A multi-degree-of-freedom (DOF) ultrasonic motor consisting of a bar-shaped stator and a spherical rotor was developed. It can generate 3-DOF rotation of the rotor around perpendicular axes using bending vibrations and a longitudinal vibration of the stator, which was designed using finite element analysis. From the simulated driving characteristics, a control method for the ultrasonic motor was proposed. Following this, the driving characteristics of the motor under open-loop control and closed-loop control were measured experimentally. Multi-DOF position control of the rotor was achieved successfully using the proposed control method.

Cell agglomeration is essential both to the success of drug testing and to the development of tissue engineering. Here, a MHz-order acoustic wave is used to generate acoustic streaming in the wells of a 24-well plate to drive particle and cell agglomeration. Acoustic streaming is known to manipulate particles in microfluidic devices, and even provide concentration in sessile droplets, but concentration of particles or cells in individual wells has never been shown, principally due to the drag present along the periphery of the fluid in such a well. The agglomeration time for a range of particle sizes suggests that shear-induced migration plays an important role in the agglomeration process. Particles with a diameter of 45 μm agglomerated into a suspended pellet under exposure to 2.134 MHz acoustic waves at 1.5 W in 30 s. Additionally, BT-474 cells also agglomerated as adherent masses at the center bottom of the wells of tissue-culture treated 24-well plates. By switching to low cell binding 24-well plates, the BT-474 cells formed suspended agglomerations that appeared to be spheroids, fully fifteen times larger than any cell agglomerates without the acoustic streaming. In either case, the viability and proliferation of the cells were maintained despite acoustic irradiation and streaming. Intermittent excitation was effective in avoiding temperature excursions, consuming only 75 mW per well on average, presenting a convenient means to form fully three-dimensional cellular masses potentially useful for tissue, cancer, and drug research.

Cell detachment is essential in culturing adherent cells. Trypsinization is the most popular detachment technique, even though it reduces viability due to the damage to the membrane and extracellular matrix. Avoiding such damage would improve cell culture efficiency. Here we propose an enzyme-free cell detachment method that employs the acoustic pressure, sloshing in serum-free medium from intermittent traveling wave. This method detaches 96.2% of the cells, and increases its transfer yield to 130% of conventional methods for 48 h, compared to the number of cells detached by trypsinization. We show the elimination of trypsinization reduces cell damage, improving the survival of the detached cells. Acoustic pressure applied to the cells and media sloshing from the intermittent traveling wave were identified as the most important factors leading to cell detachment. This proposed method will improve biopharmaceutical production by expediting the amplification of tissue-cultured cells through a more efficient transfer process.

No abstract

A novel control methodologyfor master-slave systems using passive force feedback has been pmposed by the authors. The methodology solves the conventionalpmblems of pwiously developed master-slave systems with force feedback, such as oscillations, compla structures and complicated contml algorithm. In the present papq a multi-fingered exoskeleton haptic device (master hand) with passiveforce feedbockfunction is developed. First, the exoskeleton moster hand with threefingers (I2 degrees of fiedom) is designed and implemented Eachfinger of the master hand consists ofa link mechonism with elastic-shaft joints and clutches. Using link mechanisms, the master hand measures fingertip positions and angla of index fingec middle finger and thumb. Furthermore, if also enables passive force feedback to an operator by the same link mechanism usedfor the geometric measurements. Then. a virtual reality system of human hand is constructed using the master hand and the control methodology. Using the system, sensory evaluations are conducted on human subjects to confirm the usability of the developed master hand and the possibility of the control methodology in the virtual reality system. As a mulr, the subjects possibly recognize the stifiess of the objects in the virtual envimnment.