A node - in the shape of a ring on an index finger - that enables data accumulation and distribution.

What is it?

Our product is called LifeRing. Initially, it started 12 months ago as an evening hobby for 4 technology engineers, who had grown frustrated with the current wearable tech market. We set out to design a wearable node that was sufficiently low powered to be wireless and effectively “chargeless” to the user, and which was sufficiently small and low profile, so as not to impinge on a user’s day-to-day life. Our ambition was to produce a reliable piece of hardware which users would need never take off – an ideal functional aspiration of the wearables industry which has yet to be fulfilled.

The node – in the shape of a ring on an index finger – uses a combination of low-power solid-state sensing peripherals, alongside a sub-threshold controller (ideally AmbiqMicro’s Cortex M4-based MCU, due to greater familiarity with ARM’s architecture), to enable data accumulation and distribution via a sufficiently low power (~0.001-0.1mW) system. It also utilises novel material selection and processing to enable sufficient thermal wicking, mechanical damping and RF shielding to the electronics system, in a low profile package, to enable a far more robust offering than current competitor offerings. Our initial design intent was to pair our node with RF-harvesting smartphone cases – such as that offered by Nikola Labs – to enable 900Mhz modulated backscatter coupling. From our 1D energy calculations, we could meet our energy budget for continuous full-functionality capability within 10m of an enabled phone casing, with sufficient back-up storage for 2 hours of reduced-functionality at distances up to 50m.

Though our design has – thankfully, and very kindly – been commended, most notably by IUK, our main weakness as a team is in business planning and strategy. We could not find a unique feature or selling point for our design over the archetypal fitness and health trackers, to encourage the level of investment required to compete in a developed nation market. We anticipated being able to focus on gesture authentication/control and medical alert features via smartphone/tablet pairing. Examples of features would include gesture control of consumer electrical goods (the ability to control lighting, TV volume, in-car controls, door locks etc through custom gestures) through smartphone pairing, and seizure/embolism alerts via monitoring of flow variation in the index digital artery, palmar skin conductance and low amplitude vibrations to derive BCG and respiratory motion. These feature sets use two novel low power sensing solutions – MCube’s IGyro (orientation and dynamics) , and EMFIT ferroelectret film (skin conductance and micro-oscillatory motions).

Our sub-threshold architecture proposal meets a strict packaging criteria, based on the dimensions of a wedding band. However, to ensure a reliable and robust product, environmental considerations must also be incorporated within this package envelope – thermal stability, impact resistance and shielding from RF interference. We chose two novel solutions in order to meet our package criteria. A thin metallic foam (0.5mm) is overlaid upon the base electronics, from Versarien, embedded in a phase-change wax. This is then consequently layered with a zinc polymer cell from Imprint, and finally, a filar-wound RF antenna. The entire assembly is over-moulded in polyurethane to seal the electronics, leaving only the EMFIT film, on the interior, exposed to the skin.

The metallic foam provides RF shielding and an incredibly dense thermal inertia, whilst the zinc polymer cell provides mechanical damping for impact resistance, in addition to it’s primary function, which is to provide ~200mWh storage, sufficient for 2-5 hours remote operation, at a distance >10m from a modulated backscatter transmitter.

When we heard of the UNICEF Wearablesforgood competition, we recognised that this could give our concept a true relevance – wireless and chargeless capabilities in the developed world are a convenience. In a developing world application, they could be considered a necessity, due to lack of charge point availability and perhaps understanding of consumer electronics operation. Rather than using coupled smartphone casings for transmission and powering, we assessed other options for off-body far-field coupling hardware, with the additional functional requirement of providing a data transmission path to the end user (a redundant requirement when in close proximity to a smartphone).

We assessed a number of potential designs for transmission bases, in lieu of the smartphone connection our previous iteration could rely upon. We were conscious that any solution must be low cost, since the transmission hardware itself is relatively generic. From our energy calculations, a transmission base with 50W supplied electrical energy could support a 300sqm transmission field (radial) with an average density of 5 nodes.

