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4.2″ and 7.5″ NFC-powered e-Paper Displays Work without Battery (cnx-software.com)
770 points by homarp 7 months ago | hide | past | favorite | 146 comments

This could replace your printer really nicely. Anytime you want to print something out, you swipe your phone by this and use it instead.

Any kind of reference, recipe, directions, notes. This would even be cool instead of a second monitor. Just to put up a reference page or cheat sheet.

It's nice as long as your document fits on a single page. Otherwise you need several of them, and it won't allow you to scribble on it or highlight stuff.

IMO this is still less functional than an ordinary sheet of paper, this just solve the energy issue, but not much else.

I'd still probably go with a powered one just to get the benefit of swapping pages and taking notes on it.

On the other hand, if the can manage to make something that can power them over a longer distance than typical NFC, I could see those used for in-office digital signage (meeting room status and schedule, employee schedule, etc) which doesn't require a battery swap, PoE or some other kind of way to power it.

Now I understand why the Stark Trek people used to have dozens of tablets ;-)

The pricing should also play a significant role in its adoption. Especially if unbundled with other phones. At almost $42 and $70 (for the larger display) we should wait to see which subset of customers could justify it's use-case in daily life.

Did you forget an extra zero or are they really this cheap?

Yeah I had to do a double take. It's less than $80 before shipping.


They're also for sale on Amazon for about the same prices.

Price tags, menus, or e.g. corporate announcements is the only thing I can think of really, but I'm not the most creative.

I've seen a system like this used for price tags already at one of my previous jobs. The tags were e-ink displays that were updated wirelessly using a special tool.

Such tags have been used for years here in northern European supermarkets. Not sure how similar they really are though.

The resolution is only 800x480. What reference page or cheat sheet would fit on that?

You used to be able to stick a lot of text on a 320x200 display when I first got into software development. :)

Jokes aside, you'd probably want that 480x800 (portrait rather than landscape). Which would be 80 columns and 100 rows in old 8-bit microcomputer terms. So it wouldn't be the more detailed of a document but it should be detailed enough for a cheat sheet or narrowly focused reference page. You probably wouldn't want much more than that anyway otherwise you risk your reference material to be too verbose for quick sanity checks.

I'm always surprised that e-ink readers have such good readability at low resolutions. I think an accidental by-product of how they work is a little "fuzziness" when translating from digital data to analog atoms, so the text looks more like organic newspaper ink than a pixellated screen.

Anyway, most e-readers are in the ballpark of 800x600; and I expect if the concept got traction, there's no reason it couldn't be scaled up to 8.5" x 11" at equivalent pixel densities (at the cost of hovering your phone for a few seconds longer or whatever).

> Anyway, most e-readers are in the ballpark of 800x600

A Kindle Paperwhite is 1072x1448, 300 PPI, 16 levels of grayscale.

I personally couldn't tolerate reading on a kindle until they reached 212 PPI. 800x600 may be acceptable for a simple sign, but it's not gonna wow anyone.

I think you must be spoiled by modern high-dpi displays if you can't see any use for 800x480 displays. When I was in school I used to put cheatsheets on my TI-83+ which had a 96×64 monochrome display!

Isn't that the same as the OG Kindle? If so, you can fit approx half an A4 / Letter page at adequate readability.

Lots of useful things would fit on that, and resolution increases with technological refinement.

If you swipe two phones, you can double the resolution.

I currently do something like this with a cheap thermal printer. Aside from apparent environmental issues of thermal paper, it is really great to print out these short, portable, and disposable materials on a whim from my phone (Bluetooth) and computer (USB).

The reactant in thermal paper is often BPA.

Might pay to check yours and read the health effects section here https://en.wikipedia.org/wiki/Bisphenol_A

Edit: fixed a word

Couldn't tell but is BPA toxic on skin contact. All the worry I was hearing was based on ingestion.

saurik 7 months ago [flagged]

Do a Google search for "BPA toxic skin contact" (search terms you came up with) and be amazed at the wonder of modern search engines (which will return results from PubMed, Nature, and WebMD).

