Part 3 · Design

The Thimble Station: device architecture

Status: concept design. Nothing here has been built, verified or cleared. Every performance number is a design target taken from a named precedent, and the business plan says what happens if a target is missed.

In plain English: Instead of one magic machine, the Station combines four kinds of measurement that already work in other products. Each gets its own small share of the blood. The Station checks every sample for problems and refuses to report a number it cannot trust.

The Thimble Station is a counter-top analyzer for pharmacies and urgent care clinics. It runs about 40 assays plus a 19-parameter complete blood count from a capillary sample of roughly 300 microliters, with all in-store results in about 15 minutes, and sends anything it cannot run well to a central "hub" laboratory the same day. It does this with four kinds of measurement engine that have each been cleared or CE-marked by other companies, arranged so that no single engine has to do everything.

1. Requirements

Requirement	Target	Precedent that shows it is possible
Sample	About 300 µL capillary blood (upper arm or fingertip), or venous	BD MiniDraw: 16 to 18 drops for 16 analytes. Tasso+: 200 to 600 µL from the upper arm.
In-store menu	About 40 assays plus a 19-parameter CBC	Piccolo: 31 chemistry analytes. Boditech: dozens of immunoassays. HemoScreen and OLO: 5-part CBC.
Time to result	15 minutes or less for everything run in store	Piccolo 12 min, HemoScreen 6 min, ichroma 3 to 15 min.
Operator	Pharmacy technician after about 2 hours of training; CLIA-waived modules by phase D	11 waived Piccolo discs, Sysmex XW-100 (waived CBC), Afinion and DCA (waived HbA1c), i-STAT CHEM8+.
Accuracy	Inside the CLIA acceptance limits that took effect in 2025, with a sigma metric of 3 or better	A cleared predicate exists for every analyte.
Throughput	3 to 4 patients per hour per Station	One chemistry disc per 12 minutes.
Footprint	Under 0.2 m² of counter, under 15 kg	Piccolo is about 5 kg; Truvian is desktop-computer sized.
Connectivity	HL7 and FHIR results, remote QC, works offline	Piccolo EMR export; Athelas cloud results.

2. Design principles

Split the sample by assay class at the moment of collection. EDTA for cells, lithium heparin for chemistry and immunoassays, serum only when the hub lab needs it.
No new physics. Four engine types, each with a cleared or CE-marked precedent.
Native volumes. Each consumable meters its own sample. No dilution beyond the validated protocol, no robot pipettor.
Measure pre-analytical quality on every sample. Fill, age, clots, hemolysis, lipemia, icterus.
Suppress, never massage. A result the Station cannot stand behind is not reported. The patient is offered a venous draw or the hub lab.
Everything traceable. Lot, calibration, QC status, operator, sample age and interference indices travel with every result.
The long tail goes to the hub. The Station does the high-volume routine menu; specialty tests ride a courier.

3. System overview

System overview. One capillary draw is split into two tubes and run on four bays in about 15 minutes; results and QC go to the cloud, long-tail tests go to the hub lab.

Plain-text version

   PATIENT
     |  upper-arm vacuum collector (300-500 µL)    or    fingertip by trained staff (16-18 drops)
     v
 +----------------------------------- THIMBLE DRAW KIT -----------------------------------+
 |  first drop wiped  ->  [ EDTA microtube ~120 µL ]   [ Li-heparin microtube ~250 µL ]    |
 |                        [ SST microtube ~300 µL, only when hub tests are ordered ]       |
 +----------------------------------------------------------------------------------------+
        | EDTA                      | Li-heparin                         | SST (optional)
        v                           v                                    v
 +---------------------- THIMBLE STATION (counter-top) ----------------------+   +--- HUB LAB ---+
 |  BAY 1  HEME CARD        BAY 2  CHEM DISC          BAY 3  IMMUNO PACK     |   | CAP / CLIA    |
 |  imaging CBC + HbA1c     centrifugal photometry    time-resolved          |   | courier,      |
 |  20 µL, ~5 min           100 µL, ~12 min           fluorescence strips    |   | same day,     |
 |                                                    15 µL each, 10-15 min  |   | long-tail     |
 |  BAY 4 (urgent-care option)  EC CARD: Na K Cl iCa Glu Lac Crea BUN Hct    |   | menu          |
 |                                                                           |   +-------+-------+
 |  pre-analytics: fill | sample age | clots | hemolysis, lipemia, icterus   |           |
 |  CM5 + NPU compute | real-time MCU | NFC lot data | barcode | touchscreen  |           |
 +-------------------------------------+-------------------------------------+           |
                                       | encrypted results + QC records                  |
                                       v                                                 v
                      +---------------------------- THIMBLE CLOUD ----------------------------+
                      | fleet QC (Levey-Jennings, patient moving averages) | remote lockout   |
                      | lab director review | HL7 / FHIR to EHRs | patient app | audit trail  |
                      +-----------------------------------------------------------------------+

