Electrowetting Sweat Droplet Transport for Time-Resolved Sensing
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Solution Overview
Problem
Conventional sweat sensing solutions require complex microfluidics and sensors, are ineffective for small sweat volumes, and mix sweat from different times, leading to unreliable biomarker measurements, especially in sedentary individuals with low sweat rates.
Innovation Solution
An apparatus with radially grouped chambers and an electrowetting arrangement using chargeable electrodes and conductive traces to transport sweat droplets efficiently to sensors, minimizing evaporation and complexity by reducing the need for vertical interconnect access (VIA) connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional microfluidics and sensors are used for sweat monitoring, then continuous monitoring capability is achieved, but device complexity increases significantly
Solution Approach 1:
The patent extracts the complex microfluidics and sensor systems from the sweat monitoring function, replacing them with a simple electrowetting-based droplet transport mechanism. The chambers collect sweat passively and electrowetting electrodes transport the droplets directly to the sensor, eliminating the need for complex microfluidic channels and active pumping systems.
Solution Approach 2:
The patent replaces mechanical microfluidic systems with an electrowetting-based system. Instead of using mechanical pumps, valves, and complex fluidic channels to transport sweat, the invention uses electrical fields to manipulate droplet movement, significantly simplifying the mechanical complexity of the device.
2Quantity of substance
If sweat is collected over prolonged periods, then sufficient sweat volume is obtained, but sweat from different times mixes leading to unreliable biomarker measurements
Solution Approach 1:
The patent segments the sweat collection process into discrete temporal units using separate chambers for different time periods. Each chamber collects sweat during a specific time window, and electrowetting transports these segmented droplets sequentially to the sensor, preventing mixing and enabling reliable time-resolved biomarker measurements.
Solution Approach 2:
The patent performs preliminary segmentation of sweat collection into distinct temporal chambers before transport. By pre-organizing sweat samples from different time periods into separate chambers, the system ensures that biomarker measurements can be accurately correlated with specific time points without post-collection mixing.
3Speed
If electrowetting plates with hydrophobic dielectric layers are used, then sweat transport is achieved, but small sweat volumes evaporate and the process becomes time-consuming
Solution Approach 1:
The patent uses a hydrophilic coating on the chamber surfaces and outlets, creating a flexible interface that prevents evaporation while allowing controlled sweat release. This thin film approach maintains sweat volume integrity during the electrowetting transport process, especially for small droplet volumes.
Solution Approach 2:
The patent changes the surface properties of the chamber outlets from hydrophobic to hydrophilic, fundamentally altering the interaction between sweat and the surface. This parameter change prevents evaporation and ensures complete droplet formation and release, enabling rapid transport of even small sweat volumes without loss.
4Ease of manufacture
If radial grouping of chambers is implemented, then manufacturing complexity is reduced, but electrode connection complexity increases
Solution Approach 1:
The patent merges multiple electrode connections by implementing a shared reference electrode and using a common ground connection for all electrowetting electrodes. This merging approach maintains the radial chamber grouping for manufacturing simplicity while reducing the overall connection complexity through shared electrical pathways.
Solution Approach 2:
The patent implements a universal reference electrode that serves all electrowetting operations across the radially grouped chambers. This multi-functional electrode design eliminates the need for separate reference connections for each chamber, reducing overall connection complexity while maintaining the manufacturing advantages of radial grouping.
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 rapid and reliable biomarker detection by transporting discrete sweat droplets to sensors, reducing detection time from hours to minutes, suitable for sedentary individuals, and simplifying manufacturing and reducing costs.
Implementation Method 1
an electrowetting arrangement comprising: a plurality of electrodes, each electrode being electrically chargeable and dischargeable
Data Source
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AI summary
Provided is an apparatus (100) for transporting sweat droplets. The apparatus comprises a plurality of chambers for filling with sweat. Each chamber is defined in a substrate, and has an inlet lying adjacent the surface of the skin. The inlet permits sweat to enter and fill the chamber. Each chamber also has an outlet, delimited by a surface of the substrate, from which a sweat droplet protrudes once the chamber has been filled. The outlets are radially grouped around a central portion (135) of the surface of the substrate to define at least first, second and third groups of chambers. The apparatus further comprises an electrowetting arrangement comprising a plurality of electrodes. Each of the electrodes is electrically chargeable and dischargeable. The electrowetting arrangement comprises at least first, second, and third limbs of electrodes (134, 136, 138) configured to permit transport of the sweat droplets centrally from the first group in the case of the first limb, centrally from the second group in the case of the second limb, and centrally from the third group in the case of the third radial portion by charging and discharging of the electrodes. The electrowetting arrangement also includes a conductive trace arrangement (140A-O; 142A- O) arranged to electrically connect electrodes of the first, second, and third limbs to each other.