We have arrived at two potential solutions.

The first is to use recycled cell phones with dual-band edge (900Mhz) and wi-fi (2.4Ghz), with one band servicing the modulated backscatter node-to-base, and the other providing a transmission path through a network of bases, to distribute accumulated data to an end user.

The second is to use recycled dual band wi-fi routers with 2.4Ghz and 5Ghz bands. In this instance, the receiving node antenna would be redesigned for 2.4Ghz wavelengths, and the 5Ghz band would support the data transmission network.

Each solution has inherent benefits and drawbacks. Availability of discarded cell phone hardware is greater, and the hardware can provide secondary benefits such as transient energy storage in the battery, transient data storage in SRAM, and the use of the speaker for sounding audible alarms or messages. However, the ability to flash new firmware for repurposing of cell phone hardware is unknown to us, and varies from manufacturer to manufacturer. Wi-fi routers – particularly dual-band – are perceived to be less available and more expensive as an upcycling resource, but would be easier to repurpose for our application.

The most robust solution could use a combination of both ideas, but this is dependent on availability of upcycled hardware.

In remote applications, we propose using PV cells to provide power. Assuming an average 1kW incident irradiance, and a conversion efficiency of ~20%, this estimates a 0.25sqm cell per base would be sufficient. For a 300sqm service coverage, this equates to a PV density of 0.08% per unit area coverage. By way of a scaled example, half a football pitch (soccer) could service one square mile.

How is it used?

The LifeRing is worn on the index finger or thumb of the user. It is intended that each user requires only one ring, and need never return it for charging or service of any kind. We chose a ring due to its proximity to both palmar and non-palmar skin regions, it’s inherent retention close to the skin surface (avoiding failure modes of wristband wearables) and due to the fact that rings are generally regarded as nondescript from a religious or cultural perspective – from our research, we can only find evidence stating that the material of the ring could be a consideration, and that it must not be a precious decorative metal.

A ring is also a lightweight and low profile, non-intrusive wearable. We have previously stated our affinity to a “wedding band” package criteria, and this is due to the fact that we perceive the wedding band to be the only validated wearable item that “users” do not take off, regardless of activity. For instance, many would chose to remove a heavy wristwatch or fitness tracker when sleeping, washing, doing manual labour etc – some even find that they are prevented from typing or writing effectively with wrist-based items – but few remove their wedding bands. If we can replicate this attachment and experience for our wearable node, then we anticipate being able to provide a service that does not inhibit the users day-to-day livelihoods, and delivers only benefits to them and their community,

We acknowledge that the functional ideal solution is an embedded node – it is very difficult to lose a node within your body, and the user will not be able to remove it, even at their will. However, embedded nodes have obvious critical failure modes associated with their implementation, such as refusal to participate on religious or cultural grounds, the requirement for medically-trained installation and the lack of acceptability of such techniques. We want users to be enthusiastic about the benefits of wearable technologies, to encourage them to participate, and have them enjoy the features that are enabled by wearing such devices.

The rings do not communicate directly with one another; rather, their outputs are collated to a hub through the transmission network, for a variety of end users and purposes. To meet the ultra-low power requirements stipulated for this application, there is no user interface on the ring – I.e. no method of directly informing the user of outputs, such as a screen or audible alarm. There is potential however, when using recycled cell phone hardware, to repurpose the speaker functions to create audible alerts at transmission bases.

What technologies does it incorporate?

There are 3 key technology elements in our system: sensing and measurement, processing, and distribution.

The two proposed sensing technologies are EMFIT ferroelectret film and MCube IGYRO – a 9DOF instrument which uses derives rotational motion without using a power-intensive MEMS mechanical gyro element. Having extensively studied the low power sensing market, we have arrived at the conclusion that this pairing provides the greatest combined output for our energy budget and package envelope.

