Jae-Hyun Kim | KIMM: How do you roll-transfer thousands of microLEDs onto a custom metamaterial PCB at scale?
00:05:50.200 - 00:08:23.600
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How do you roll-transfer thousands of microLEDs onto a custom metamaterial PCB at scale?
The manufacturing of meta-displays requires a complex integration of fluidic or mechanical transfer, precise patterning, and structural release. First, microLEDs are distributed on a temporary soft carrier substrate known as an interposer, while a specialized meta-printed circuit board (meta-PCB) is fabricated with corresponding contact pads. The assembly is then processed using high-speed roll-based mass transfer technology to selectively pick up and place the microLEDs.
To achieve robust electrical and mechanical connections, eutectic bonding materials are pre-patterned between the microLED contact pads and the meta-PCB electrodes. The application of localized thermal energy initiates the eutectic reflow, forming reliable metallurgical joints capable of withstanding subsequent mechanical stress. Following successful transfer, an ultraviolet (UV) laser cutting system is deployed to carve precise cutting lines into the substrate, isolating the meta-atoms and enabling the intended auxetic mechanical movement.
This process achieves high throughput, demonstrated here with a roll-based transport speed reaching 21,000 devices per minute. This high-efficiency mass transfer is proven on 4-inch scale green panels with a resolution of 50 PPI, successfully manipulating ultra-small microLEDs measuring only 28 microns by 48 microns.
In this short video, you can learn:
* The step-by-step manufacturing flow of stretchable meta-displays from interposer to final substrate
* How roll-based mass transfer and eutectic bonding enable reliable assembly at speeds of 21,000 devices per minute
* The post-transfer UV laser cutting process used to structurally isolate meta-atoms for mechanical flexibility
š **Clip Abstract** This clip details the manufacturing flow of stretchable meta-displays using high-speed roll-based transport and eutectic bonding. It demonstrates the precise assembly of 28x48 micron microLEDs onto a meta-PCB followed by laser-based mechanical release.
#RollBasedMassTransfer, #EutecticBonding, #AuxeticMetamaterials, #UVLaserSingulation, #MicroLEDDisplays, #StretchableElectronics
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00:01:43.100 - 00:04:16.200
How can we stretch a microLED display without distorting the displayed image?
How can we stretch a microLED display without distorting the displayed image?
Conventional stretchable displays suffer from image distortion during deformation due to the positive Poisson's ratio of standard elastomeric substrates. When these substrates are stretched uniaxially, they compress in the perpendicular direction, squeezing and warping the pixel pitch. To overcome this limitation, researchers are leveraging auxetic metamaterials engineered to exhibit a negative Poisson's ratio, ideally reaching a value of minus one.
This negative Poisson's ratio means that when the display is stretched along one axis, it simultaneously expands along the perpendicular axis, maintaining the proportional spatial distribution of the microLED pixels. The auxetic behavior is physically realized through a meticulously engineered network of rotating rigid micro-plates (scales) connected by flexible hinges. This structural configuration ensures that the relative coordinates of the active light-emitting elements expand uniformly, preventing any geometric distortion of the projected image.
The layout of these meta-atoms integrates positive and negative electrodes alongside precise laser cutting lines to enable mechanical decoupling. Finite element analysis (FEA) is utilized to optimize these structures, showing that incorporating specific circular strain-relief hole arrays into the hinge designs can significantly increase the stretchability threshold by an additional ten percentage points.
In this short video, you can learn:
* The critical role of Poisson's ratio in preventing image distortion in stretchable displays
* How auxetic metamaterials achieve a negative Poisson's ratio of minus one
* The mechanical design of rotating rigid scales and strain-relief hinges for uniform 2D expansion
š **Clip Abstract** This clip explains how auxetic metamaterials with a negative Poisson's ratio are used to eliminate image distortion in stretchable displays. By utilizing rotating rigid scales and flexible hinges, the display expands uniformly in both axes when stretched, maintaining perfect image proportions.
#AuxeticMetamaterials, #NegativePoissonsRatio, #StretchableMicroLEDs, #StrainReliefHinges, #FlexibleElectronics, #MicroLEDDisplays
00:08:27.700 - 00:11:02.100
Why do conventional flexible displays crumble on spherical surfaces while meta-displays conform perfectly?
Why do conventional flexible displays crumble on spherical surfaces while meta-displays conform perfectly?
Standard flexible displays utilizing polydimethylsiloxane (PDMS) substrates are constrained by a positive Poisson's ratio of approximately 0.5. Under uniaxial stretching, this high positive value induces severe perpendicular compression, resulting in structural buckling, wrinkling, and localized pixel crowding. Conversely, the auxetic meta-display maintains a measured Poisson's ratio of minus one, matching lateral expansion to longitudinal stretch to yield perfectly isotropic deformation.
This isotropic expansion property is crucial for conforming displays to complex 3D non-coplanar geometries, such as spherical and bi-axial surfaces. When attempting to wrap a conventional flexible microLED panel onto a sphere, the excess material inevitably crumbles and folds due to the lack of local stretchability. In contrast, the engineered meta-display stretches uniformly, accommodating the double curvature of a sphere without mechanical failure or image distortion.
Experimental demonstrations highlight the viability of this approach on spherical surfaces with extreme radii of curvature down to 6 millimeters, requiring local strain capabilities of up to 9.5 percent. These structural displays open up new avenues for seamlessly integrated wearable electronics, automotive interior curved surfaces, and highly conformed spherical VR headsets.
In this short video, you can learn:
* The performance comparison between positive Poisson's ratio PDMS and negative Poisson's ratio auxetic substrates
* Why conventional flexible displays crumble and fold on double-curved 3D surfaces
* How meta-displays conform to spherical geometries with a radius of curvature down to 6mm under 9.5% strain
š **Clip Abstract** This clip presents a side-by-side comparison of conventional PDMS-based stretchable displays and auxetic meta-displays on spherical surfaces. The presenter shows how a negative Poisson's ratio prevents buckling and crumbling, allowing perfect conformance to double-curved 3D geometries.
#AuxeticMetaDisplays, #NegativePoissonsRatio, #StretchableMicroLEDs, #IsotropicExpansion, #FlexibleElectronics, #WearableElectronics