4. Collection and the volume budget

The Draw kit is built from components that are already FDA-cleared: a contact-activated safety lancet or an upper-arm vacuum collector (Tasso+ and TAP Micro Select are cleared), and capillary microtubes with dry EDTA and lithium heparin (BD MiniDraw, BD Microtainer or Sarstedt Microvette class). Theranos's nanotainer was cited by FDA as an uncleared Class II device; the lesson is to buy or clear the collection hardware, never to ship it on an exemption.

Collection protocol (CLSI GP42 order of draw for capillary samples): warm the site, let the alcohol dry for 30 seconds, puncture, wipe the first drop, fill EDTA first (to limit platelet clumping), then heparin, then serum if ordered, without squeezing. Invert each tube ten times. Scan the kit barcode, which timestamps the draw.

  COLLECT (one visit)                               USE (typical pharmacy panel)
  ----------------------------------------------    ------------------------------------------------
  EDTA microtube          ~120 µL   ------------->  Heme Card           20 µL (+5 dead)   CBC + HbA1c
                                                    rerun reserve      ~95 µL
  Li-heparin microtube    ~250 µL   ------------->  Chem Disc          100 µL             17 analytes
                                    ------------->  Immuno Pack        15 µL x 3 strips   TSH, hs-CRP, ferritin
                                                    rerun reserve     ~105 µL
  SST microtube (only if ordered) ~300 µL ------->  Hub lab, same-day courier             long-tail menu
  ----------------------------------------------    ------------------------------------------------
  collected: ~370 µL (about 16-18 fingertip drops, or one upper-arm draw)     used in store: ~170 µL

Volume budget for one visit.

Consumable	Tube	Sample	Reports	Time
Heme Card	EDTA	20 µL	CBC (19 parameters) and HbA1c	about 5 min
Chem Disc, Metabolic + Lipid	Li-heparin	100 µL	17 measured analytes, 6 calculated	about 12 min
Chem Disc, Extended	Li-heparin	100 µL	8 measured analytes	about 12 min
Immuno strip (each)	Li-heparin	15 µL	1 analyte	10 to 15 min
EC Card (urgent-care option)	Li-heparin	65 µL	9 analytes	about 2 min
Hub tube	SST	200 to 400 µL	Long-tail menu at the hub lab	same day

Where a typical sample goes

Heme Card
Chem Disc
Immuno strips
Reserve for reruns

Typical pharmacy panel: CBC and HbA1c, metabolic and lipid disc, three immunoassay strips. The Heme Card figure includes 5 µL of dead volume.

Show the data as a table

Tube	Use	Volume (µL)
EDTA tube, ~120 µL	Heme Card	25
EDTA tube, ~120 µL	Reserve	95
Li-heparin tube, ~250 µL	Chem Disc	100
Li-heparin tube, ~250 µL	Immuno, 3 strips	45
Li-heparin tube, ~250 µL	Reserve	105

If both chemistry discs and several strips are ordered, collect about 350 µL of heparin blood instead of 250 µL.

For comparison: Theranos promised more than 200 tests from "a few drops." Truvian's cleared instrument uses a full venous tube. Babson and BD use 16 to 18 drops for their capillary menu and send them to a lab.

5. Engine 1: Heme Card (imaging hematology plus HbA1c)

Precedents: Sight OLO (fingerstick CBC, 510(k) 2019), PixCell HemoScreen (20 µL, direct fingerstick 510(k) 2023), HemoCue WBC DIFF (10 µL, 5-part differential by imaging), HORIBA Microsemi (CBC from 10 µL), Athelas (white count and neutrophils by computer vision), Abbott Afinion (HbA1c by boronate affinity from 1.5 µL).

Heme Card: four channels from one 20 µL inlet, imaged from below.