The overriding principle of our sensor architecture is to collate, model and derive mechanical, electrical and thermal signals to yield required outputs over time, rather than rely upon state-of-art – and power-intensive – direct optical or chemical measurements. By gauging the variability of various parameters, our system can identify users who are in need of further, dedicated attention, or alternatively can log key metrics regarding specific events, such as hand-washing. It is not intended as a encapsulated diagnosis device, rather an early warning and event detection system, to enable sufficient corrective action in a timely manner.

This list tabulates logged parameters we have chosen for our design, and the associated mechanism for measurement:

1) Heart Rate Variability – PQRST wave from digital radial artery (EMFIT) and BCG mechanical signals (IGYRO).

2) Respiratory Rate Variability – diaphragmatic reaction (IGYRO) and first derivative of PQRST wave (EMFIT).

3) Blood Pressure Variability – strain plethysmography at digital radial artery (EMFIT).

4) Skin Conductance and Temperature Variability on palmar and non-palmar contacts (front and back of finger) – indication of nervous system stimulus and emotive responses such as excitement, pain etc. Also provides indication of hands being immersed in liquid (EMFIT).

5) Foetal BCG and orientation – detection of secondary, lower-amplitude BCG vector (IGYRO).

6) Backscatter frequency tracking – detection of velocity vectors for users, through rate of change of geographic position (RF Antennae).

7) Hand position relative to transmitter base, and gesture recognition for interaction with environment (IGYRO).

One further parameter we could feasibly measure is the skin cholesterol content of the user. However, this requires a solvent to be applied to the skin, to measure conductance of the skin’s reaction. Since this would require supply of a dedicated solvent, it is not a continuous measurement capability, and the outputs tabulated above would give sufficient indication of a malnutrition risk over a time period, to alert a practitioner to the need for attention.

We will discuss the features enabled by these measurements in the use case section.

As mentioned before, the governing controller for the two sensing peripherals will be a a sub-threshold SoC device, such as AmbiqMicro’s Cortex M4-based MCU, or Psikick’s sensor platform, with embedded clock and SRAM. We intend to use a variable timestep power management strategy, whereby each channel is measured for a 5s pulse width at 50hz, on a maximum 60s repeat cycle. This yields low sampling rate data over a period >>60s, enabling long term modelling of health, wellbeing etc. A number of triggers can be employed to increase the sample rate – 60s may be sufficient overnight, but a 30-15s rate may be more appropriate during the day. There may also be discrete events we wish to log – such as hand washing, or an acuteness in respiratory rate – which can have discrete triggers coded accordingly. Implementation of this power strategy should yield a benefit in utilisation of PV cells, for instance, to enable a lower average power requirement at night, reducing the requirement for load-levelling.

The final technology element is data distribution and networking. We propose utilising either 2.4 or 0.9Ghz backscatter coupling to an onboard RF filar antennae. When not transmitting, a parallel capacitor is pumped up and then switched to load the onboard polymer cell. When a trigger to transmit data is called by the controller, a variable resistor modulates the back scattered signal from the nearest transmission base into a singulation code, followed by the data packet.

It may also be worth touching on the two other key enabling technologies in this design, which are PCM-embedded metallic foam and Zn polymer cell.

A key enabler for robust sub-threshold operation is thermal, mechanical and electromagnetic stability. This risk can be mitigated with sufficient shielding, damping and thermal inertia, but the penance of this design choice is the impact on package and weight requirements. VersarienCu is a cost-effective foam product, which we propose using as a scaffold for a phase change wax. This provides a very dense thermal inertia, enabling a wider linear temperature operation domain for the sub-threshold system. The foam also provides improved RF shielding, due to it’s continuously-varying microstructure, providing a wider spectrum of wave reflection. Finally, the flexible polymer cell – which we propose to source from Imprint Energy – provides a low profile energy storage solution, for when users are out of design range from a transmission base, but also provides a form of distributed mechanical damping to the electronics. This improves the thermal and mechanical durability of the product, compared to using non-flexible battery cells, and also contributes to a smaller overall package envelope.

How does it work?

