HydrObserve - stopping dehydration deaths

An automated system that helps the elderly to stay hydrated and therefore prevents hospitalizations and deaths. Saving millions $.

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HydrObserve is a system that automates the task of liquid intake monitoring for the elderly.
A modular sensor device measures a drunk volume of liquid reliably and transfers the data automatically to a smartphone or tablet.
Here, warnings pop up (if hydration is low), the data is visualized and sent to an online database for automatic documentation.

Dehydration, the lack of water within the human body, is a serious issue for the elderly. In Germany alone, it was diagnosed 100.764 times in 2015, causing thousands of deaths and over 275 millions of healthcare spendings.

The good thing is, that dehydration is absolutely preventable. HydrObserve aims to investigate a possible solution.

The device is compact, usable, affordable, modular, robust, exact and low power!

You don’t drink? You die!

Dehydration (the lack of water within the body) is a serious threat. You may feel thirsty if your body wants to get hydrated, but your grandma probably doesn’t. As the feeling of thirst decreases with age, the need of water intake rises, due to reduced kidney functionality and more medication which needs to get washed out of the body. High demand of water with low liquid intake = problem. In in 2015, in Germany alone 100.764 people, mostly older than 70, got hospitalized with the primary diagnosis “acute dehydration”, leading to direct costs of more than 275 mio. € for the health system. Not speaking of the > 5000 deaths, and all the suffering and costs related to the possible implications of dehydration: paradox diarrhea, fall, cardiovascular diseases, kidney malfunction.

Why doesn’t anybody do something against dehydration?
Well, people do. Risk patients are monitored with a so-called hydration protocols, a table where the nurse notes down the volume of drinks given to the person of concern, a daily sum is calculated and – if too little was drunk – alarms are raised.

The problem with this approach: it takes the nurse some minutes every day. Time in nursing homes is expensive, and for that reason hydration-protocols are usually not applied in all, but only few cases of higher risk. But it is not these high-risk cases, which result in all these deaths and millions of costs. It’s the sum of those individuals, who are not monitored.
Solving the problem by automation

If in the current state of care liquid intake is not monitored because of the additional time needed for this task, then there is the need to automate fluid intake monitoring.

In other words: we want to minimize the time of human interaction needed for this task. Today, human interaction is needed in two major categories of liquid intake monitoring:

  • Measurement of volume: the caregiver estimates/measures the content of a cup and note it down on a piece of paper.
  • Evaluation and documentation: end of the day, the caregiver manually sums up all registered volumes, decides if hydration is sufficient and files the table which was used for documentation.

-> We need a sensor device, that automatically measures the drunk volume. To reduce errors (e.g. spilling), it would be best to do so as close to the process of drinking as possible.

-> The measured data should be analyzed and processed automatically. The human should only be needed to act if the hydration level is low.

With these two points and the requirements in mind, the following architecture seems legit:

Additional requirements

  • Compact: The sensor device is small enough to be added to everyday drinking equipment
  • Usable: everybody’s grandma should be able to use the device.
  • Affordable: no expensive medTech product. Affordable for everyone!
  • Modular: the device is not be limited to only one cup or bottle. It is possible to use it with the different containers we use when drinking every day.
  • Robust: the device must withstand regular conditions in a nursing home. All parts in contact to liquid can survive the dishwasher.
  • Exact: The accuracy of measurement is comparable to today’s practice
  • Low power: A small coin cell can power the device for weeks.

Note: This project is a private developement as follow-up of research which was done by J. Kreutzer, J. Deist and myself at the Institute of Micro Technology and Medical Device Technology (MIMED) at the Technical University of Munich. Results of the research were published here. HydrObserve as private project is fully permitted by Prof. T. Lüth, the chairholder.

All progress will be documented intensively in the build logs. Only major advances are added here in brief comments.


  1. Found the perfect sensor for this application: a tiny magnetic turbine + hall sensor (log 1).
  2. Used materials of Chinese sensor pass basic food safety test (log 2).
  3. The architecture of the device will be modular and with this avoid problems of available solutions...
Read more »

  • Idea of a modular architecture of the device

    jflaschberger3 days ago 0 comments

    Defining Requirements

    With the flow sensing element being defined (ferrite-flow-capsule and hall sensor), we can now think of the architecture of our sensor device. Because we use a hall sensor for detection, we gain the freedom to have some millimeters in distance between the spinning ferrite and hall sensor.

    At first, we must resist the engineer’s urge to start off designing a cool new, high tech, flow measuring, IOT drinking device (with lasers!). Something like the “Hydracoach Water Bottle”, a commercial product which comes close to what we try to develop here. It was even tested for its usability in care, and apart from many disadvantages, the test users disliked it purely for the fact that they had to drink from this massive, heavy piece of plastic. Instead, they wanted their cup back, with which they used to drink before.

    Note: the device has to be somehow small and more something you put IN BETWEEN the cup and your mouth when drinking, not a new futuristic drinking vessel (even if it has lasers).

    During my experiments with the flow sensor (see last update), I destroyed one ferrite-flow-capsule by drinking orange juice with tiny pieces of fruit pulp in it (the ferrite got stuck). It might be a good idea to build the device in such a way that the capsule could be replaced.

    Oh, and everything in contact with liquid should survive the dishwasher. Either the electronics need to be capsuled (-> wireless charging neccessary) or the electronics must be detachable.

    Solution for architecture

    The device consists of two major units: the mouthpiece (3) and the sensor unit (2).

    The mouthpiece is the part the liquid passes through when drinking. In the hollow center, the ferrite capsule (4) is fixed. Oh, yes and the mouthpiece is put to the mouth when drinking.

