Designing TACTO: Engineering a Robotic Fingertip Inspired by Human Mechanics
- Ana Aranda Loureiro
- Aug 19
- 5 min read
Most people never think about fingertips. At Touchlab, we've spent the last several years thinking about almost nothing else. Not the robotic hand, not the actuator, not the control software—but the final few millimetres where a robot actually meets the world.
That focus led to TACTO, our latest robotic fingertip.
As a company specialising in tactile sensing, we spend every day studying touch: how forces move through compliant materials, how contact changes under load, and how objects begin to slip. Over time, one thing became increasingly clear: before a robot can sense touch well, it first has to make good contact.
This article focuses on the mechanical design of TACTO — while sensing, electronics and AI are integral to the full system, here we isolate the mechanical layer to explain how the fingertip itself was designed to create stable, human-like contact.
The Most Overlooked Part of Robotic Manipulation
Every robotic manipulation task, regardless of how sophisticated its planning or control software may be, ultimately depends on a physical interface: the surface touching an object.
If that contact is unstable, no amount of software can fully compensate.
A robot may know exactly how to grasp an object, but if its fingertip cannot create stable contact, distribute force effectively, or adapt to an object's geometry, the rest of the system is left compensating for a mechanical limitation it was never designed to solve.
This is one of the most overlooked parts of robotics—and one of the most common sources of failure.
Objects slip.
Delicate products become damaged.
Irregular geometries become difficult to handle.
In many cases, these aren't failures of perception or control. They're failures of contact mechanics.
Learning From Biology to Design a Better Robotic Fingertip
When we began designing TACTO, we weren't trying to copy biology.
We were trying to understand why the human fingertip works so well.
Humans manipulate an extraordinary range of objects every day—from fruit and textiles to tools, cables and electronics—without consciously adjusting every movement. Much of that adaptability comes from the mechanics of the fingertip itself.
For us, biology wasn't a blueprint. It was a source of engineering principles.
Understanding those principles required more than mechanical design alone. It brought together expertise across tactile sensing, materials engineering, robotics, AI and product design. Each discipline offered a different perspective on the same physical interaction: mechanics create the contact, tactile sensing measures it, and intelligence decides how to respond.
That multidisciplinary approach shaped every design decision behind TACTO.
Three Design Principles That Kept Proving Themselves
 | Across six generations of prototypes, we explored different geometries, materials and compliance profiles. While many details evolved, three mechanical principles consistently proved themselves. |
1. Contact Grows with Curvature
Many robotic fingertips are relatively flat because flat surfaces are simple to manufacture.
Human fingertips aren't.
Their carefully balanced curvature allows the contact area to grow naturally as force increases. Rather than concentrating force into a single point, the fingertip gradually wraps around the object, creating a larger and more stable contact patch.
The result is better grip with lower peak pressure.
2. Compliance Should Be Layered
A human fingertip isn't uniformly soft.
Its stiffness changes gradually from the surface towards the bone.
That gradient allows the fingertip to conform to small surface features while still transmitting significant gripping forces.
This taught us an important lesson: softness and strength don't have to be competing requirements. With the right mechanical architecture, they reinforce each other.
3. Rigidity Still Matters
Although human fingertips deform, they do so around a rigid internal structure.
The bone provides stability. The surrounding tissue provides adaptability.
Together, they create a contact interface that can accommodate complex geometries without collapsing under load.
These three principles became the mechanical foundation of TACTO.
The exact geometry and material formulations are proprietary, but the engineering logic behind them is universal.
Turning Contact Mechanics into a Functional Robotic Fingertip
Understanding these ideas was only the beginning. The real challenge was translating them into a fingertip that could survive industrial environments, be manufactured consistently, and integrate with existing robotic systems. TACTO combines a rigid internal structure—analogous to the distal phalanx—with a compliant elastomer shell engineered to deform in a controlled way. As load increases, the elastomer progressively conforms around the object rather than simply compressing against it. |  |
That behaviour produces three important mechanical effects simultaneously:
Dynamic Contact Growth: The contact area increases with force. Instead of pushing harder into a single point, the fingertip wraps further around the object's surface.
Distributed Pressure: Pressure spreads across a larger area. Lower peak contact pressure reduces the risk of damaging delicate products while improving overall grasp stability.
Enhanced Slip Resistance: The grip becomes significantly more resistant to slip. A larger contact patch increases effective friction, particularly during shear and torsional loading—the conditions where many robotic grasps fail.
For a tactile sensing company, this behaviour offers another important advantage.
The growing contact patch isn't just good mechanics—it's the signal our tactile sensors are designed to measure. As the elastomer deforms, our sensor captures how pressure spreads, where forces concentrate, and how those patterns evolve before an object begins to slip.
Better mechanics create better tactile information.
Designed for Real Applications
Performance is only part of the challenge. Industrial components also need to be maintainable, adaptable and reliable over millions of operating cycles.
Rather than treating the elastomer as a permanent component, we designed it to be replaceable.
When the contact surface eventually wears—as every elastomer will—only the outer skin needs to be exchanged, reducing maintenance time and extending the service life of the fingertip.
The modular design also allows compliance to be selected for different applications.
Interchangeable skins are available from Shore A10 to A40.
[Figure 1-3: Comparison of A10 and A40 elastomers under identical loading conditions.]
Softer materials (A10-A20) maximise conformity and minimise contact pressure, making them well suited to delicate products such as food, textiles and fragile components.
Harder materials (A30-A40) provide greater positional stability, repeatability and durability for higher-force industrial processes.
Instead of treating compliance as a fixed material property, we designed it as an engineering parameter that can be selected to match the application.
Integrating the TACTO Robotic Fingertip with Existing Systems
Our fingertip was never intended to be tied to a single robotic platform.
TACTO has already been successfully adapted to different hands and grippers including the Allegro Hand, Shadow Hand, Tesollo systems, and Robotiq, as well as custom manipulators.
Improving manipulation shouldn't require replacing an entire robotic system.
Designed to Scale
Many compliant robotic components demonstrate impressive results in research laboratories but rely on manufacturing processes that are difficult to scale.
From the beginning, we wanted TACTO to be different.
Manufacturability was treated as a design requirement from the earliest stages of development. Geometry, material selection and tolerances were developed alongside Design for Manufacturing principles, with injection moulding chosen as the production process from the outset.
Consistent manufacturing produces consistent mechanics.
When the behaviour of a compliant fingertip depends on subtle relationships between geometry, stiffness and deformation, repeatability is just as important as performance.
The Takeaway
TACTO is the result of years spent studying one of the smallest—but most important—interfaces in robotics.
Its design is built around a handful of engineering principles: contact that grows instead of concentrates, application-specific elastomers with different compliance levels, a rigid structure wrapped in a compliant interface, and a modular architecture designed to create stable, human-like contact that enhances tactile sensing performance in real industrial use.
None of these ideas is revolutionary on its own.
What matters is applying them together, deliberately and without compromise.
Because no matter how intelligent a robot becomes, every interaction with the physical world still begins with contact. And good contact is where good touch begins.
Building or optimising a robotic manipulation pipeline? Whether you operate on Allegro, Shadow Hand, Robotiq, or a custom manipulator, our team can help you integrate TACTO into your existing system.