Firstly, a user network is identified for the system. This could be, a population of women and children in a remote community. The environment is surveyed for power supply capability – perhaps there is a school or hospital with mains power, which could support some of the transmission network directly. In areas where mains power is unavailable, we propose PV cells are used to power transmission bases. Each base must be within ~20m of another, in order to provide a continuous coverage network (n.b mains powered bases could feasibly service a slightly wider area). A base consists of a 0.9/2.4Ghz transmitter, which continually broadcasts a frequency-matched signal to LifeRings in the vicinity. The transmitter provides a power input to the LifeRings nearby, whilst also detecting backscatter-modulated data. A singulation code identifies the LifeRing that is modulating the response. When a LifeRing leaves the detection area, the intention is that the next transmission base continues to service the device. Concurrently, a 2.4Ghz/5Ghz transmitter network cascades received data – via a microprocessor – through the network, in much the same way as a wi-fi booster would reamplify a signal. It is proposed that transmission bases be fabricated from upcycled cell phone or wifi router hardware. As mentioned previously, the choice of bandwidth for base-to-node/base-to-base could be 2.4/5Ghz, or 0.9/2.4Ghz respectively. This depends on the availability of recycled hardware. Ideally, a base would consist of the following:

Cell phone battery
Cell phone speaker
Cell phone RF receiver/transmitter module
Firmware upgrade or transplant microprocessor for base-to-node
Wi-fi RF receiver/transmitter module
Firmware upgrade or transplant microprocessor for base-to-base

There are two methods for communication with end users: distributed and direct.

Distributed end users (perhaps school teachers, medical professionals, UNICEF staff) would be able to receive the data through a USB-connected receiver to any laptop/PC. A simple MATlab GUI would illustrate the data in a format related to the interests of the end user. If an Internet connection is available at a location, data could be uploaded for analysis from global end users (though we assume this would not be an everyday occurrence in such locations – perhaps data for global distribution would be manually collected by a UNICEF representative every few months).

Direct end users are the wearers of LifeRing. They will be able to directly receive a pre-recorded audible alert from the transmission base, should a trigger event be detected by the base microprocessor. This could be alert of a nearby disaster epicentre, or non-detection of an expected event, such as hand washing.

Since the LifeRing node has onboard energy storage also, sufficient redundancy is provided for instances where transmission bases are out of range, or the nearest base has experienced power outage. It also enables a period of high sampling intensity during an event, to capture the required fidelity of information. We model that our specification could provide approximately 1 hour of remote sampling at maximum intensity, providing information of value when it is needed most.

The node itself has two sensing instruments: a segmented EMFIT ferroelectret film interior, and a MCube magnetometer/accelerometer. The segmented film provides a differential between palmar and non-palmar readings. The parameters for these instruments are listed in the “how it is used” section, and the enabled features are discussed in the “use case” section. Sampling is taken periodically, or following an event trigger.

Who uses it?

One of the unique selling points of our system is the variety of end user communication capabilities. We have identified the end user and method of communication for each feature in the “use case” section below.

The end user can be a wearer or LifeRing, a local authority representative (health worker, teacher, government worker etc), or a remote specialist or organisation, such as UNICEF.

Communication to end users is via three techniques, dependent on the infrastructure available.

1) Audible signals from transmission bases, to members of the community.
2) MATLab UI, or “app” to a RF receiver and laptop, for local authorities.
3) Internet uplink to a UNICEF server (if available), or manual distribution of data backed-up to a hard drive, for periodical data analysis and trend insight by remote organisations such as UNICEF – we propose one hard drive “handover” per quarter for instance, or per UNICEF visit.

Why does it help?

Here is how we have targeted the specific metrics of success for Wearablesforgood, as stated in the competition handbook:


We applied two fundamental principles in ensuring cost-effective solutions – reduce piece cost, or add value. By reducing piece cost, we mean reducing the monetary value of each product, whereas adding value can mean improving the scope of the product, or leveraging greater cost efficiencies through novel business practice.

