MEMS Ultrasonic Transducer Fluidic Damping for Blind Zone Reduction
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Solution Overview
Problem
Existing MEMS ultrasonic transducers face challenges in detecting close objects due to the superposition of emitted and reflected waves, resulting from insufficient damping of membrane oscillations, especially in low-density propagation media like air, which increases the minimum detectable distance and complicates distance measurement.
Innovation Solution
The MEMS ultrasonic transducer device incorporates a semiconductor body with a fluidic recirculation path and a piezoelectric element, where the membrane oscillations are enhanced by a central and lateral fluidic passages and trenches, allowing air recirculation that increases damping and reduces the ring-down interval, thereby preventing wave superposition and improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the membrane oscillation damping is reduced to improve detection sensitivity, then the ring-down interval increases, but the emitted and reflected waves superimpose causing blind zone
Solution Approach 1:
A fluid medium (gas or liquid) is introduced as an intermediary between the membrane and the external environment. This fluid circulates through channels in the substrate and provides acoustic loading that dampens membrane oscillations during the ring-down phase, preventing wave superposition while maintaining detection capability.
Solution Approach 2:
The patent employs a fluidic system where gas or liquid circulates through channels formed in the substrate. The fluid provides pneumatic/hydraulic loading on the membrane背面, creating acoustic damping that reduces the ring-down interval and prevents superposition of emitted and reflected waves, thereby eliminating the blind zone.
2Loss of time
If the ring-down interval is shortened to reduce blind zone, then damping is increased, but detection accuracy may be compromised
Solution Approach 1:
The circulating fluid acts as an intermediary that provides controlled acoustic loading. The fluid's density and viscosity can be selected to achieve optimal damping that shortens the ring-down interval while preserving sufficient oscillation amplitude for accurate echo detection.
Solution Approach 2:
The patent allows changing physical parameters of the fluid medium (such as gas type, pressure, or liquid viscosity) to optimize the damping characteristics. By adjusting these parameters, the system achieves the desired balance between reducing blind zone and maintaining detection accuracy.
3Loss of energy
If passive or active dampers are added to increase damping, then device complexity increases, but manufacturing integration becomes difficult
Solution Approach 1:
The damping function is merged with the substrate structure itself. Channels are formed directly in the substrate during manufacturing, and the fluidic damping system is integrated into the transducer's existing architecture, eliminating the need for separate passive or active damper components.
Solution Approach 2:
The circulating fluid provides self-regulating damping through its natural acoustic properties. The system uses the fluid's inherent resistance to membrane motion to provide damping without requiring external control mechanisms or additional components, achieving energy dissipation through the fluid's natural behavior.
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
The enhanced damping of membrane oscillations increases the minimum detectable distance and improves measurement accuracy by reducing the risk of wave superposition, allowing for more precise object detection without requiring additional signal processing algorithms, and minimizing dependence on external factors.
Implementation Method 1
the ultrasonic transducer T comprises a membrane which, for example piezoelectrically or capacitively, is controllable to oscillate in order to generate the emitted wave W e
Implementation Method 2
allowing air recirculation that increases damping and reduces the ring-down interval
Data Source
Figure 1~2
Figure 3~5
Figure 6A~6B
AI summary
MEMS ultrasonic transducer, MUT, device (1), comprising a semiconductor body (3) with a first (3A) and a second (3B) main surface and including: a first chamber (15) extending into the semiconductor body (3) at a distance from the first main surface (3A); a membrane (18) formed by the semiconductor body (3) between the first main surface (3A) and the first chamber (15); a piezoelectric element (19) on the membrane (18); a second chamber (20) extending into the semiconductor body (3) between the first chamber (15) and the second main surface (3B); a central fluidic passage (22) extending into the semiconductor body (3) from the second main surface (3B) to the first chamber (15) and traversing the second chamber (20); and one or more lateral fluidic passages (21) extending into the semiconductor body (3) from the second main surface (3B) to the second chamber (20). The one or more lateral fluidic passages (21), the central fluidic passage (22) and the second chamber (20) define a fluidic recirculation path that fluidically connects the first chamber (15) with the outside of the semiconductor body (3).