Plain-text version

  HEME CARD  (75 x 25 x 3 mm, injection-molded cyclic olefin copolymer, top view; schematic)

   fill window
   [ INLET 20 µL ]==+==> A  dried sphering diluent, 1:200 ======> [ RBC / PLT chamber, 20 µm deep ]
     capillary      |
     metering       +==> B  dried RBC lysis + acridine orange, 1:10 ==> [ WBC chamber, 100 µm deep ]
                    |
                    +==> C  dried sodium lauryl sulfate =========> [ Hb well, 0.13 mm path ] 540 / 880 nm
                    |
                    +==> D  hemolysate + boronate conjugate =====> [ HbA1c membrane ] two-color reflectance
                                                                     (Afinion principle)       [ vent ]

  side view:   LED illumination: white, 470 nm, 540 nm, 880 nm
                  |        |        |
               ===========================  PMMA lid
               ---------------------------  chamber layer (20 µm and 100 µm spacers)
               ===========================  0.17 mm optical floor
                  ^  20x / 0.45 objective, voice-coil focus, XY stage
                  ^  Sony IMX585 camera, 500 nm long-pass + dual-band emission filter

Optics. A 20x/0.45 infinity-corrected objective and a Sony IMX585 sensor (3840 x 2160, 2.9 µm pixels) give 0.145 µm per pixel and a field of 0.557 x 0.313 mm (0.174 mm²) per image. An XY stage steps through fields; a voice coil keeps focus. White light gives brightfield; a 470 nm LED excites acridine orange, which stains DNA green and RNA and granules red.

Counting statistics. Counting error is set by how many cells you count (Poisson: CV = 1 / sqrt(N)). The chamber design is sized so that a normal sample produces enough cells inside the CLIA limits:

Chamber	Dilution	Depth	Cells per mm² at a normal value	Fields (13.9 mm²)	Cells counted	Counting CV	CLIA 2025 limit
RBC	1:200	20 µm	500 (RBC 5.0 million/µL)	80	about 6,960	1.2%	±4%
Platelets	same chamber	20 µm	25 (PLT 250,000/µL)	80	about 350	5.4%	±25%
WBC	1:10, RBCs lysed	100 µm	70 (WBC 7,000/µL)	80	about 970	3.2%	±10%

Scanning is adaptive: when platelets fall below 100,000/µL or white cells below 3,000/µL, the Station scans up to 200 fields so the count stays precise at the low values that matter clinically.

Settling. Cells must lie on the chamber floor to be in focus. From Stokes' law: sphered red cells settle 20 µm in about 15 seconds; white cells settle 100 µm in about 30 seconds; platelets settle 20 µm in about 2 to 3 minutes. The Station images red and white cells at 45 seconds and platelets at about 3 minutes, with a three-plane focus stack near the floor.

Output	Method	Precedent	CLIA 2025 limit
RBC, PLT, MCV, RDW	Brightfield imaging of sphered cells; size from diameter	OLO, HemoScreen	RBC ±4%, PLT ±25%
WBC and 5-part differential	Two-color acridine orange fluorescence plus brightfield; convolutional classifier	OLO, HemoCue WBC DIFF, Athelas	WBC ±10%; differential ±3 SD
Hemoglobin	Sodium lauryl sulfate hemoglobin absorbance at 540 nm, 880 nm reference	Sysmex SLS method; HemoCue microcuvette path	±4%
Hematocrit, MCH, MCHC	Calculated	Standard	Hct ±4%
HbA1c	Boronate affinity on a membrane, two-color reflectance ratio	Afinion	±8%
Flags	Blasts, atypical lymphocytes, nucleated red cells, immature granulocytes, platelet clumps, agglutination	Every hematology analyzer	Images sent to the hub for smear review

The 19 reported parameters: WBC, RBC, hemoglobin, hematocrit, MCV, MCH, MCHC, RDW, platelets, and neutrophils, lymphocytes, monocytes, eosinophils and basophils as both counts and percentages.

6. Engine 2: Chem Disc (centrifugal photometry)

Precedents: Abaxis Piccolo (100 µL, up to 14 analytes per disc, 12 minutes, 11 waived discs), Roche cobas b 101, biosurfit spinit, Samsung LABGEO PT10.

Chem Disc: plasma is separated, metered, diluted and shared among 27 cuvettes read by a ten-wavelength photometer.