(edit) There is something telling about how three people have now downvoted my comment for not doing the work of pasting the links myself, but not a single person has bothered to provide the links themselves, which kind of demonstrates the problem with these comments: the comment I am responding to is undermining a well-researched notion--one that AFAIK no one questions, and for which it is trivial to find numerous articles and studies: that BPA is absorbed through the skin from receipts--with the moral equivalent of "citation needed"; that comment asking for a reference seriously took longer to type than finding the relevant articles would have, and yet in practice is asking other people to do that work, and so the work doesn't get done by anyone... but the comment itself sits there, making people who are less informed on the topic question the validity, as in "I dunno, this comment claims they hadn't heard that, and is demanding citations; if it were easy to find a citation they wouldn't be asking that, so I guess the thing they are poking at isn't actually true". If you want to downvote my response to that behavior--which is to point out that a Google search would have worked--but you aren't willing to actually do the work of providing the links yourself (or at least also downvoting the comment), you are just making yourself part of the problem of incentivizing leaving these misinformative comments :/.

I say this to be helpful, so please don’t take it as an attack. While initial comment added no value (e.g. that Google exists), but what I found off-putting was your tone. That, coupled with the comment[0] in your profile, make it easy to jump to a specific conclusion, right or wrong, about your intent. just be mindful of perception. FWIW, I struggle with this daily and often wish more folks would point out when I’m coming across in a way I didn’t intend.

[0] “I make it something of a policy to not look at things people say in response until at least a month later.”

You are being downvoted for being snarky, which is against the HN guidelines.

You are being downvoted for commenting on voting, which is against the HN guidelines.

Commenting on downvotes is against guidelines, while commenting on commenting on downvotes is ok: that's how word gets out not to do this.

Commenting on commenting on commenting on downvotes, which you're doing, is annoying. I'm on an even number here, so I should be okay. We'll see!

> The reactant in thermal paper is often BPA.

Too bad. The original "invisible ink" activated by heat is lemon juice.

I heard this before, but how does that knowledge help with dealing with BPA exposure now?

Obviously, it doesn't. But the knowledge of lemon juice is something you can pressure your thermal printer vendor with.

Or milk.

The only times i use a printer these days if someone else wants me to deliver something on paper, not for myself. ePaper is just as unacceptable as digital on phone. Last time was to have a paper copy of a india e-visa.

These type of E Ink devices takes seconds to update

I don’t mind. Printers often have a startup time of multiple minutes. And with printers we waste paper and we are required to refill them with ink or toner.

I will gladly use this e-Paper display instead in any situation where I want some kind of reference sheet like the parent commenter said, and where the resolution is sufficient.

Refresh time is listed as 4 or 5 seconds, depending on how big the display is.

But no color, and no real gray scale.

You can simulate grayscale with dithering, similar to drawing with a pen or pencil. If you really need grayscale or color you can buy eink displays that support it, even ones up to 300ppi. I don't know if 1w would be enough to power them though, and they're a bit more expensive.

Considering these types of displays don't require active energy input to function, I don't see why you couldn't update any size display with 1W. You'd need to progressively update parts of the display at a time, which likely requires extra engineering effort, but in theory it should work.

Would be interesting for use on a boat. Generally you want a fast refresh rate but once a minute would be fast enough for most users. The problem with navigation displays on boat are

1. daytime visibility 2. long term waterproofing in a saltwater environment

With this setup you could mount a raspberry pi W on one side of the fiberglass to interpet NEMA 2000/0183 data and the NFC chip, and the waterproof, hermetically sealed e-ink display on the other, held on with velcro or neodymium magnets etc.

I've gone through multiple RPi on my boat. Maybe if I epoxied the board it would have a chance.

Most epoxy isn't very flexible, and cracks leading to leaks over time.

For something you can do at home, try heating the whole thing to 120C and dipping in hot glue.

Idk about new hot glue, but I have some old projects with hot glue from about 15 years ago and it's starting to dry out and crack. Something to keep in mind if looking for longer term.

With this solution you could never be sure that pi is functional and displayed data is fresh - you'd have to always compare display clock with wrist watch or something.

It would be a good choice to replace tablets that are used outside conference rooms to show the schedule and/or book the room.

If you could parasitically power the unit from Wi-Fi beacon frames that would be awesome. The idea of a sign that "magically" updates itself over the air gives me a giddy "I live in the future" feeling.

Actually, there are units similar to this that update over Infrared (even non-directionally)

Best Buy use them as price tags: https://www.youtube.com/watch?v=7aVoeDC-7MA

Similar insofar as using e-ink, but they're battery operated (from what I can tell). The "coolness" of what I'm talking about would come from being a completely passively-powered device.

The power density of light is vastly higher than the power density of Wi-Fi almost anywhere. If you can't do it with PV, you definitely can't do it with Wi-Fi.