    The sensor unit contains all the electronics, battery and the hall sensor. It is attached to the mouthpiece by a detachable connection, in a piggyback-way.

    Here are the benefits of this approach:

    • The mouthpiece is the unit most likely to fail during use (it contains a moving part). It is a simple piece of cheap plastic and can be easily cleaned or replaced. No electronics get wasted.
    • The “personalization” of the device happens, when the sensor unit (registered to one user) is attached to a mouthpiece. With this, drinks for a whole floor of a nursing home can be prepared including the mouthpiece, not having to think of which coffee is for whom. The user makes the cup his/hers by attaching his/her sensor unit. Mouthpieces are interchangeable, sensor units are personal.
    • The mouthpiece can have any desired shape, as long as the ferrite-capsule fits inside and the mechanical interface to the sensor unit is maintained. With the same electronics, various variants of the mouthpiece can be developed: it could be used with a straw (A), screwed onto a bottle (B) or as the lid of a feeding cup (C).

  • Food safety check for chinese ferrite sensor part

    jflaschberger06/15/2017 at 08:19 0 comments

    Before we continue building HyrOserve, we should check if the device may kill ourselves. Ordering components from China to mix them with food/drinks may end up with a lead poisoning!

    The Chinese manufacturer of the small ferrite-turbine-capsule that we use for this project is quite responsive to emails and provided me with a “food grade safety” certificate of the device (see project files), which unfortunately only contained information and tests for the plastic used for the housing(POM), not for the ferrite capsule. I asked the manufacturer for more information and got the response:

    • shell : POM food grade material
    • impeller : plastic + magnetic
    • rotation shaft : SUS304

    Alright. That the shell should be fine, they seem to get their plastic tested. The rotation shaft is made from a SUS304, a high grade stainless steel, and I tend to trust people who know the type code of the steel they use. What makes me suspicious is the “plastic + magnetic” of the impeller.

    I don’t have the money to pay for a food grade testing, so we may stick to a more basic approach for now. Take the ferrite impeller, cut some piece and observe the fresh cutting edge. If it doesn’t look oxidized after some days in different chemical baths, no toxic particles should dissolve in a liquid while drinking.

    For the test, I did the following:

    1. I scratched and crushed the ferrite material, observed it under a microscope.
    2. These pieces were put in two different chemical baths for 36 hours. Bath one: water with 20% table salt. Bath two: water + 30% industrial detergent + 5% phosphoric acid.
    3. Observe the chemical baths. Any changes in color?
    4. Clean and dry the pieces, observe it under a microscope.

    Here are some pictures before the bath:

    ...and here under the microscope (300x)

    ...the bathes with saltwater and acid enriched detergent

    Results: The ferrite material didn't change at all. The baths stayed cristal clear (after the foam on the right jar settled). Under the microscope, the fracture planes looked identical to the state before the treatment, and sharp edges stayed sharp. Visually, no differences between both chemicals could be detected.
    --> orange juice and the dishwasher are not likely to dissolve the ferrite and with it toxic elements. This is not a real food grade test, but I feel safe now when drinking through the HydrObserve sensor that I'm going to build. So, let's get startet!

    Here now similar pictures after the bath:

  • Finding the right sensor for the application

    jflaschberger06/11/2017 at 14:23 0 comments

    Ok, this now is one of the most fun tasks in development: finding the adequate sensor for our application. Wait: what was our application? Ah, yes: Fluid volume measurement in the process of drinking.

    If you ask your favorite web search for “flow sensor” you will be overwhelmed by the range of possible devices and sensing principles, which I don’t want to discuss here is detail. Let’s narrow it down to what we need:

    • size: small sensor, which we can fix to a cup
    • price: it should only cost a few bucks
    • detactable flow speed should cover the range of slow drinking (no liters/second)
    • food safety of the used materials

    With these requirements, we end up with a way smaller range, and all possible sensors there work with the same principle: the moving fluid forces the rotation of a small magnet. The magnet’s alternating field is detected by a hall sensor. As hall sensors come as tiny, simple and cheap components, we can even ignore the sensor’s electronics and build our own. Perfect for hacking! And – probably even more important – a we do not need a direct contact between the hall sensor and the fluid. The magnetic field easily penetrates through some mm of plastic.

    I ordered a few samples of the device type “MJ-HZ41WB” from a Chinese manufacturer, selling for 5$

    Tests with this sensor were quite successful. Using an Arduino to count the pulses of the hall sensor while drinking through it, I got reproducible results. The values were quite close to the linear graph provided with the datasheet:

    Playing with the device, I discovered that the sensor contained a tiny capsule with the moving magnet, secured by a small metal retainer ring. One sensor got sacrificed to get this capsule out, and [wow!], what an example of clever engineering! The plastic capsule itself serves as the bearing and the flow manipulation mechanism. As you can see in the pics, one side has turbine-line shovels in the fluid’s path, which make the fluid spin. The spinning fluid in return applies a force on the cross-shaped magnet and makes it turn. The rotation speed correlates with the speed of the fluid passing through.

    I have seen different, expensive sensors with a complex, magnetic micro-turbine inside. Here, the magnetized ferrite can be a simple cross, the PTFE housing serves as excellent bearing. Simple and cheap.

    So: the whole functionality of the flow sensor is more or less contained within this tiny capsule, which could be easily integrated in any other structure. I contacted the manufacturer and asked if I could get the capsules only, and I did. They cost only incredible 1$ if ordered in larger quantities. What a perfect start for a promising project!

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