We recognised early on in the submission process that the fundamental design of LifeRing can only be down-costed so far – the enabling features for a rugged, low-powered device stipulate a certain quality and quantity of material. To reduce cost further than this critical point would impact these other design considerations. We have therefore focussed more on novel methods for “adding value”, rather than “reducing cost”.

In reducing cost, we have specified a cheaper metallic foam manufacturing process, and identified new features for stock components, such as using the battery as an impact resistant layer. We have also opted for known, field-validated sensing components and electronics, based on proven generic hardware, to leverage the best cost efficiencies in design specification. Finally, in designing the base network, we have chosen easily-upcycled hardware – of which there is a plentiful waste stream available in developed countries as we upgrade our cell phone and router hardware frequently – to minimise total cost for a network installation.

In adding value, we have strategically chosen to offer a “one size fits all” design, to meet all use cases specified by UNICEF. This adds value by enabling one “tool” to do many “jobs”. As mentioned previously, we also anticipate the raw data being of value in as yet undetermined applications, given its generic and broad scope, adding potential value in the future. Having one “stock” design allows us to leverage greater productivity from our suppliers through increased volumes. From our research, we anticipate a minimum volume order for cost-effective production of 10k LifeRing units. We imagine it is unlikely that UNICEF will require 10k units immediately, and so we propose using the surplus volume from the first production run to produce a UNICEF-branded LifeRing, for retail in the UK, as an alternative to a charity wristband. Customers could buy a LifeRing with basic functionality to a paired case – say, gesture control, or basic biometric outputs. The profit from the sales in the UK would go to UNICEF, as with wristbands and other merchandise, whilst Perihelion Technology benefit by having a beta product in the UK market, with strong brand recognition. It is anticipated that this would greatly offset any disparity in piece cost for LifeRing over other proposals for Wearablesforgood.


One of the core values of Perihelion Technology is that wearable technology should need never be removed by the user, as the value of the product drops immensely when it has to be serviced or charged. Our design enables low-power operation through application of sub-threshold controller design, novel sleep modes, wireless backscatter coupling and simple sensing methods. This enables low-acreage PV cells to feasibly support a network of transmission bases in a matrix formation. From our calculations, our product can be sustainably operated within the network area continuously, with approximately one hour of operation from the auxiliary polymer cell during an “error state” condition (loss of network due to natural disaster, or a wearer leaving the community, for instance). We anticipate this being a sufficient duty requirement for the use cases depicted by UNICEF.

Rugged and durable

Again, a core value for Perihelion Technology, we learned from market research that current consumer electronic wearables are reported to have poor lifecycle endurance, and are highly-sensitive to climatic variation. Through novel thermal, electromagnetic and mechanical design features, we believe we have formed a design which is far more durable against harsh environmental requirements than current market offerings in the fitness tracker industry, which we used as an example. Our novel design has also enabled us to package our product in a much tighter envelope, making it less intrusive and more attractive to the end user as a product that will not inhibit them from going about their day-to-day activities.


As discussed previously, our design approach was to create a product which could be multi-derivative – that is, one tool, with many applications, as demonstrated in the “use case” section . By only having to design and validate one piece of hardware, we can dramatically cut down our time to implementation, and can easily repurpose and further populate a network by adding more bases and more LifeRing products. Since LifeRing and the network is self-governing, it does not need a technical support network to facilitate charging or calibration etc in the field. Our use of MATlab as a post-process tool also enables further features to be added in future, as the needs of the wearer and UNICEF develop with the improved capabilities enabled by LifeRing.


Team's Location


Team's Occupation


Team Members

Adam Owens, Guy Walker, Chris Bellamy, Harry Blandy

Focus Area(s)

Alert/Response, Diagnosis/Treatment/Referral, Behavior Change, Data Collection/Data Insight

UNICEF Pillar(s)

Health, Water, Sanitation and Hygiene (WASH), Child Protection, Nutrition

These pages have been pulled directly from applications submitted to the Wearables for Good Challenge in 2015. They represent the work of the individual teams and have subsequently not been edited.


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