium-Iron-Boron micropowder in a compliant silicone elastomer matrix with silver nanowire embedded on top side for electrical conductivity, 2) Alternating current-driven quantum dot light emitting diode (AC-QLED) based on parallel in-plane electrode with separated gap, made flexible by using thin compliant substrate. Each component was carefully assembled with elastomeric spacer in between. The soft robotic display system demonstrates magnetically interactive electroluminescent locomotion capabilities, resulting from the interdependent interaction between both soft robotic module and flexible electroluminescent module.
The hard ferromagnetic Neodymium-Iron-Boron (NdFeB) powder, with diameter of ~5μm, was mixed with PDMS elastomer to form responsive body. After adding the curing agent into the prepared mixture, the mixture was poured onto another PDMS buffer layer embedded with conductive silver nanowire (AgNW) and cast with heat treatment. The cured magnetic elastomer body was tailored to desired dimensions. The cured conductive soft robot body was then wrapped around a glass rod and magnetized using vibrating sample magnetometer (VSM). The resulting magnetic soft robot showed transitional worm-like movement dependent on magnetic stimuli, such as the intensity of magnetic field and direction of magnetic field, while maintaining electrical conductivity on its surface due to embedded AgNW conductive layer.
Alternating current-driven quantum dot light emitting diode was fabricated to serve as the interactive display component. A parallel in-plane electrode with a gap of 100μm was prepared by sputtering ITO onto a 50μm thick Polyethylene Naphthalate (PEN) substrate. After cleaning the substrate with acetone and IPA, electron injection/transport layer, emissive layer, hole transport/injection layer and insulating layer were sequentially spin-coated under an N₂ atmosphere with heat treatment after each layer deposition. Finished AC-QLED was integrated with magnetic soft robot and spacer through pre-polymer glueing and connected to power supply.
The magnetic soft robotic body exhibited worm-like deformation according to the orientation of external magnetic field, leading to contact with AC-QLED display unit. The contact area where luminescence was displayed through the induced electrical field, was proportional to the degree of deformation under magnetic field, resulting in successful visualization of magnetic intensity/orientation and locomotion through magnetic input. Our magnetic soft robotic display system does not only provides sensing information regarding magnetic stimuli but also enables locomotion of the entire sensing system. Its magnetically interactive electroluminescent locomotion without complex electrical interconnection or fluidic apparatus makes it suitable for dynamic environmental navigation and mapping visual guidance. Moreover, the bending deformation of display unit enabled by magnetically responsive soft robotic body can also be applied to haptic feedback display applications, providing tactile and visual feedback simultaneously upon magnetic stimuli.