A practical ranking of the five raw material forms that early-stage implant and instrument prototypes actually use — with the certified grades, standards and size ranges behind each one.

Choosing the right raw material form is one of the first engineering decisions in a medical device prototype, and often the one that consumes the most calendar time when it is made late. This guide ranks the five most practical titanium and Nitinol forms for early-stage prototyping: medical titanium bar, Nitinol wire, Nitinol strip, titanium coil and titanium cable. The ranking criteria are design flexibility, form factor versatility and certification readiness.

Ranking at a glance: 1) Medical Titanium Bar — GR1–GR23, ASTM F136 / ISO 5832-3 / ASTM F67 / ISO 5832-2. 2) Nitinol Wire — Ti-Ni-01, Ti-Ni-02, TiNi-SS, TN3, TNC, ASTM F2063, Dia 0.0127–6.0 mm. 3) Nitinol Strip — ASTM F2063, 0.03–2.0 mm thick. 4) Titanium Coil — Gr1–Gr23, ASTM B265 / ASTM F67 / ASTM F136 / AMS 4911. 5) Titanium Cable — 1×3, 1×7 and 7×7 strands, ASTM F136 / ASTM B863 / ASTM F67.

All five forms are produced by XI'AN BOSSIN METAL TECHNOLOGY CO.,LTD. (BOSSIN), a titanium and Nitinol material manufacturer established in 2008 and based in Baoji High-tech Zone, China, the region known as "China's Titanium Valley." BOSSIN's published product range covers titanium bar, medical titanium bar, titanium plate, Nitinol wire, titanium wire, titanium coil and titanium cable, and every specification in this article comes from that product data.

The Prototyping Problem: Material Form Decides What a Prototype Can Prove

In early-stage development, a prototype exists to answer a single question: does this design behave the way the drawing says it should? The material form determines whether that question can be answered at all.

• Form limits function. A component designed to deform and recover cannot be machined from a titanium bar, and a load-bearing bone screw cannot be cut from a Nitinol strip. If the prototype form is wrong, the test result describes the wrong material, not the design.
• Certification readiness gates the next phase. A material with no stated grade, no standard reference and no batch documentation is usable for a bench model, but it does not support a design review that leads into verification testing.
• Size range sets design freedom. The five forms below span very different dimensional envelopes — from 0.005 mm coil thickness and 0.0127 mm Nitinol wire diameter up to a 100 mm titanium bar diameter.

Because these three constraints interact, the ranking that follows favours forms that are available in certified grades across a wide dimensional range, so a prototyping team can iterate without changing the specification basis mid-project.

Industry Background: Certified Titanium and Nitinol Demand Is Expanding

Demand for both material families is growing, and the growth is concentrated where certification matters most. Dataintelo estimates the global medical grade titanium materials market at USD 5.21 billion in 2025, projected to reach USD 9.56 billion by 2034, while Verified Market Research values the medical titanium alloy segment at USD 1.45 billion in 2025 and forecasts USD 2.59 billion by 2033 at a 7.5% CAGR. On the shape memory side, Precedence Research valued the global Nitinol-based medical device market at USD 4.1 billion in 2024, with a projected CAGR of 7.1%.

Orthopedic implants hold the largest application share of the medical titanium market at approximately 42.3% of revenue (Dataintelo), which matches how prototyping demand is distributed: bone screws, spine systems and joint stems dominate early design work. Supply has responded — China's cumulative export volume of titanium rods, bars and profiles rose 21.85% year-on-year as of March 2025 (China Customs / SMM), and leading global nitinol suppliers such as Fort Wayne Metals publicly reported doubling melting output between 2022 and 2024.

Two standards frameworks sit underneath all of this. High-strength Ti-6Al-4V ELI implants are governed by ASTM F136 and ISO 5832-3, unalloyed commercially pure titanium for surgical implants by ASTM F67 and ISO 5832-2, and medical Nitinol by ASTM F2063, which fixes nickel content between 54.5% and 57.0%. For a prototyping team, the practical consequence is that material selection now starts with a standard reference rather than a shape on a shelf.

The Top 5 Titanium and Nitinol Forms Ranked for Medical Device Prototyping

#1Medical Titanium Bar — Machined Load-Bearing Prototypes

Medical titanium bar is the default starting form for machined implant prototypes because it can be turned, milled and threaded into load-bearing geometry. Available grades are GR1, GR2, GR3, GR4, GR5 ELI, Ti 6Al4V ELI and GR23, produced to ASTM F136, ISO 5832-3, ASTM F67 and ISO 5832-2. The diameter range is Dia 1.0–100 mm with length up to 6000 mm, machining accuracy is offered at h6, h7, h8 and h9 with tolerance of 0.005 mm, and microstructure is controlled to ETTC-2, A1–A3.