WiFi -> electric current rectennas announced a year ago[1] were in the range of 40 microwatts, and the blog post says this NFC system runs at 1.4 Watts, that feels a long way away. But years ago LCD calculators could run on a solar cell the size of a finger and powered by ambient room lighting - surely must be some close to crossover level available.

[1] http://news.mit.edu/2019/converting-wi-fi-signals-electricit...

I'm wondering if that was a constant 40 microwatts, and if that could be stored in capacitors so that every 4-5 seconds (the refresh rate of the panel) there would be enough energy accumulated to power the circuitry for an update.

Yes is the answer, but it would be much slower. Assuming 1w for 6 seconds (4s refresh + 2s transfer), it would take about 42 hours for a lossless storage + regulator circuit. 40uw is an incredibly small amount of power.

It doesn't say that the e-Paper requires 1.4 Watts. The board that can be used as an alternative to a mobile device provides 1.4 Watts.

Interesting thought. At that point (or for that fact - at this point) it's is essentially a reusable printable paper. For people arguing about the low resolution of the $70~ model, I would not disregard their argument because we haven't seen it in real life and would love to see how documents scale up on that display.

If you aren't using super-white printer paper, not sure that this is any more eco friendly than printing a sheet of paper off twice a day, every weekday for years. Not sure what the materials impact is for e-ink, and paper is a renewable resource and sourced from trees generally grown specifically making paper as a crop.

We already power our iPads via POE< which is also how you'd power those beacons, so it's not really a great improvement.

BUT the idea that you would "tap in" to book it would be great.

I'm talking about radio energy powering the device. 802.1 beacon radio frames, which your access points send out over the air. Configure it via USB, etc, then just hang it on the wall. No cables. Just a passive device.

Is there a PoE to lightning adapter?

edit: $28 splitter, https://www.poetexas.com/products/af-lightning

And $100 Belkin Ethernet-PoE adapter.

Use a PoE to USB (female USB-A or USB-C) adapter - variety of models e.g. I saw one for $10 on Alibaba.

My employer uses Roomz (https://roomz.io/) which does exactly that.

It has some trade-offs like being very laggy if a meeting is spontaneously cancelled, and it doesn't show double bookings, but besides that, it's pretty attractive.

They're battery powered:

> More than 2 years of autonomy for the ROOMZ Display and more than 4 years for the ROOMZ Sensors. Runs on single Batteries that can easily be replaced.

Still, 2 years is pretty good.

I've seen companies waste some pretty serious time on admin and maintenance of room reservation screens by the doors. Oddly enough they had chose not to go with an iPad based system because of cost

My university replaced some room reservation tablets with pieces of paper on a clipboard.

what were the reasons for doing so? maintenance, theft/vandalism, or worse, bad software?

I assume there was some maintenance cost, but the biggest problem I saw with the tablets was there was nothing preventing anyone from deleting somebody else's meeting and replacing it with their own. There was authentication on the web interface, but nothing if you just directly edited the schedule on the tablet.

At least with the paper-on-clipboard, it's obvious if an existing meeting was crossed out.

The enterprise systems tie in to your Exchange / Outlook messaging for shared calendars. We saw excessive equipment failures with the Steelcase line. This was a few years ago. But like I said, they had the option of using iPads, but went with the proprietary solution instead -- which was NOT reliable for deployment.

With such limited power budget, is there any security circuits for authentication and encryption?

If not, it would be super easy hack.

Most signs are completely insecure already. This exact tech, with no security, is already used for item/price displays in some stores. If you're worried about someone walking up and reprogramming your nfc powered eink sign, I'd love to hear why you need a secure but wirelessy powered sign.

Even the most basic xor "encryption" would use virtually no power. Define a key and xor all data coming in with it. Given the slow refresh rate of these things, it would provide sufficient security against a bruteforce.

Upload a file consisting of all zeroes (or any other known content for that matter) and now the contents of the screen is the secret used to XOR the input. Surely you meant something a bit more substantial?

You can check for a magic string after decryption and only update the screen if valid.

At this point you might as well just require a plaintext password to update the screen, and forget the XOR.

My employer and university have had these on conference/lefture rooms for years. They're ridiculously expensive from what I remember (700€ for the ones at work, I think, the uni ones are larger and older, so probably even more expensive), but compared with not getting the information as easily as they provide it makes them worth it.

$70 for the larger one, I was really surprised at the low cost.

getting larger and the ads displayed in store windows could eventually be replaced. it would be a much better way to display pricing and menus in restaurants than the current fad of large monitors.

there are all sorts of places where information does not need real time updates that this type of technology could eventually satisfy. the best part is reduced energy use and even paper use

Many of the grocery stores in my area actually use e-ink labels[0] on the shelves.

