This video presents a fully automated desktop workstation for fabricating tissue engineering (TE) scaffolds by assembling microscopic building blocks of dimension 0.5 × 0.5 × 0.2mm3and 60μm thickness. A TE scaffold is a porous supporting structure made of biodegradable material for cells to attach to and proliferate. TE scaffolds fabricated this way enable 3D control of the cells and agents to promote optimal tissue growth. This video outlines the architecture and control strategies of the workstation, and demonstrates its efficiency. Visual and force feedbacks, as well as a haptic exploration, make the assembly robust to large relative errors in the microparts.

This paper presents a novel technique to fabricate scaffold/cell constructs for tissue engineering by robotic assembly of microscopic building blocks (of volume 0.50.50.2 and 60 thickness). In this way, it becomes possible to build scaffolds with freedom in the design of architecture, surface morphology, and chemistry. Biocompatible microparts with complex 3-D shapes were first designed and mass produced using MEMS techniques. Semi-automatic assembly was then realized using a robotic workstation with four degrees of freedom integrating a dedicated microgripper and two optical microscopes. Coarse movement of the gripper is determined by pattern matching in the microscopes images, while the operator controls fine positioning and accurate insertion of the microparts. Successful microassembly was demonstrated using SU-8 and acrylic resin microparts. Taking advantage of parts distortion and adhesion forces, which dominate at micro-level, the parts cleave together after assembly. In contrast to many current scaffold fabrication techniques, no heat, pressure, electrical effect, or toxic chemical reaction is involved, a critical condition for creating scaffolds with biological agents.

This paper presents a monolithic shape memory alloy (SMA) microgripper, which was developed to assemble microscopic building blocks of width 60 /spl mu/m into tissue engineering scaffolds. It consists of two small fingers for grasping, an actuator which changes its shape upon heating by Joule effect and a parallel elastic structure to provide a pullback force on cooling as well as to guide the finger movement. All the elements are laser-cut from the same Ni-Ti-Cu sheet but have different mechanical properties and are used for different functions. Using local laser annealing, a local shape memory effect is introduced on the actuator while leaving other areas in a cold-worked state, i.e. no shape memory effect occurs. The material has nonlinear mechanics and the actuator undergoes large deflections. A numerical method is introduced to compute the nonlinear dynamics of the coupled system formed by the actuator and pullback spring. The predicted deflection and force are in good agreement with the measured ones, and this model can be used to optimize the design.

Describes an integrated approach to design and fabricate scaffold/cell constructs for tissue engineering. With this approach it becomes possible to produce scaffolds with controlled distribution of living cells and growth factors, a critical condition for successful grafting. Our idea consists of building a scaffold/cell construct by robotic micro-assembly of microscopic polymer building blocks. The paper introduces the rationale and concept of this interdisciplinary project and presents some realized steps. A 3D contact FEM simulation has been carried out to study the forces involved on the scaffold elements and micro-gripper during assembly. An error analysis has been performed to evaluate the accumulated error when building a scaffold/cell construct. A dedicated monolithic shape memory alloy micro-gripper has been realized and tested, which is able to handle parts in the range of 50-100 microns.