My Final Project

Slide and Presentation

Since the beginning of the year 2023, I am working in the field of quantum sensor technology. The goal of our Quantum Technology FabLab working group https://hrw-fablab.de/de/unser-fablab/projekte/quantum-technology-fablab/ and our cooperation partners is to construct inexpensive quantum sensors, which can be used for education, research and as industrial sensor. These sensors can be used to measure very fine magnetic fields, for example. For the measurement, a green laser is directed onto a very small diamond with NV centres. In a NV centre, one of the carbon atoms in the diamond crystal lattice is exchanged for a nitrogen atom and a carbon atom adjacent to the nitrogen atom is missing. This causes the diamond to glow red, when irradiated with green light. The intensity of the glow depends, among other things, on surrounding magnetic fields. The stronger the magnetic fields near the diamond, the weaker the glow. To build such a quantum sensor, it is necessary to align a suitable diamond very precisely in the beam path of the laser. For this purpose, I will construct a very accurate and automatically adjustable xy-table as my final project in the FabAcademy. This table could also be used to measure magnetic fields in 2D using the quantum sensor or to build a scanning laser microscope and much more. I decided to build the xy-table by using a reliant mechanism, since it combines the x and y motion in one layer.

To design a reliant mechanism I tried out serveral geometries (see image below) and finaly desigened my own one. The reliant part ot the mechanism is only one 3D path (0.38 mm) thick, so this seems to be the smallest geometry for a reliant mechanism, which can be printed with a FDM 3D printer. The reliant mechanism is 48x48 mm large and has a compatible large radius of movement of 5x5 mm. I use this mechanism twich in my setup. Once to automatically move the diamond in the focus of the laser, and once to move the photodiode manually in the focus of the second lens. The motorized reliant mechanism is powered by two 28byj-48 stepper motors. The shafs are coupled to headless M5 screws. These are threaded in hexagonal long nuts. The long nuts reach in hexagonal holes in the reliant mechanism. This prevents the long nut from turning, so it is forced to move forwards or backwards, when the stepper motor is rotating.

Here you can see most of my 3d prints of the reliant mechanism in my journey to optimise it:

And here you can see the final reliant mechanism. One stepper motor driver is attached, the other not the show the mechanism of the linear guidance. Later I attached the drivers to the back side of the reliant mechanmis.

In the square-shaped middel of the reliant mechanism a transparent pcb foil with NV-diamands is located. The dimonds are glued to the foil using superglue. The foil is attached to the reliant mechanism with tiny glasses and watch screws. The reliant mechanism moves the diamonds in x- and y- direction in a serpentine-like movement. Acutally the stepper motor for the x-axis makes 10 steps, then the motor for the y-axis makes one step and the motor for the x-axis makes 10 steps back. This process is done till the reliant mechanism moved to 100 different positions. At every position the fluorescent intensity of the diamonds will be measured. By this procedure a adjustment of the diamand to the laser can be found. Later I will try to programm another algorithms, with which a good adjustment can be found faster. The 28byj-48 stepper motors have a high translation of 4096 steps per revolution, which is good for accurateness, but the process to move to 100 positions needs about 8 minutes.

I optimised the reliant mechanism to print it on a bambu 3d printer. For other pinters you probalby need to adjust the geometry. It is important, that the flexible parts of the mechanism are securly attached to the rest of the mechanism. This is the case, when the printer does not start the extrusion at one of the ends of the flexible parts of the reliant mechanis, but earlier and later. In the following image you can see, that the white points (start and end points of the extrusion) are not located at the ends of the flexible parts:

So the one path thick flex part is securly bonded to the rest of the geometry. You can have an influence on this parameter by editing the seam position in Bambu studio. Below you can download the G-codes to print the reliant mechanisms on a bambu printer.
Further, I designed a planitary holder for a green laser to adjust the laser beam to the middle of the reliant mechanism. The two holder, which hold the ball in the middle in place, are fixed with 4 screws and springs, which allow to rotate the laser in the holder.

The lenses are hold in place by holders made of two parts, which can be screwed together. A red filter is attached to a simple flat holder by tape. These parts are inserted into two 96x48x48 mm large cubes and hold in place by lego rods. With the help of adapters the reliant mechanisms are attached to the cubes also using the rods. At the second end of the motorized reliant mechanism a holder for a melt-in thread is attached. In the thread a screw is inserted, at which end a magnet is attached. By this mechanism the magnet can be approached to the diamand.

