James R. Etzkorn

Optically Programmable Self-Assembly of Heterogeneous Micro-Components on Unconventional Substrates

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.

Forming self-assembled cell arrays and measuring the oxygen consumption rate of a single live cell

We report a method for forming arrays of live single cells on a chip using polymer micro-traps made of SU8. We have studied the toxicity of the microfabricated structures and the associated environment for two cell lines. We also report a method for measuring the oxygen consumption rate of a single cell using optical interrogation of molecular oxygen sensors placed in micromachined micro-wells by temporarily sealing the cells in the micro-traps. The new techniques presented here add to the collection of tools available for performing “single-cell” biology. A single-cell self-assembly yield of 61% was achieved with oxygen draw down rates of 0.83, 0.82, and 0.71 fmol/minute on three isolated live A549 cells.

Large scale self-assembly of crystalline semiconductor microcomponents onto plastic substrates via microfluidic traps

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 and yield of micron-scale self-assembly processes

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.

Integration of user interface, device control, data acquisition and analysis for automated multi-spectral imaging of single biological cells

Major advances in the understanding in the biological sciences have been achieved by the precision automation of repetitive analytical procedures. The requirements for precision are pushed to the extreme when considering the analysis of cell function at the single cell level. Such analyses may include examination of gene expression, protein synthesis, and metabolic activity. The repetitive nature of performing measurement of these parameters requires not only effective signal transduction and amplification, significant attention to system integration and automation is paramount to instrument development objectives. Here we present the systems integration and software development for a multi-spectral imaging and phosphorescence lifetime measurement tool. This tool represents and early engineering prototype of one subsystem of an integrated automation pipeline comprising robotics for microwell-array movement, microwell-array sealing for metabolic rate measurements, control of experimental protocol sequencing and real-time imaging of dynamic experiments. A graphical user interface and underlying control software allows for flexible construction of experimental procedures. The engineering prototype has demonstrated experimental operation times up to 10 times faster than previous manual methods.

Self-assembly of Micro-devices unto Unconventional Substrates

Active aircraft body surfaces require integration of various micro-devices and sensors over large areas. We have demonstrated a self-assembly method that is capable of integrating functional heterogeneous micro-components on unconventional substrates such as plastic and glass. This method could be applied to a very large area to functionalize the surface of an aircraft. In order to demonstrate the method, micro-components were fabricated on a carrier wafer, and released to form a powder like collection. The template was fabricated separately and was submerged inside a fluid medium during the selfassembly process. Components were introduced over the template and were self-assembled to build a functional system. In addition, we have shown two methods for programming the self-assembly process by using optical and geometrical methods to allow for an accurate placement of heterogeneous components.