Plain-text version

  CHEM DISC  (80 mm diameter, three welded layers; radial layout, center at left, rim at right)

  center ........................................................................................ rim
  (spindle)
     [ diluent blister 400 µL ] --pin--+
                                        v
     [ sample port ] --> [ sample chamber 120 µL ] --> [ separation arm ] --> [ RBC trap ]
                                                             | plasma (4,500 rpm for 75 s, about 680 g)
                                                             v
                                         [ siphon valve ] --> [ meter 20 µL ] --> [ mix chamber, 1:20 ]
                                                                                         |
                                                                                         v
                         [ distribution ring: 24 reagent cuvettes  +  2 reference  +  1 interference index ]
                                                                                         |
                    xenon flash above (fiber-coupled)  ---  every cuvette crosses the beam once per turn
                    10 filtered photodiodes below: 340, 405, 450, 480, 500, 550, 570, 600, 660, 850 nm

Step	Time (s)	Speed	What happens
Load and pierce	0 to 10	0	A pin opens the diluent blister; disc warms to 37 °C
Prime	10 to 20	1,000 rpm	Diluent moves to its holding chamber
Separate	20 to 95	4,500 rpm	Cells pack into the trap (about 680 g at 30 mm radius)
Meter	95 to 110	600 rpm	Siphon primes; 20 µL of plasma is metered
Mix	110 to 140	±15° oscillation	Plasma and 380 µL of diluent mix
Distribute	140 to 160	3,000 rpm	About 13 µL fills each cuvette
React and read	160 to 720	1,500 rpm	Reagent beads dissolve; endpoint and kinetic reads every turn
Report	720	0	Results, interference indices, QC

Photometer. The baseline copies the proven architecture: a xenon flash lamp fired in sync with the rotor's optical index, a reference photodiode to normalize each flash, and ten interference-filtered photodiodes, each with a transimpedance amplifier and gated integrator feeding a 24-bit ADC. Averaging 100 flashes per reading targets absorbance noise below 0.0005. A cost-down path replaces the filter bank with a compact grating spectrometer for 400 to 850 nm plus a dedicated UV channel at 340 nm, where most enzyme assays read.

Metabolic + Lipid disc (17 measured analytes):

Analyte	Method	Read	CLIA 2025 limit
Sodium	Enzymatic, sodium-activated beta-galactosidase	405 nm kinetic	±4 mmol/L
Potassium	Enzymatic, potassium-activated pyruvate kinase with LDH	340 nm kinetic	±0.3 mmol/L
Chloride	Enzymatic, chloride-activated alpha-amylase	405 nm kinetic	±5%
Total CO2	PEP carboxylase with malate dehydrogenase	340 nm endpoint	±20%
Glucose	Hexokinase / G6PDH	340 nm endpoint	±6 mg/dL or 8%
Urea nitrogen (BUN)	Urease / GLDH	340 nm kinetic	±2 mg/dL or 9%
Creatinine	Enzymatic (creatininase, creatinase, sarcosine oxidase, peroxidase)	550 nm endpoint	±0.2 mg/dL or 10%
Calcium	Arsenazo III	660 nm endpoint	±1.0 mg/dL
Total protein	Biuret	550 nm endpoint	±8%
Albumin	Bromocresol purple	600 nm endpoint	±8%
ALT	IFCC method, 37 °C	340 nm kinetic	±15% or 6 U/L
AST	IFCC method, 37 °C	340 nm kinetic	±15% or 6 U/L
Alkaline phosphatase	IFCC, p-nitrophenyl phosphate	405 nm kinetic	±20%
Total bilirubin	Bilirubin oxidase	450 nm endpoint	±20% or 0.4 mg/dL
Total cholesterol	Cholesterol esterase / oxidase / peroxidase	500 nm endpoint	±10%
HDL cholesterol	Direct homogeneous	600 nm endpoint	±20% or 6 mg/dL
Triglycerides	GPO-PAP	500 nm endpoint	±15%
Calculated	LDL (Sampson-NIH equation), non-HDL, eGFR (CKD-EPI 2021), anion gap, globulin, albumin/globulin ratio

Extended disc (8 measured analytes):

Analyte	Method	Read	CLIA 2025 limit
GGT	IFCC substrate	405 nm kinetic	±5 U/L or 15%
Magnesium	Xylidyl blue	550 nm endpoint	±15%
Phosphorus	Phosphomolybdate	340 nm endpoint	±0.3 mg/dL or 10%
Uric acid	Uricase / peroxidase	550 nm endpoint	±10%
Creatine kinase	IFCC, NAC-activated	340 nm kinetic	±20%
Amylase	CNP-G3 substrate	405 nm kinetic	±20%
Iron	Ferene	600 nm endpoint	±15%
Direct bilirubin	Bilirubin oxidase, acid pH	450 nm endpoint	not graded

Interference indices. One cuvette holds diluted plasma with no reagent. Absorbance at 570 and 600 nm gives a hemolysis index, 450 and 480 nm an icterus index, and 660 and 850 nm a lipemia index. Each analyte has its own suppression threshold, set from CLSI EP07 interference studies. The Piccolo already reports these indices; the difference here is that the same indices also govern the other engines' results from the same draw.