I desigened the pcbs for my final using EasyEDA. I used a RP2040-Zero microcontroller, because I needed several pins and wanted to fit the pcbs to the size of the cubes with 48x48 mm. This was not the best choise, because many Arduino libraries are not compatible to this microcontroller. So I had to try out several libraries to get things to work. Beside from the µC the pcb contain an analog digital converter, a step down converter to supply the laser with a voltage of 3V, a USB conector to power the µC, the stepper motors and the laser, a display to show the readings of the photosensor and several pins to connect everything.

Then I milled the pcbs with our LPKF-mill. The following image shows the main pcb for the surface mountable RP2040-Zero.

Here you see both pcbs mounted from top:

And from the bottom:

I should have milled a total rubout instead of a partial rubout, then the soldering would have been a lot easier! With the usage of the flux called "Löthonig" I could prevent shorts in my circuits, but the result looks quite messy.

Then I wrote the code in Arduino for the stepper motors, the sensor and the display. In the following video you see the value of the photosensor shown on the display.

Here you see the originally ideas to design the reliant mechanism for the xy-table:

In week 2 I designed the first ideas of the reliant mechanisms:
https://fabacademy.org/2023/labs/bottrop/students/michael-bennemann/assignments/week2_ComputerAidedDesign.html

Downloads

The following files you can use under the Creative Commons-Licence: CC BY-ND 4.0

Please cite: © Dr. Michael Bennemann

Reliant Mechanism (motorized)

G-code motorized Reliant mechanism

hand driven Reliant Mechanism

G-code hand driven Reliant Mechanism

endarkenment 48x48 mm with holes

endarkenment 48x48 mm

endarkenment 48x96 mm

endarkenment 96x96 mm

adapter Reliant Mechanism

96x48x48 mm cube © Lena Hangenauer & Dr. Michael Bennemann

ODMR_nurSchrittm_rp2040zero_for2_alleSchleifen_tut2_9_10_II

All 3D geometries were designed by myself except for the magnet mount and the red filter mount, which had been designed earlier (see copyrights above). Also a 48x48x48 mm large version of the cube has been designed earlier in the Morph3Dbot project - the final FabAcademy project of Lena Hagenauer.