[0]: https://www.displaydata.com/

Open source code to write the image using libnfc and node.js 8.x: https://gitlab.com/bettse/wne_writer

Does it not work with standard NFC libraries?

Like contactless payments, it uses NFC (the protocol), not NDEF (the data format) to write the image. You're not writing the image as an NDEF message, so NDEF-only systems (like early iOS support or WebNFC) won't be useful.

Many people on this thread are complaining about the poor performance of this passively powered screen. PSA if you care about resolution and speed, and don't mind powering it; pick up the ED060KC1 panel. 300ppi 6" panel for around $75, base refresh is 450ms. If you're brave, it seems mostly stable down to 300-350ms. It's the same panel most high end ereaders use.

If you want the same "NFC updating from an app" ability, a small solar panel, enough to charge a supercap, so you have enough energy to update the screen once per few hours could be the solution. You can still use the NFC power option, just wait longer if you need more frequent refreshes.

when I looked it up I was finding listings for at least $150, what sellers are you getting the $75 estimate from?

Aliexpress/eBay market prices. You can even get them cheaper than that, it's just that $75 is more available.


Same question here! The cost of these panels for like anyone whos' not a major manufacturer to use is so high it seems. I just wanna make some fun prototypes ya know.


"e-Paper displays have great readability under sunlight, and only consume power when updated. But their refresh rate is limited, and most displays are fairly expensive."

I've been searching for a tiny computer / screen combination that would work under absolute minimal power; that is, if you were in deep space (or in the deep wilderness), and only had a small (say, 5W or less) solar panel for power, then what tiny computer / screen / keyboard combination would you use?

Well, this screen seems like it might be ideally suited to be the screen component of a setup like that...

I had one of these back in the mid-90s: https://en.m.wikipedia.org/wiki/Poqet_PC

It did a lot of trickery, like suspending the CPU between keystrokes, to get a weeks “work” (I was 12) out of it running on two AA batteries.

Jailbreak a kindle. They are super low power and cheap with lots of features - I’m guessing a 5W solar panel would be overkill if you only update the screen irregularly.

On that note... The remarkable sipposidly allows access for writing software (I think their dev documentation leaves something to desired..). Might also be an option.

Ed: https://remarkable.engineering/

Or better yet, get an Android tablet with an eInk screen. Power consumption will be greater, but assuming the screen isn't refreshed constantly, 5W should still be enough to keep it going.

Came here to say this. I've been playing with doing some development on one, but the kernel must be really old now. Do you happen to know whether there's a way to update it?

Also consider Kobo devices which may be slightly more hackable.

I'd want to check this before committing, but my understanding is that e-ink is cheap power-wise because it doesn't require power to maintain the image - actually changing the image, though, is more expensive than LCDs or OLEDs, so if you try to, say, watch a video on an e-ink screen, you're going to get worse energy draw than an LCD display.

Also this is 0.2fps. (or 0.25fps for the smaller one).

Could also try a Sharp Memory LCD. Faster refresh rates and pretty low power consumption depending on usage pattern. Here's an article of someone using it with an ESP32: https://hackaday.com/2020/01/07/how-low-can-an-esp32-go/

I've had one of these for a few months, and its pretty awesome to be honest:


You can do surprisingly much with today's electronics even on a tight power budget. E.g. Pi Zero W can operate on ~2.5 W. The remaining power can drive a much larger e-Ink screen, or even a small TFT.

If this can be made thin and small enough, it'd be cool to use it to put your remaining balance and perhaps recent transactions on transit cards.

Let's talk that through a bit more.

I wonder if it could be used to create one-off cryptographic notes - that, when used (scanned), are somehow deleted and can never be used again.

Can't think of a way off the top of my head, but I wonder.


Already used to make dynamic CVV codes for cards which change every 30 minutes.

That’s cool

If the encryption is strong enough, you could assign a subset of predetermined keys to each card issued-- but you still need a robust server/network to verify the transaction ACID-style & invalidate the key (or part of the subset?) at the end while retaining the rollback ability until that final invalidation is verified.

Tricky business, for sure. Seems theoretically plausible, but I'm sure there are many things I haven't thought of.

If I worked at Waveshare, I'd partner up with a phone case manufacturer and sell user-customisable phone cases.

They could also offer a SDK so apps could publish high utility info with low update frequency on the case itself: weather, public transport realtime schedules, etc.