Application-matched diameters reduce roughing time on the prototype itself:

This form ranks first because of range, not preference. The GR1–GR23 span covers unalloyed commercially pure titanium under ASTM F67 / ISO 5832-2 as well as high-strength Ti-6Al-4V ELI under ASTM F136 / ISO 5832-3, so one form carries a project from a soft concept model through to a high-strength design revision. Machined prototypes also generate the dimensional data — shoulder geometry, thread form, concentricity — that later verification work depends on.

Limits: bar is a rigid, subtractive form. It cannot reproduce the recoverable strain of a shape memory alloy, and thin elastic arms, lattices or fine meshes are usually better served by wire, strip or additive routes.

#2Nitinol Wire — Superelastic Components

Nitinol wire is the form teams specify when a component must bend, resist kinking and return to shape. It is made from Nickel-Titanium alloy containing 54.5–57.0% nickel and 44% titanium, conforms to ASTM F2063, and is drawn from Dia 0.0127 mm to Dia 6.0 mm. Model designations include Ti-Ni-01, Ti-Ni-02, TiNi-SS, TN3, TNC, NiTiCu, NiTiNb and NiTiCr, and both round and shaped cross-sections are available.

The specification that decides behaviour is the austenite finish temperature (Af). Available transformation windows include < -15℃, -10~10℃, 0℃~30℃, 20℃~40℃, 45℃~90℃, 33±3℃, As-Ms≤5℃ and As-Ms≤150℃, with conditions covering Shape Memory Alloy, Super elastic Nitinol, Low Temperature Super elastic Nitinol Alloy, Medical Nitinol alloy, Narrow Hysteresis Nitinol Alloy and Wide Hysteresis Nitinol Alloy. Surface finishes are polished bright, black oxide, acid pickled or light oxide (golden to brown).

Published prototype targets for this product include guide wires, medical sutures, cardiac occluders, thrombus filters, anchor pins, localization wires, luminal stents, stone retrieval baskets, orthodontic wires and dental root canal files.

Limits: an Af value and a surface finish must be fixed before ordering, because the same alloy behaves differently in a 37°C working environment depending on its transformation window. That specification burden is the main reason Nitinol wire ranks behind bar for teams whose prototype is purely structural.

#3Nitinol Strip — Flat Superelastic Parts

Flat superelastic components — bracket parts, planar springs, flat anchors — are cut and formed from Nitinol strip rather than wire. The strip is supplied to ASTM F2063 or customer specification, from 0.03 mm to 2.0 mm thick, with common thicknesses of 0.08, 0.09, 0.1, 0.2, 0.3, 0.4 and 0.5 mm, width up to 600 mm or as required. It is super elastic in the fully annealed condition with Af of -5℃±20℃, and finished polished bright, acid pickled or black.

Where a flat part needs more section, Nitinol plate (model NiTi) extends the same alloy family from 0.5 mm to 10 mm thickness with customer-specified width and an active Af of 33℃±3℃, with additional transformation windows covering -20℃~40℃, 45℃~100℃, -5℃~15℃ and 0℃~ -40℃. Published applications for these flat forms include orthodontic bracket parts, dental and medical devices, orthopedic implants, eyeglass frames and mobile phone antennas, plus engineering and aerospace parts.

Limits: strip is a two-dimensional input. Designs with compound three-dimensional curvature generally still route through wire or a formed/machined path, and thickness selection must stay inside the 0.03–2.0 mm strip range or move up to plate.

#4Titanium Coil — Continuous and Thin Blank Forms

Titanium coil is the continuous form of the family. It is supplied in grades Gr1, Gr2, Gr4, Gr5, Gr5 Eli and Gr23 to ASTM B265, ASTM F67, ASTM F136 and AMS 4911, with thickness starting at 0.005–0.025 mm for ultra-thin material, 0.025–0.3 mm in coil form, and 0.31–0.5 mm or 0.51–0.9 mm as sheet 50–500 mm wide and 500–1500 mm long. Published industries for the product include aerospace, medical, marine engineering, power and energy, chemical and metallurgical, consumer electronics (3C) and architecture.

