Porous Silicon MEM Pump for Gas Flow and IC Cooling
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Solution Overview
Problem
Existing microelectromechanical (MEM) devices lack efficient gas pumping solutions with moving parts and require external power for cooling, limiting their miniaturization and integration with other gas-phase MEM devices.
Innovation Solution
A MEM pump utilizing a porous silicon region with predetermined pore sizes between 10 nanometers to 10 microns, driven by a thermal gradient, which allows for the integration with other MEM devices and passive cooling of integrated circuits without external power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional MEM devices use moving parts for gas pumping, then pumping function is achieved, but device complexity and reliability are worsened due to mechanical components
Solution Approach 1:
The patent replaces mechanical pumping components with a thermal transpiration pump that uses thermal gradients to drive gas flow through porous silicon structures. This eliminates moving parts, seals, and mechanical actuators, substituting them with a passive thermal field-based mechanism that achieves pumping through temperature differential across the porous medium.
Solution Approach 2:
The invention utilizes porous silicon as the pumping medium, where gas flow is controlled through the porous structure's pore network. The porous material enables thermal transpiration effects to generate directional gas flow without mechanical components, leveraging the material's intrinsic pore architecture to achieve pumping functionality.
2Temperature
If external power is used for cooling integrated circuits, then cooling function is achieved, but energy consumption and device complexity increase
Solution Approach 1:
The patent enables the integrated circuit to cool itself by utilizing its own waste heat to drive the thermal transpiration pump. The IC's operational heat creates the thermal gradient necessary for gas flow through the porous silicon, which then facilitates passive cooling of the IC without requiring external power sources or active cooling systems.
Solution Approach 2:
The invention converts the harmful waste heat generated by the integrated circuit into a beneficial resource that drives the cooling process. The thermal energy that would normally be discarded is instead harnessed to power the thermal transpiration pump, creating a self-sustaining cooling mechanism that eliminates the need for external cooling power.
3Manufacturing precision
If porous silicon pore size is not predetermined, then manufacturing flexibility is maintained, but manufacturing precision deteriorates
Solution Approach 1:
The patent employs electrochemical etching parameters such as current density, etching time, and electrolyte composition to precisely control the pore size of the porous silicon structure. By adjusting these process parameters, the invention achieves predetermined pore sizes within specific ranges (e.g., 10-100 nm) while maintaining compatibility with standard semiconductor manufacturing processes.
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 efficient gas pumping and passive cooling of integrated circuits, facilitating miniaturization and integration with other MEM devices, such as chemical preconcentrators and gas chromatographs, while eliminating the need for moving parts and external power.
Implementation Method 1
thermal transpiration pumps have no moving parts, do not require oil, and can operate in any orientation. Additionally, thermal transpiration pumps are amenable to miniaturization for use with microelectromechanical (MEM) devices.
Implementation Method 2
a microelectromechanical (MEM) Knudsen pump (hereafter referred to as a MEM pump) using a porous silicon region formed in a silicon substrate
Implementation Method 3
with a cross-section dimension of each pore being substantially equal to or smaller than a mean free path length of the gas to pump the gas from the inlet chamber to the outlet chamber in response to a thermal gradient provided along a length of each pore by the heat source
Implementation Method 4
The heat source can comprise an electrical resistance heater
Implementation Method 5
the heat generated by the IC can act to pump a gas (e.g. air) through the MEM pump, with the gas being heated and thereby removing heat from the IC
Data Source
AI summary
A microelectromechanical (MEM) pump is disclosed which includes a porous silicon region sandwiched between an inlet chamber and an outlet chamber. The porous silicon region is formed in a silicon substrate and contains a number of pores extending between the inlet and outlet chambers, with each pore having a cross-section dimension about equal to or smaller than a mean free path of a gas being pumped. A thermal gradient is provided along the length of each pore by a heat source which can be an electrical resistance heater or an integrated circuit (IC). A channel can be formed through the silicon substrate so that inlet and outlet ports can be formed on the same side of the substrate, or so that multiple MEM pumps can be connected in series to form a multi-stage MEM pump. The MEM pump has applications for use in gas-phase MEM chemical analysis systems, and can also be used for passive cooling of ICs.