(Edit: had originally written "low-latency" instead of "with low update frequency", because of the strong conditioning to associate "low latency == good")

I'd love to see something like this on hard drives, both bare ones and ones with enclosures.

Seems to be a bit thick for a case at 1cm thickness [1] + it would probably need a screen protector itself.

1- https://i.imgur.com/dY1YHkU.png

Yes, for now it is, but it's also stacked so it looks like it's "all screen". Maybe if you could spread components around, it could be thinner.

Somebody else commented this: https://www.gemalto.com/financial/cards/payments/dynamic-cod... I suppose if you can fit it inside of a credit card it would fit a case, and it would be really cool.

Oh, I wish it came with a USB NFC device so I could send it an image from my desktop. Not sure what I'd use it for, but at that price point I can figure something out :-)

I've always been highly annoyed that I cannot set the screensaver on my Kindle to "the last page I read". Then I would set it to things like my itinerary when I travel, to an editor cheat sheet when I'm learning an editor, etc.

I think Chrome 81 has WebNFC too https://googlechrome.github.io/samples/web-nfc/

Yes, but this particular board uses the low-level i/o that are mentioned as not supported.

That said, IF the board firmware was open, you could probably get it to speak NDEF if you were willing...

Clicking "Read More" on the cookie banner sends you to Google for "How to remove cookies."

No, I want to set a cookie to tell y'all not to set tracking cookies and just limit it to strictly necessary ones.

I can remove them and their server will go ahead and set them again.

And no, sending me to a property owned by one of the worst offenders in this space is not what I want.

These look similar to the ePaper price tags I've seen starting to pop up

I wonder if the same app will allow updating those.

I would hope that electronic price tags make use of some sort of authentication in order to set the price that they display.

In Norway, where I live, big retailers will often allow you to pay the price that is shown on the shelf even if their cash register is returning a different, higher price.

I have personally experienced a difference between shelf price and cash register price a few times, and in all of the cases where this happened at a big retailer they allowed me to pay the shelf price.

I actually thought that they were required to do this by law, but looking into it now I find that it is only a recommendation that they do so and not something that they are required to do by law.

The Norwegian Consumer Ombudsman (the government-appointed ombudsman in Norway for consumer affairs [1]) has an article on their website about this topic [2]. Translated from Norwegian, here is an exceprept of what they say:

> * Do you have the right to buy the item at the price at which the item was marked? The Marketing Act does not grant such rights, and it is disputed to the extent that one has a legal right on other grounds to demand the purchase of the item at the shelf price.

> * The stores should still allow the customer to pay a shelf price. It is the store that made the mistake, and it would be very bad service to allow for this to negatively affect the customer who notifies them of the error so that they can correct it.

Anyway, as mentioned you will often be allowed to pay the shelf price rather than the cash register price when you're at one of the stores of the larger retailers. So obviously it would be bad for their business if someone was able to manipulate the price tags without them noticing it.

In closing I should also note that there are probably limitations to how big of a difference in price that they would be willing to accept. In my case it has often been a matter of $20 in difference at most. So, don't expect that you would be able to pay like $99.50 for something that was supposed to cost $995 or anything like that, even if the shelf price somehow ended up showing $99.50 :P

And also, any consumer that changed the price-tags of the things they were buying in order to con the store into selling it to them at a lower price would see no sympathy from me when they inevitably eventually got caught for doing so. Remember, kids: Just 'cause it's technically possible don't mean you are legally allowed to do it. If you notice a vulnerability in a system I strongly recommend that you don't touch it and that you at most let them know about it anonymously unless you have prior written consent to investigate and/or mess with the electronic systems that belong to other people, businesses or other kinds of entities.

[1]: https://en.wikipedia.org/wiki/Norwegian_Consumer_Ombudsman

[2]: https://www.forbrukertilsynet.no/regler-for-prismerking-buti...

Wow, this looks wonderful! It reminds me of my old solar-powered Casio calculator. I have a Boogie Board already, but I can see how computer access can change the game (accurate drawings, NFC to save, etc.). Hope to see these guys around more!

Oh that's great. I wanted a nice, updatable eink screen for things like "this weeks recipies" and have been trying to work out how to drive it / power it without spending too much. A jailbroken kindle and a server somewhere could work nicely, but there's a lot to that and I don't really want to spend too much time maintaining things.

Would be interesting to know if people have got it working with other NFC apps / how hard it is to add to your own app.

