> For the complete documentation index, see [llms.txt](https://delta-robotics.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://delta-robotics.gitbook.io/docs/hardware/thermoflex/tf-mk1-muscle.md).

# TF Mk.1 Muscle

The TF Mk.1 Muscle, a dual-coil Nitinol actuator that lifts up to 25 pounds in about 2 seconds on a 25 V supply, with full electrical and mechanical specs

*Pronunciation: Ther-moh-fleks mark one muscle*

The TF Mk.1 Muscle is a dual-coil Nitinol actuator. It contracts when heated by current and returns as it cools, delivering muscle-like linear pull for robotics and motion projects. Drive it with the TF Node Controller and the ThermoFlex Python API.

<figure><img src="https://1078621213-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fm2yg571oTEEeXffjpREo%2Fuploads%2Fgit-blob-f0227712c0cc23c26f828f19b34a2c2f86d2b110%2F2025-02-15%2015.12_edited.png?alt=media" alt="" width="375"><figcaption><p>The TF Mk.1 Muscle.</p></figcaption></figure>

## Specifications

### Electrical

| Parameter             | Minimum              | Maximum                |
| --------------------- | -------------------- | ---------------------- |
| Nominal voltage       | 3 V                  | 25 V                   |
| Resistance            | 235 mOhms (Af)       | 250 mOhms (Mf)         |
| Instantaneous current | (Dependent on PWM %) | 106 A (2s contraction) |

### Mechanical

| Parameter  | Minimum                        | Maximum |
| ---------- | ------------------------------ | ------- |
| Pull force | 5 lbs (extension return force) | 25 lbs  |

### Timing

| Parameter        | Minimum | Maximum   |
| ---------------- | ------- | --------- |
| Contraction time | -       | 2s @ 25 V |

Question about specific values? Ask Kevin: <kevin@deltaroboticsinc.com>

## Contraction test results

A single full actuation, measured on the bench with a current-limited supply.

| Test parameter          | Value                                                     |
| ----------------------- | --------------------------------------------------------- |
| Power supply            | Variable supply set to 15 A, monitored on an oscilloscope |
| Load                    | None                                                      |
| Set current             | 15 A                                                      |
| Time to contract (TTC)  | 35.311 s                                                  |
| Total power consumption | 1923 J (about 0.5 Wh)                                     |

<figure><img src="https://1078621213-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fm2yg571oTEEeXffjpREo%2Fuploads%2Fgit-blob-66508a0a7c8ec3c92e5e7a20b2c5cf13607abafe%2Fimage.png?alt=media" alt=""><figcaption><p>What this means: the graph shows the total power consumption for a full actuation over 35 seconds. Standard actuations with the TF Node Controller are under 2 seconds.</p></figcaption></figure>

## Related pages

* [TF Node Controller](/docs/hardware/thermoflex/tf-node-controller.md): The electronics that drive this muscle.
* [ThermoFlex Python API](/docs/software/thermoflex-python-api.md): Command contractions from Python.
* [Wire](/docs/hardware/nitinol/wire.md): The Nitinol behind the muscle.
* [Quickstart: your first flex](/docs/get-started/quickstart.md): Run your first contraction.