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ABSTRACT: We present a versatile and flexible method to sequentially self-assemble micron-scale components at specific locations onto unconventional substrates, such as glass and plastic. In this method, components are independently batch fabricated and assembled onto a series of receptor sites incorporated onto a substrate in a fluid medium. Initially, all self-assembly sites are blocked with a photoresist polymer. Controlled light exposure can be used to remove the polymer and make a site available for receiving a microcomponent. By repeating this procedure, various microcomponents may be integrated onto specific locations on the substrate. To demonstrate the process, we prepared four types of 20 μm thick, 320 μm diameter circular silicon components and showed their optically controllable self-assembly in arrays of 640 receptor sites on glass and plastic with yields reaching 85%. The integration and operation of two types of functional components, red light-emitting diodes and silicon resistors, on plastic substrates was also demonstrated.
Journal of Materials Research. 01/2011; 26(02):268 - 276.
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ABSTRACT: We present a simple and versatile method for integrating submicron objects onto pre-determined locations on a substrate. The method relies on augmenting inertial forces using centrifugal motion and geometric constraints to guide the placement of submicron objects on a substrate with minimal requirements for surface engineering and binding chemistries. Here, we demonstrate the utility of the method for placing gold particles, metal nanorods and inorganic nanocrystals. The method has demonstrated high yield of self-assembly for submicron particles with a variety of shapes and sizes. We have been able to get a near-perfect yield for filling hundreds of traps with nanoparticles in only 20 min. Two hundred nanometer diameter nanorods were self-assembled into an array of 256 traps on the template with 92% yield. 1.4 microm and 300 nm sodium chloride crystals were self-assembled in arrays of 7000 and 576 traps, respectively, with near-perfect yield in filling each site. Due to its convenient set-up and high performance, inertially assisted self-assembly can be easily adopted and used for a variety of integration needs on the submicron scale.
Nanotechnology 09/2010; 21(37):375604. · 3.98 Impact Factor
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ABSTRACT: Self-assembly is a promising technique for fast and cost-effective integration of microcomponents especially at smaller scales. Methods are needed to program the self-assembly process so that we can assemble heterogeneous components necessary to build a complex system. Here we present a new method of programming the self-assembly process which is based on optically removing blocking polymer from designated receptor sites. In order to perform the self-assembly process we need to fabricate free-standing microcomponents and templates. Templates were fabricated on both plastic and glass. We have shown successful assembly of four types of silicon microcomponents on plastic. The blocking AZ4620 resist was removed from the designated receptor sites immediately prior to the assembly of the desired microcomponents by using optical masks, UV exposure, and resist developer. 98% yield of proper positioning of microcomponents on a plastic template was achieved within ~10min of pipetting the components onto a template in a fluidic medium.
Micro Electro Mechanical Systems, 2009. MEMS 2009. IEEE 22nd International Conference on; 03/2009
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ABSTRACT: We present high-yield self-assembly results of silicon microcomponents assembled onto plastic substrates. The self-assembly is achieved by engineering the fluid flow over the substrate containing an array of microfluidic traps. This simple self-assembly method has demonstrated physical yields exceeding 90% as well as electrical connections between the microcomponents and the substrate. Using templates with 1250 binding sites, we were able to study the statistical nature of the self-assembly process experimentally and determine two exponential spatial and temporal trends affecting the overall yield.
Automation Science and Engineering, 2008. CASE 2008. IEEE International Conference on; 09/2008
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ABSTRACT: In this paper, we demonstrate the integration of high-performance single crystalline inorganic μ-light emitting diodes (LEDs) onto unconventional substrates such as plastic and glass via self-assembly. AlGaAs-based free-standing red μ-LEDs were batch fabricated and released from their substrates for use in self-assembly. The templates for assembly were fabricated on substrates such as flexible plastics and glass. The self-assembly method is capable of positioning the micro-components onto the template in proper receptor sites with a high yield, and forming electrical connections between components and the template with 62% yield. The μ-LEDs remain functional even after significant bending and deformation of the plastic substrates. The self-assembly method offers a way to incorporate optoelectronics onto objects that are incompatible with conventional semiconductor manufacturing processes.
Journal of Micromechanics and Microengineering 06/2008; 18(7):075019. · 2.11 Impact Factor
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ABSTRACT: Conventional contact lenses are simple polymer structures primarily used for the correction of vision. In this paper, we present a set of microfabrication techniques that allow for integration of various micro-devices onto a contact lens. The integration of function into the structure of a contact lens opens a number of intriguing venues such as incorporation of a semi-transparent display directly on the structure of a contact lens or the inclusion of a bio-sensor directly on the surface of the cornea. We also discuss methods used to render the lens biocompatible for use in a rabbit eye.
Micro Electro Mechanical Systems, 2008. MEMS 2008. IEEE 21st International Conference on; 02/2008
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ABSTRACT: We present the use of self-assembly to integrate a large number of free-standing microcomponents onto unconventional substrates. The microcomponents are batch fabricated separately from different semiconductor materials in potentially incompatible microfabrication processes and integrated onto unconventional substrates such as glass and plastic. These substrates offer a number of unique attributes as compared with silicon such as transparency, flexibility, and lower cost. Here, we provide an overview of the self-assembly process, describe how microcomponents that can participate in the self-assembly process can be mass-produced, and discuss initial self-assembly experimental results. Our results indicate that even with a very simple set-up, self-assembly yields as high as 97% for components as small as 100 mum are achievable, making the self-assembly technique immediately comparable with (or better than) the state-of-the-art robotic pick-and-place systems. We discuss various parameters that affect the yield of the self-assembly process and a possible automation scheme.
Automation Science and Engineering, 2007. CASE 2007. IEEE International Conference on; 10/2007
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ABSTRACT: We present the design and a method of construction for micro-displays via integrating free-standing micro light emitting diodes (LED) onto unconventional substrates using fluidic self-assembly. The micro LEDs are fabricated on AlGaAs substrates and released into a powder-like collection of microcomponents. The display substrate is a plastic template patterned with metal interconnects and a photopatternable polymer (SU8) to have a 4times4 array of binding sites each containing areas covered by a low melting point alloy. To assemble the display, the plastic substrate is inserted in a heated acidic ethylene glycol solution and the micro LEDs are released on the surface. Self-assembly of LEDs onto the binding sites aided by shape recognition, capillary forces resultant from the molten alloy, gravity, and fluidic forces completes the display. The self-assembly method allows for integration of crystalline semiconductor devices on plastics and other substrates that are incompatible with conventional microfabrication processes.
Micro Electro Mechanical Systems, 2007. MEMS. IEEE 20th International Conference on; 02/2007
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ABSTRACT: We present the current progress towards a fully integrated fluorescence detection system constructed via self-assembly of independently microfabricated excitation sources and photosensors onto a common template. The system template contains specifically shaped binding sites for micron-scale components and electrical interconnects. The self-assembly process allows for using materials such as plastic or glass for constructing the template that are incompatible with conventional microfabrication processes. The excitation sources are AlGaAs light emitting diodes and the photosensors are silicon pn junctions. These microcomponents are independently microfabricated and released from their respective substrates to yield a powder-like collection. The microcomponents are introduced over the template in a heated fluidic slurry and allowed to self-assemble onto the complementary-shaped binding sites. The self-assembly process is driven by capillary forces resultant from low melting point alloy coated on the electrical contact pads, fluidic forces, shape matching, and gravity. The final system offers a 3 times 3 array of individually addressable complete fluorescence detection units.
Nano/Micro Engineered and Molecular Systems, 2007. NEMS '07. 2nd IEEE International Conference on; 02/2007