I'd be happy with just taking a screenshot of the recipe and scanning it on to the e-ink - this will save my phone quite a few run ins with oily/dirty hands while cooking.

My phone screen locks quickly and uses a long PIN so it's terrible for recipes. I've been trying to think of a cheap simple alternative.

This is really excellent. Various projects I've wanted to do with old iPads all require a power source. Price is a little steep but hopefully lower in the future?

I'm really impressed they've got current requirements down to the level where NFC can power the refresh. Geometry has to be the next step. When eInk busted out of MIT in the late 90's, they kept revisiting flexible formats without too much luck. I hope the flexible screen folks are cross pollenating with the eInk brains. In this example, even though the display is small, the electronics around it are very bulky.

Awesome! I'll be getting a couple of these for my sound studio .. these are the ideal things to use to put up the daily recording schedule/sessions, plus "RECORDING - QUIET PLEASE" type signs.

I've wanted to put an e-ink display up on the door for a while, but always stumbled when it came to actually routing power to the door - but this just elegantly solves the problem completely.

This could be great for a calendar or schedule at work, network a bunch together and push updates whenever needed. Or weather forecasts. Or acting as a live sign for reserving conference rooms, allow people to reserve on a web portal or at the sign. For ~$100 (with a raspi or similar) this competes with whiteboards.

I wonder if you could somehow get this to work with some form of passive wifi, maybe slowly harvest energy from available radio signal to trigger a screen update. Maybe someone knows if this is theoretically possible?

Very cool. I love ideas that seem super obvious after you hear of them.

I wonder what sort of security it has? Wouldn't want anyone to be able to deface it.

The photos make it looks like there's a micro-USB port on the bottom. Any idea what that's for?

Anyone could smash or paint over these if they really wanted to deface them. I'd be more concerned about subtly tampering with the image, e.g. changing a displayed price.

It's far better than a paper sign or label. It'd be much easier to just put a sticker on top of the screen if you wanted to deface it.

AES GCM should take insignificant amounts of power compared to eink panel refresh and make this secure enough (unless there's no way to reprogram the mcus in there?).

Then, just undeface it.

Doesn't help much if the display is in a public place like a supermarket.

I've seen e-ink price tags in grocery stores, and it doesn't seem to be any more of a problem than someone writing over a paper price tag with a Sharpie.

But maybe more of a target?

> micro-USB port

Firmware updates?

Anyone find if the NFC protocol is documented somewhere?

>Anyone find if the NFC protocol is documented somewhere?

You won't probably like this (between 100 and 600 US$ per document):


Posted elsewhere on this discussion: https://gitlab.com/bettse/wne_writer

Just a tad too slow to be a cool e-reader.

Why can't I navigate the world without running across hideous, overly sexualized imagery of women at irrelevant, random times?

If it stinks everywhere you go maybe it's time to look under your shoe.

Dude is some anime fan and boss told him to make a video demonstrating photos so why not take a pic of his anime figure? You're overreacting to say the least.

Not cheap (USD 42) but still cool [0]

[0] https://www.aliexpress.com/item/4000418859190.html

It's roughly 10 US$/inch, and is not that there that many uses for the smaller 4.2" model, the US$ 70 for the 7" model is IMHO more than "not cheap", "rather expensive".

I guess that for the "this week recipe" a more traditional printed paper remains cheaper and more practical.

For "daily" or more frequent need of refresh, maybe it may become a valid choice.

I see at least one good use for the smaller one: Price tags at a supermarket.

Instead of a team of clerks changing the labels for three hours at night, you can have one guy do the whole store in that time. The savings in labor would quickly make up for the initial expense.

E-ink shelf labels are quite common here. NFC in that case seems like a much worse option than longer distance radio communication powered by a small battery lasting a few years.

As the article notes, this is probably best for information that needs to be updated relatively infrequently, if you're doing it so often that labor cost is at all much of a concern. Updating displays one by one manually using NFC seems like it would be nearly as labor intensive as swapping paper labels.

I don't know where you live, but here in France I haven't seen a paper price tag for years. Every chain store has been using e-ink tags for a long time.

Only one of the grocery stores near me uses LCD price tags.

There is a constant hiss/buzz from the power and I presume they aren't OLED because I can see the inconsistent backlight that goes out in places along the strip.

Feels cheap and crappy overall.

Sure, but - all in all - it is not that the batteries will make a difference, if you have to change them - say - once every 1 to 5 years.

Comparable "normal" e-ink labels cost much less than these (like 50-60%) AFAIK.

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