Materials

Qty	Description	Price	Link
1	diamonds with NV-centres (MDNV150umHi30mg)	$382 plus shipping, handling fee and duty	https://www.adamasnano.com/fluorescent-agents/
4	linear drive (not used)	9.16 €	https://de.aliexpress.com/item/4000406385009.html?spm=a2g0o.order_list.order_list_main.83.47fb5c5fwgcCt6&gatewayAdapt=glo2deu
2	xy-table (not used)	2.35 €	https://de.aliexpress.com/item/32972295033.html?spm=a2g0o.order_list.order_list_main.142.47fb5c5fwgcCt6&gatewayAdapt=glo2deu
1	USB-C Port	0.29 €	https://de.aliexpress.com/item/1005005747511572.html?spm=a2g0o.order_list.order_list_main.12.4b465c5fjtiCqZ&gatewayAdapt=glo2deu
2	limit switch	1.15 € each	https://de.aliexpress.com/item/1005003536527857.html?spm=a2g0o.order_list.order_list_main.49.4b465c5fjtiCqZ&gatewayAdapt=glo2deu
1	photosensor	2.30€	https://de.aliexpress.com/item/1005004743918321.html?spm=a2g0o.order_list.order_list_main.55.4b465c5fjtiCqZ&gatewayAdapt=glo2deu
2	springs (0.4mm, 6mm, 20mm)	2.35€	https://de.aliexpress.com/item/1005003389383775.html?spm=a2g0o.order_detail.order_detail_item.19.4a8e6368wjTpws&gatewayAdapt=glo2deu
1	RP2040-Zero	2.41€	https://de.aliexpress.com/item/1005004389234434.html?spm=a2g0o.order_list.order_list_main.75.4b465c5fjtiCqZ&gatewayAdapt=glo2deu
1	step down converter (3V)	2.35€	https://de.aliexpress.com/item/32810850343.html?spm=a2g0o.order_list.order_list_main.92.4b465c5fjtiCqZ&gatewayAdapt=glo2deu
4	lego rod (U20-1x32 10PCS)	3.34€	https://de.aliexpress.com/item/1005003224783056.html?spm=a2g0o.order_list.order_list_main.96.4b465c5fjtiCqZ&gatewayAdapt=glo2deu
2	coupler (5mm-5mm)	0.26 € each	https://de.aliexpress.com/item/1005003808341565.html?spm=a2g0o.order_list.order_list_main.250.4b465c5fjtiCqZ&gatewayAdapt=glo2deu
1	display	15.99 € for 3	https://www.amazon.de/gp/product/B074N9VLZX/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
2	long nut (20X M5x30)	6.29 €	https://www.amazon.de/dp/B081M2GFHV?psc=1&ref=ppx_yo2ov_dt_b_product_details
2	headless screw (M5x40 - (10 Stück))	3.65 €	https://www.amazon.de/dp/B077XRMBRR?ref=ppx_yo2ov_dt_b_product_details&th=1
1	glue	19.99 for 3	https://www.amazon.de/Alleskleber-MaxRepair-transp-UHU-ExtremKleber/dp/B01481O9KS/ref=sr_1_6?crid=2PJPNPD17SOD9&keywords=uhu+max+repair+extreme&qid=1699734506&sprefix=uhu+max%2Caps%2C89&sr=8-6
1	laser (532 nm, 1 mW,	37.20 €	http://www.roithner-laser.com/laser_modules_dot_532.html
2	stepper motor	1.72 €	https://de.aliexpress.com/item/32714267741.html?spm=a2g0o.order_list.order_list_main.464.4b465c5fjtiCqZ&gatewayAdapt=glo2deu
1	red filter	6.99 €	https://www.amazon.de/DECARETA-Farbfolien-Farbfilter-Transparente-Fotografie/dp/B0C5J4NR2N/ref=dp_prsubs_sccl_1/261-7272380-4118516?pd_rd_w=jCf6W&content-id=amzn1.sym.760655e3-a281-472e-9463-2bddd33448c0&pf_rd_p=760655e3-a281-472e-9463-2bddd33448c0&pf_rd_r=SYP9KZ21XA2SEC54FSNT&pd_rd_wg=8iwKn&pd_rd_r=4804762a-0d80-4a20-827c-58e1e7913f0e&pd_rd_i=B0C5J4NR2N&psc=1
1	melt-in thread (length 12mm, 25pcs M4 (OD 7mm)	4.03 €	https://de.aliexpress.com/item/4000585933306.html?spm=a2g0o.order_list.order_list_main.587.31335c5fTMRGOq&gatewayAdapt=glo2deu
1	lenses for VR glasses (25 mm)	4.57 €	https://www.amazon.de/FASOLI-Linsenf%C3%B6rmige-bikonvexe-Acryllinse-virtuelle/dp/B0C4YBV5LB/ref=sr_1_6?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=244SRRIOSBBA3&keywords=linsen+f%C3%BCr+vr+brille+25mm&qid=1699782818&sprefix=linsen+f%C3%BCr+vr+brille+25mm%2Caps%2C73&sr=8-6
8	glasses and watch screws	5.07 €	https://de.aliexpress.com/item/1005004744859993.html?spm=a2g0o.productlist.main.3.241647eezmuCbl&algo_pvid=5f1e3e54-811e-4154-8b9c-f6b43f4b94a8&algo_exp_id=5f1e3e54-811e-4154-8b9c-f6b43f4b94a8-1&pdp_npi=4%40dis%21EUR%2110.35%215.07%21%21%2110.79%21%21%402103893b16997982535002854e4abc%2112000030317297163%21sea%21DE%212600609762%21&curPageLogUid=407OJVKXV6uV

If you have any questions to my final project feel free to contact me: michael(dot)bennemann[at]hrw-fablab{dot}de

The idea of this kind of quantum sensors is already published: Jan Stegemann et al 2023 Eur. J. Phys. 44 035402 https://iopscience.iop.org/article/10.1088/1361-6404/acbe7c