7. Engine 3: Immuno Pack (time-resolved fluorescence immunoassay)

Precedents: Boditech ichroma (about 60,000 readers), Wondfo Finecare, Getein 1100, ProciseDx (FDA-cleared time-resolved FRET, 2 to 5 minutes from fingerstick blood), Aidian QuikRead (CRP in 2 minutes).

Immuno strip and time-gated reader: europium keeps glowing after the short background fluorescence has died, so the reader waits, then measures.

Plain-text version

  IMMUNO STRIP (one of up to 6 in a pack), side view

   [ sample port ]  15 µL heparin whole blood
         v
   [ plasma separation membrane ] -> [ europium nanoparticle conjugate ] -> [ nitrocellulose  T line | C line ] -> [ wick ]
         ^
   chase buffer blister (75 µL), released by a plunger 10 s after the sample

  READER HEAD (moves across the strips on a lead screw, 0.1 mm steps)

     365 nm LED pulse (20 µs) --> strip --> 615 nm band-pass filter --> SiPM --> gated integrator
     time gate: wait 50 µs after the pulse, then integrate for 400 µs
     europium emission lasts about 0.5 to 1 ms; plastic and plasma autofluorescence is gone in nanoseconds

Each strip reports one analyte against a lot-specific four-parameter logistic curve carried on the pack's NFC tag, normalized by the control line. Because the strip runs on whole blood, results are corrected for hematocrit using the Heme Card hematocrit from the same visit (QuikRead and the Afinion do similar corrections).

Analyte	Format	Pack	CLIA 2025 limit	Honest note
TSH	Sandwich	Pharmacy	±20% or 0.2 mIU/L	Lateral flow reaches second-generation sensitivity; monitoring of suppressed TSH goes to the hub
Free T4	Competitive	Pharmacy	±15% or 0.3 ng/dL
hs-CRP	Sandwich	Pharmacy	±30% or 1 mg/L
Ferritin	Sandwich	Pharmacy	±20%
25-OH vitamin D	Competitive	Pharmacy	not graded	Target: CDC Vitamin D Standardization-Certification Program criteria
PSA, total	Sandwich	Pharmacy	±20% or 0.2 ng/mL	Abnormal results confirmed at the hub; decisions belong to a clinician
hCG, quantitative	Sandwich	Pharmacy	±18% or 3 mIU/mL
Troponin I	Sandwich	Urgent care	±30% or 0.9 ng/mL	Contemporary, not high-sensitivity; an aid only; chest pain still means the emergency department
NT-proBNP	Sandwich	Urgent care	not in the CLIA table	Validated against a cleared predicate
D-dimer	Sandwich	Urgent care	not in the CLIA table	Exclusion use only with a validated cutoff
Procalcitonin	Sandwich	Urgent care	not in the CLIA table
CRP, wide range	Sandwich	Urgent care	±30% or 1 mg/L

Version 2 high-sensitivity module. High-sensitivity troponin and third-generation TSH need more signal than lateral flow gives. Two precedents show the way: magnetic nanoparticle immunoassays read by frustrated total internal reflection (Philips Minicare, now Siemens Atellica VTLi, 8 minutes) and spinning-chip immunoassays (SpinChip, 10 minutes). Both are patented, so this module needs a freedom-to-operate review or a license.

8. Engine 4: EC Card (urgent-care option)

Precedents: Abbott i-STAT CHEM8+ (CLIA-waived on venous blood), Siemens epoc, Nova StatSensor, Kalium Health.

A single-use card carries thin-film electrodes: ion-selective electrodes for sodium (calixarene ionophore), potassium (valinomycin), chloride and ionized calcium, a silver/silver chloride reference, enzyme electrodes for glucose (glucose oxidase), lactate (lactate oxidase) and creatinine (creatininase chain) read amperometrically at Prussian blue, a urease ammonium electrode for BUN, and a conductivity cell for hematocrit. Like the i-STAT, each card carries a calibrant pouch that wets the sensors before the sample arrives, which is what makes single-use electrochemistry precise. 65 µL, about 2 minutes. It adds ionized calcium and lactate to the menu and gives whole-blood electrolytes fast for urgent care.

Honest limit: a whole-blood potassium electrode cannot see hemolysis. The Station reports EC Card potassium only when the same draw's Chem Disc hemolysis index is below threshold, or when the operator records a free-flowing venous sample.

