Micro-scale thermal wire microphone for high frequency detection

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Solution Overview

Problem

Conventional 'hot-wire' microphones are limited to low frequency applications due to their large heated wires and long time constants, making them unsuitable for high frequency detection and fabrication on rigid or flexible substrates.

Innovation Solution

The development of micro-wire sensors with multiple resonance modes and low thermal mass, allowing for the formation of large arrays on flexible or rigid substrates, which utilize a conductive sensing element suspended above a substrate, heated or cooled to detect acoustic waves through changes in electrical conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional hot-wire microphones use large heated wires, then the microphone can detect low frequency sounds, but the time constant for cooling becomes long making it unsuitable for high frequency applications

Engineering Contradiction:

Improvelow frequency detection capabilityVSAvoidtime constant

Core Design Contradiction:

Measurement precisionVSDuration of action of moving object

Solution Approach 1:

The patent changes the physical parameters of the sensing element by reducing its size from conventional wire dimensions to micro-scale dimensions (thickness of 10-100 nm), which fundamentally alters the thermal mass and cooling time constant while maintaining the hot-wire detection mechanism

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The sensing element is divided into discrete micro-scale segments or structures (such as suspended bridges or cantilevers) rather than continuous wires, allowing for reduced thermal mass while maintaining structural integrity and detection functionality

Inventive Principle:

Principle #1Segmentation

2Device complexity

If conventional hot-wire microphones use large heated wires, then the microphone structure is simple, but it cannot be fabricated on rigid or flexible substrates in arrays

Engineering Contradiction:

Improvemicrophone structure simplicityVSAvoidfabrication on substrates

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The patent replaces conventional mechanical wire winding and mounting techniques with micro-fabrication processes (such as sputtering, evaporation, or lithography) that are standard in the semiconductor and flexible electronics industries, enabling array fabrication on substrates

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The sensing element design is made universal by using standard micro-fabrication compatible materials and processes that can be applied to both rigid and flexible substrates, allowing the same design to be manufactured in arrays across different substrate types

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Duration of action of moving object

If the sensing element is made smaller to reduce thermal mass, then the response time improves for high frequency detection, but the sensing element becomes more difficult to fabricate and secure to substrates

Engineering Contradiction:

Improveresponse timeVSAvoidsensing element fabrication precision

Core Design Contradiction:

Duration of action of moving objectVSManufacturing precision

Solution Approach 1:

The patent specifies optimized parameter ranges for the micro-scale sensing elements (thickness of 10-100 nm, specific length-to-width ratios, and controlled gap distances) that balance thermal response time with mechanical stability and fabrication feasibility using standard micro-fabrication techniques

Inventive Principle:

Principle #35Parameter changes

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

These sensors provide a wide band frequency response, enabling sound measurement at frequencies where conventional approaches are ineffective, with fast response times and the ability to form arrays for multiple location or large area sensing.

Implementation Method 1

The sensing element is typically heated or set to a predetermined temperature different from an ambient temperature so that vibration of the sensing element cools or heats the sensing element, changing sensor element electrical conductivity

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a sensor circuit coupled to the sensing element and operable to heat the sensing element

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 3

vibration of the sensing element cools or heats the sensing element, changing sensor element electrical conductivity

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20240223969A1Roll-to-roll micro-scale thermal wire microphone

Publication Date: 2024.07.04 NIKON CORP

AI summary

Micro-wire sensors comprise a conductive sensing element situated above a substrate. The sensing element can be fixed to the substrate at one or more ends and can be formed by patterning a conductive layer deposited on a flexible or other substrate. Conductive connecting pads and bias resistors can be formed with the sensing element in a common conductive layer.