Possible to Design a Mini Printing Device Like This -- Mechanical-Wise?

Why not just send it to your printer....or E-mail it to yourself...or take a picture....or do a screen capture...they do have magic wand scanners and small portable wireless bluetooth receipt printers...

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=wireless+printers+small+portable&rh=i%3Aaps%2Ck%3Awireless+printers+small+portable

So did I, but I seem to stumble on a smartass every now and then, who doesn't have a clue....

You occasionally stumble across one now and then? Yo umust be a fleet of foot as a world class ballerina or olympic figure skater!

I'm tripping over them everywhere I go all day every day.

Cripes they're even in my mirrors too.

You don't need a printer at all. You need a pencil or ball-point pen. Instant result and far cheaper.

And with carbon or NCR paper you can make multiple copies with little added energy! - JHF

Something like that could be done. However, the trend is definitely toward paperless and away from printed paper.

My experience: About a year ago I started working as a contract project engineer at a factory where I worked from 1995 through 2001. Same plant, same job, 2 different owners, both Fortune 500. When I was there the first time, most everything was paper - drawings, proposals, contract work descriptions, quotes, purchase orders, etc. My mail folder was filled with this and approval documents each day.

Now, about the only paper is construction drawings. All that other stuff is handled electronically. Each month, I get an e-mail from IT stating my printer usage, B&W, color, 1 or 2-sided, and comparing it to my 'peer group.' Color and 1-sided are discouraged and the printer defaults are 2-sided, B&W (over-rides the saved document settings). I print, on average, 2 to 3 pages per day. And, I have not received one piece of paper mail in my mail folder - in over a year! (I have had maybe a half-dozen pieces hand-delivered.)

If I were following your trail, I think I'd abandon the 'pocket size' and go with something closer to this (that's a Neat portable scanner):

Replace the scan head with a print head and you're good to go. (That print head might be your biggest challenge.) If you're going to be carrying a notebook anyway, you might as well incorporate the printer into it. You could include loops to attach it with the notebook rings, or make a notebook with the printer built-in. Either way, a blank sheet of paper could be fed manually.

There might be a niche market, but you are definitely swimming upstream on this one.

This is a great idea!

I suggest that you contact Rube Goldberg. Just search the internet for his company.

He will help you.

See the movie "Allegro Non Troppo"

I think it's hands-down the rat!

What you ask for does sound like your complicating it more than it should....

but what you ask,sounds like what they use to call PDA's. But now with the apps available, you can take notes on your tablet and do it.

I have to ask this question, did you check to see what's already out there? If you did, can you refine your intent more.

Is this what you're looking for?

Amazon's got everything.

Amazon's got everything.
Portable printing in an environment that's headed in a paperless direction? That just BEGS for a RS232-C shredder. You don't have to print the info to paper and then mechanically shred it. Save paper, save ink, save time, save wear-and-tear on the printer. Shred the data prior to printing, with the RS232-C shredder.
Save disposal costs. Avoid polluting the environment with the decomposition products of ink.

How come I couldn't find one on Amazon? This is a golden companion business opportunity for the OP to pursue.

Hand held printers with about 2,600,000 results in 0.40 seconds. Next .....

To hell with the patents go for it, buy one and try reverse engineering it like China everyday.