9. Pre-analytical quality, built in

Check	How	Action
Fill volume	Camera or optical sensor sees the meniscus at each inlet; the disc checks plasma volume	Consumable rejected before it runs
Sample age	Draw kit barcode timestamps collection	Glucose flagged after 30 minutes unspun; whole-blood consumables rejected after 60 minutes (targets, to be validated)
Clots and clumps	Imaging finds fibrin strands and platelet clumps; the disc sees plasma shortfall	Platelets suppressed, CBC flagged, recollect
Hemolysis	Disc index at 570 and 600 nm	Per-analyte suppression (potassium, AST, LDH and others)
Lipemia	Disc index at 660 and 850 nm	Per-analyte suppression
Icterus	Disc index at 450 and 480 nm	Per-analyte flag
Hematocrit extremes	Heme Card hematocrit; disc plasma yield	Immunoassay results corrected; flag below 25% or above 60%
Consumable integrity	NFC lot, expiry and temperature log; on-board control wells	Rejected
Operator	Badge login checked against training records	Untrained users locked out

Example reporting rule, as the patient sees it: "Potassium not reported: the sample shows hemolysis, which falsely raises potassium. A venous draw is recommended." No number is printed. Theranos diluted and reported; the Station suppresses and explains.

10. Electronics

Electronics: a compute module for imaging and software, a real-time controller for motors, optics and heat.

Plain-text version

                    +------------------------------ MAIN COMPUTE -------------------------------+
                    |  Raspberry Pi Compute Module 5 (8 GB) + Hailo-8L NPU on PCIe                |
                    |  Linux: UI, image pipeline, result engine, encryption, sync, audit log      |
                    +-------+----------------+----------------+----------------+------------------+
                            | MIPI CSI-2     | SPI + UART     | PCIe / NVMe    | Ethernet, Wi-Fi, LTE
                            v                v                v                v
                    [ IMX585 camera ]  [ STM32H743 real-time controller ]  [ 256 GB log ]  [ network ]
                                        |  FreeRTOS, watchdog, interlocks
        +-------------------+-----------+------------+-------------------+-------------------+
        v                   v                        v                   v                   v
  [ SPINDLE ]         [ PHOTOMETER ]          [ THERMAL ]          [ IMMUNO SCANNER ]   [ HEME STAGE ]
  BLDC + FOC driver   xenon flash, fiber,     heater pads, TEC,    365 nm LED pulses,   XY steppers,
  optical index       10 filtered PDs, TIAs,  10k NTCs,            615 nm filter,       voice-coil focus,
  0-5,000 rpm         gated integrators,      37.0 ± 0.1 °C        SiPM, gated          4 LED channels
                      24-bit ADC              PID loops            integrator
        +-------------------+------------------------+
        v                   v                        v
  [ EC FRONT END ]    [ OPERATOR I/O ]         [ POWER ]
  AD5941 amperometry  10" touchscreen,         24 V in; 12 V, 5 V, 3.3 V rails;
  and conductivity;   2D barcode, NFC lot      supercapacitor for a safe stop;
  LMP7721 + ADS1262   reader, status light     lid lock solenoid
  for the ISEs

Block	Example parts	Target cost at 1,000 units/yr
Compute	Raspberry Pi CM5 8 GB, Hailo-8L, carrier board	$180
Real-time control	STM32H743, motor and heater drivers, interlocks	$70
Spindle	BLDC motor, field-oriented-control driver, optical index	$90
Photometer	Xenon flash module, fiber, 10 filters, photodiodes, amplifiers, 24-bit ADC	$320
Heme imaging	IMX585 module, 20x/0.45 objective, tube lens, filters, LEDs, XY stage, voice coil	$380
Immuno reader	365 nm LED, 615 nm filter, SiPM, gated integrator, lead-screw carriage	$110
EC front end	AD5941, LMP7721, ADS1262, card connector	$60
Thermal	Heater pads, TEC, thermistors, fans	$60
Operator I/O	10-inch touchscreen, 2D barcode engine, NFC reader, status light	$140
Power and wiring	24 V supply, DC-DC converters, supercapacitor, harnesses	$70
Enclosure and mechanics	Sheet-metal frame, molded covers, drawers, lid lock, isolation mounts	$320
Assembly, test, calibration	Labor and fixtures	$250
Total		about $2,050

Pilot builds of 10 to 60 units will cost two to three times this.