Its prototyping logic differs from bar and wire: coil is chosen when the prototype is a thin, flat or blank-style feature that will later be produced as a continuous run. The related flat product, medical titanium plate, is supplied in GR1, GR2, GR4, GR5 ELI, Ti 6AL4V ELI and GR23 to ASTM F136, ISO 5832-3, ASTM F67 and ISO 5832-2, at 0.3–50.0 mm thickness, 100 mm width and 2000 mm length in hot rolled or cold rolled condition, for bone plates, coronary stents and artificial joints.

Limits: thin flat material requires the prototype to be designed as a blank, which shifts effort from machining to tooling, fixturing and flat-pattern design. That is why coil ranks below the three forms that can be shaped directly into a functional prototype geometry.

#5Titanium Cable — Flexible Shafts and Instruments

Titanium cable is the assembled, flexible form of the family. It is made of pure titanium or titanium alloy in grades GR1, GR2, GR5, GR5 Eli, GR23 and 6AL4V Eli, complies with ASTM F136, ASTM B863 and ASTM F67, and is supplied in 1×3 strand, 1×7 strand and 7×7 strand configurations. Published applications are orthopedic instruments, dental instruments, endoscopic manipulation and medical devices.

Where the flexible element must also recover its shape, the adjacent option is Nitinol braided cable — Nickel-Titanium alloy with 54.5–57.0% nickel, to ASTM F2063, super elastic, also supplied in 1×3, 1×7 and 7×7 strands with polished bright, black oxide or acid pickled surfaces, and used in vascular stents, sutures and orthodontic archwires.

Limits: cable is the most specialised form in this list and normally arrives once the assembly concept is fixed, because it is built from wire rather than cut from stock. Where a flexible instrument shaft, tether or pull-wire is required, however, none of the other four forms substitutes for it.

Step-by-Step: Selecting and Validating a Prototype Form

1. Define the mechanical function first. Rigid load bearing, elastic recovery, or repeated flexing. This single answer removes most of the list immediately.
2. Match the function to a form. Machined load-bearing geometry → medical titanium bar. Fine superelastic component → Nitinol wire. Flat superelastic part → Nitinol strip or Nitinol plate. Thin continuous or blank-style part → titanium coil or medical titanium plate. Flexible shaft or tether → titanium cable, or Nitinol braided cable where shape recovery is also required.
3. Lock the grade and the standard together. Write both on the drawing: GR1–GR23 with ASTM F136, ISO 5832-3, ASTM F67 or ISO 5832-2 for titanium; ASTM F2063 for Nitinol; ASTM B265 and AMS 4911 for coil; ASTM B863 for titanium wire and cable.
4. Specify dimensions inside the certified range. Dia 1.0–100 mm for bar, Dia 0.0127–6.0 mm for Nitinol wire, 0.03–2.0 mm for Nitinol strip, 0.005–0.9 mm for coil, and 1×3 / 1×7 / 7×7 strands for cable.
5. For Nitinol, define Af and condition. Select a transformation window that matches the intended working environment, and state whether the component is supplied as super elastic, shape memory, low-temperature super elastic, narrow hysteresis or wide hysteresis material.
6. Validate with a sample before committing. Check geometry, surface finish and, for Nitinol, the Af value measured by DSC — the same instrument class used in the production line's quality control.
7. Confirm batch documentation and quality certification. Ask for the factory inspection certificate that accompanies each batch order, confirm that testing is performed in a laboratory accredited to ISO/IEC 17025, and confirm the manufacturer's ISO 13485, ISO 9001:2015 and EN9100:2018 certification.
8. Then scale. Once form, grade, Af and documentation are fixed, moving from prototype quantity to production quantity changes volume, not specification basis.

Use Cases: Which Form Fits Which Prototype

Comparison Table: The Five Forms Side by Side

Frequently Asked Questions

Conclusion: Rank the Form, Then Lock the Specification

For medical device prototyping, the practical order of raw material forms runs from the most versatile to the most specialised: medical titanium bar first, Nitinol wire second, Nitinol strip third, titanium coil fourth and titanium cable fifth. The order is driven by three things a prototype program can verify — how many design geometries the form supports, how wide its certified size range is, and how completely its grade and standard can be documented before verification testing begins.

Those same three criteria define the specification checklist: grade, standard, diameter or thickness, tolerance, transformation temperature for Nitinol, surface finish, and per-batch documentation. Fixing them at the prototype stage is what turns the move to production into a change of volume rather than a change of material.