Flexible IC Microfluidic Integration via Liquid Metal Interconnects
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Solution Overview
Problem
Current flexible electronic systems lack high performance, low power consumption, scalability, and integration of fluidic functions, limiting their ability to measure biomolecular markers in bodily fluids for disease diagnosis and treatment monitoring, and face challenges in integrating solid-state ICs with microfluidics due to complex packaging and incompatibility with flexible substrates.
Innovation Solution
A novel flexible IC/microfluidic hybrid integration method using a single elastomer substrate with liquid metal interconnects and microfluidic channels, allowing seamless integration and packaging without post-processing, utilizing polydimethylsiloxane (PDMS) and gallium-indium-tin eutectic alloy (Galinstan) for electrical and fluidic connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wire bonding structure is used for IC packaging, then electrical interconnects are established, but integration with microfluidic devices becomes extremely difficult due to three dimensional structure
Solution Approach 1:
The invention extracts the electrical interconnect function from the traditional wire bonding structure and relocates it to the flexible substrate plane. Conductive traces are printed directly on the flexible substrate to establish electrical connections, eliminating the need for three-dimensional wire bonding structures and enabling straightforward microfluidic device integration on the same substrate plane.
Solution Approach 2:
The invention transitions from three-dimensional wire bonding to two-dimensional planar conductive traces on the flexible substrate. This dimensional change simplifies the overall structure and enables co-planar integration of microfluidic devices with the IC package, as both components now exist on the same two-dimensional flexible substrate plane.
2Shape
If flip-chip bonding is used for packaging, then flat device surfaces are achieved, but active surface becomes buried within the package and inaccessible for microfluidic integration
Solution Approach 1:
Instead of inverting the IC chip as in flip-chip bonding, the invention inverts the approach by keeping the IC chip in its standard orientation and achieving flatness through the flexible substrate conformal mounting. The IC chip is mounted on the flexible substrate which conforms to the chip surface, providing flatness without burying the active surface, thus enabling microfluidic integration.
Solution Approach 2:
The invention uses a flexible substrate as a conformal mounting medium between the IC chip and the package. This flexible substrate provides the necessary flatness for packaging while maintaining accessibility of the IC active surface, as it conforms to the chip surface rather than covering it completely. The flexible substrate acts as a thin film that enables both flatness and accessibility simultaneously.
3Reliability
If complex post-processing and packaging steps are used for IC/microfluidic integration, then integration is achieved, but fabrication techniques become incompatible with flexible substrates
Solution Approach 1:
The invention performs preliminary actions during the substrate fabrication process itself. Microfluidic channels are molded into the flexible substrate during its manufacturing, and conductive traces are printed on the substrate before final assembly. This preliminary integration of electrical and fluidic pathways eliminates the need for complex post-processing steps and ensures compatibility with flexible substrate fabrication techniques.
Solution Approach 2:
The invention merges the fabrication of electrical interconnects and microfluidic channels into a single substrate manufacturing process. Both the conductive traces and microfluidic pathways are created during the flexible substrate fabrication, combining what would traditionally require separate packaging steps into one integrated manufacturing process that is compatible with flexible substrates.
4Shape
If current flexible electronic systems use organic molecules or ultrathin inorganic semiconductor membranes, then flexibility is achieved, but charge-carrier mobilities are low or fabrication processes become delicate
Solution Approach 1:
The invention uses a flexible substrate as an intermediary platform that hosts rigid IC chips with high-performance semiconductor devices. The flexible substrate provides the necessary flexibility and conformability, while the rigid IC chips provide high charge-carrier mobility and robust fabrication. This intermediary approach allows the system to benefit from both flexibility and high-performance semiconductor characteristics without compromising either property.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables high-performance, low-cost, scalable, and flexible integration of ICs with microfluidics, providing biosensing capabilities and enabling previously impossible functions like heat management and metallic optofluidic components, with improved sensitivity and throughput for molecular monitoring.
Implementation Method 1
dedicated microchannels filled with liquid metals (or low melting point solders) to provide electrical interconnects to a CMOS IC chip
Implementation Method 2
enabling previously impossible functions like heat management
Data Source
AI summary
A flexible IC/microfluidic hybrid integration and packaging method and resulting device. A single flexible elastomer substrate, such as polydimethylsiloxane (PDMS), has dedicated microchannels filled with liquid metals (or low melting point solders) to provide electrical interconnects to a solid-state IC die, such as CMOS, and additional microchannels for hybrid integration with microfluidics without performing any post-processing on the IC die. The liquid metal used can be a gallium-indium-tin eutectic alloy (also called Galinstan).