11. Software and the cloud

Station OS. Embedded Linux on the Compute Module with secure boot, signed updates, encrypted local storage, and an offline mode that syncs later.
Real-time firmware. FreeRTOS on the STM32H743: motor control, flash timing, photodiode sampling, heater loops, the immunoassay scanner, the EC front end, interlocks and a hardware watchdog.
Pipelines. Chemistry: blank-corrected absorbance, rate or endpoint, lot calibration, interference rules, reportable-range checks. Hematology: focus stack, segmentation, classification, counts with confidence intervals, flags. Immunoassay: line profile, baseline fit, peak areas, test-to-control ratio, four-parameter curve. EC: sensor slopes from the calibrant, Nernstian conversion.
Result rules. Delta checks against the patient's previous results, critical values that trigger a documented call to the patient's clinician, and the suppression rules above.
Machine-learning governance. Models are locked in the field. Future model updates follow a predetermined change control plan agreed with FDA in advance.
Cloud. Fleet QC, lab director review, results routing with LOINC codes over HL7 v2 and FHIR R4, billing support (CPT codes with the QW modifier when waived), HIPAA, SOC 2, and the premarket cybersecurity requirements for connected devices, including a software bill of materials.

Quality loop: results that fail the rules are suppressed; a drifting analyte locks at that site until the lab director signs off.

Plain-text version

  [ Station run ] --> [ result engine ] --> range, interference, delta and critical-value rules --> [ pharmacist screen ]
         |                   |                                                                          |
         |                   +--> not reportable? --> "not reported" + venous or hub option ------------+
         v
  [ QC record ]  daily electronic QC | liquid QC per lot and every 30 days | on-board control wells
         |
         v  (encrypted, signed)
  [ THIMBLE CLOUD ] -------------------------------------------------------------------------------+
  |  Levey-Jennings per lot and site  |  Westgard multirule  |  patient moving averages (PBRTQC)     |
  |  lab director review queue        |  critical-value call log  |  audit trail: who, what, when     |
  +-------------------------------------------------------------------------------------------------+
         |                                   |
         v                                   v
  drift or QC failure --> that analyte locks at that site      results --> HL7 v2 / FHIR R4 --> EHR, patient app
         |
         v
  service ticket + lab director sign-off before unlock

Patient-based real-time QC (moving averages of, for example, sodium or MCV across all patients at one site) catches slow drift that liquid QC misses. Across a fleet, the cloud can compare every site to every other site running the same lot. This is the honest version of Theranos's remote-control software: it locks results out when quality fails instead of hiding failures.

12. Mechanical layout and scheduling

  THIMBLE STATION, front view (target 42 W x 38 D x 32 H cm, under 15 kg)

  +-------------------------------------------------------------------------------+
  |  [ 10" touchscreen ]                                          ( status light ) |
  |                                                                               |
  |  +---------------+   +-----------------------------+   +--------------------+ |
  |  | BAY 1         |   | BAY 2                       |   | BAY 3              | |
  |  | Heme Card     |   | Chem Disc  (lid-locked)     |   | Immuno Pack        | |
  |  | imaging       |   | 37 °C rotor                 |   | up to 6 strips     | |
  |  +---------------+   +-----------------------------+   +--------------------+ |
  |                                                                               |
  |  [ BAY 4: EC Card, urgent-care option ]    [ NFC + barcode pad ]    [ USB ]   |
  +-------------------------------------------------------------------------------+
     imaging bay on elastomer isolation mounts; rotor on its own sub-frame

Chassis layout (target dimensions).

The scheduler runs the disc's high-speed separation spin during the Heme Card's 45-second settling period, so imaging never happens while the rotor is at 4,500 rpm. Imaging during the 1,500 rpm read phase is allowed because the bay is isolated and exposures are about 1 ms.

  minute      0    1    2    3    4    5    6    7    8    9    10   11   12   13   14   15
  collect     (3 to 5 minutes before loading, outside the Station)
  load        #
  Heme        #########################                                                       CBC + HbA1c, ~5 min
  Disc        ############################################################                    17 analytes, ~12 min
  Immuno      ###########################################################################     up to 6 strips, 10-15 min
  review                                                                                ##    pharmacist review

Run timing for a typical panel.

One rotor means 3 to 4 patients per hour. A busy urgent care needs two Stations or the version-2 dual-rotor chassis.

13. Consumables

Consumable	Storage target	Shelf-life target	COGS target at volume	Price to site (business plan)
Draw kit (lancet or arm collector, EDTA and heparin microtubes, wipes)	Room temperature	24 months	$1.50 (fingertip)	$3
Heme Card	Room temperature, foil pouch with desiccant	12 months	$3.50	$9
Chem Disc	2 to 8 °C, following the Piccolo precedent, until a room-stable bead formulation is validated	12 months	$5.00	$14 (Metabolic + Lipid), $12 (Extended)
Immuno strip	Room temperature	18 months	$1.50	$6
EC Card	Refrigerated with a room-temperature window, following the i-STAT precedent	6 months	$4.00	$10

14. Verification and validation plan

Question	Standard or method
Precision	CLSI EP05 (20 days, 2 runs, 2 replicates)
Linearity and reportable range	CLSI EP06
Interference (hemolysis, lipemia, icterus, common drugs)	CLSI EP07
Method comparison	CLSI EP09, at least 120 samples per analyte against a cleared laboratory analyzer, venous first
Detection limits	CLSI EP17
Reference intervals	CLSI EP28 verification, separately for capillary samples
Capillary versus venous	Paired study under IRB, at least 2,000 participants across ages, hematocrit ranges and skin types
CLIA waiver	Untrained operators at three or more intended-use sites; flex studies under FDA's waiver guidance
Usability	IEC 62366-1 summative study
Electrical safety and EMC	IEC 61010-1 and -2-101 (IVD equipment), IEC 61010-2-020 (centrifuges), IEC 61326-2-6
Software	IEC 62304; cybersecurity under FD&C Act section 524B
Risk	ISO 14971

Acceptance: total error inside the CLIA 2025 limit for each analyte, with a sigma metric, (allowable error minus absolute bias) divided by CV, of 3 or more. Below that the analyte is not offered from capillary blood.

15. Honest limits

Capillary potassium is biased upward by hemolysis. The Station suppresses it when the hemolysis index is high and never "corrects" it.
Capillary total CO2 runs low when tubes are underfilled or exposed to air. It may end up venous-only.
Capillary platelets run lower than venous. Capillary CBCs get their own reference intervals.
No coagulation in version 1. PT/INR needs citrate at an exact ratio. A fingerstick INR strip is a proven add-on later (Roche CoaguChek is the precedent).
No blood gases. They need anaerobic handling.
Lateral flow is less precise than central-lab chemiluminescence. Third-generation TSH, high-sensitivity troponin, sex hormones, B12, folate, PTH, cortisol and serology go to the hub.
Throughput is about four patients an hour per Station.
Version-1 labeling excludes neonates, critically ill patients, patients on chemotherapy and patients with known blood disorders, as the Sysmex XW-100 label does.
Image classifiers can miss rare abnormal cells. Every flag sends images to the hub for human review.
Everything here is a target until verified. The business plan's stage gates say what is dropped if a target is missed.

16. What is borrowed and what is new

Borrowed: every engine. Centrifugal photometry (Abaxis, 1995), imaging hematology (Sight, PixCell, HemoCue), time-resolved fluorescence immunoassay (Boditech, ProciseDx), single-use electrochemistry (i-STAT, 1992), cleared capillary collection (BD, Tasso, YourBio).

New, and worth filing on where the prior art allows:

Four engines in one scheduled chassis, so a single visit returns a CBC, a metabolic and lipid panel and several immunoassays in about 15 minutes.
A Draw kit that splits the sample into dual-additive microtubes and timestamps it, linked to the Station by barcode.
Interference indices measured once and applied across engines: the disc's hemolysis index governs potassium on the EC card and results on the strips from the same draw.
CBC plus HbA1c on one imaging card from one EDTA application.
Fleet-wide patient-based QC across distributed point-of-care sites, with automatic per-analyte lockout and director sign-off.
A patient report that shows the day's QC status and lot for every result.

17. Roads not taken

Optical "scan the drop" (Raman, as Haemanthus proposes). Raman scattering is weak, blood fluoresces and hemoglobin absorbs strongly, and most analytes sit at micromolar to picomolar levels. It may measure glucose one day; it will not quantify 40 analytes soon.
One undifferentiated drop for 200 tests (Theranos). It violates both the anticoagulant rules and the volume budget.
A robot pipettor inside the box (the Edison). It was the Edison's mechanical failure point. Consumables that meter themselves remove it.
Silicon photonics first (Genalyte, SiPhox). Excellent multiplexing, but expensive chips and a slow regulatory path. A candidate for the version-2 immunoassay engine.
Digital microfluidics for everything (Baebies). Flexible and now cleared for PCR, but less proven for routine chemistry at volume. Worth watching.
The continuous patch (the 2003 vision). A different product. Continuous glucose monitors, the Libre Duo glucose-ketone sensor, Biolinq and Nutromics show where it is going; it is not the pharmacy box.