Auckland Bioengineering Institute

Implantable Devices


Small, power-efficient implantable medical devices

The Implantable Devices Group is developing small, power efficient, wireless data acquisition systems that can be implanted for long term monitoring of physiological signals. A driving force has been our need to record sympathetic nerve activity which is small in magnitude, high in frequency content and measurement durations of a month are required.

Our solution to this problem is a compact device capable of recording a wide variety of biopotential signals with bandwidths as high as 8 KHz. We began supplying these devices commercially through a spin-out company Telemetry Research Ltd, and in November 2011, Telemetry Research merged with Millar Instruments to become Millar.

New sensors for blood analysis, blood flow and blood pressure monitoring

Our focus is on power and development of new sensors. Inductive power transfer has been used to provide energy to an ECG telemetry system for a rat. New sensors are being investigated for blood analysis, blood flow and blood pressure.

These devices are low cost, high volume, and have applications in diverse areas starting with the implantable animal monitoring market, moving into clinical monitoring and also adding versatility to other existing devices.

Current projects


Custom-made LED-fibre light module
Custom-made LED-fibre light module

Optogenetics uses light to manipulate neural activity, which has several advantages over conventional electrical stimulation approach including:

  • specific cell-type targeting with precise temporal precision,
  • simultaneous stimulation using different wavelengths of light and
  • it is relatively harmless to targeted tissue.

Optogenetic stimulation offers the prospect of treating lifetime conditions such as Parkinson’s Disease. However, current optogenetics available commercially are mainly connected with wires coming out of the animal's head. This arrangement carries a risk of infection, and is vulnerable to damage from chewing or scratching. Also, current light stimulation systems are generally not suitable for chronic use due to the risk of infection associated with components located outside the brain.

This study aims to investigate the technical feasibility of implementing a fully implantable optogenetics system supporting long-term light stimulation. A custom-made LED-fibre light module has been designed and validated to measure individual cellular response to optical stimulation of photosensitive rat brain slices. This experiment motivates the use of the custom-made LED-fibre optic system for future in vivo chronic rat studies.

Mitigating drift

Custom-made LED-fibre light module

Long term error accumulation of pressure readings (termed drift) significantly affects the operating lifetime of intracranial pressure monitors for hydrocephalus. When drift occurs the real and measured pressures differ, which becomes clinically significant after some time.

Mitigating drift involves studying the contributions from raw pressure dies such as inelastic mechanical deformation and thermal effects of wire bonding. It also involves studying the effect of various encapsulation methods for water vapour transmission and moisture absorption, where encapsulation is required for biocompatibility and sensor protection.

Funding partners

The Implantable Devices Group gratefully acknowledges the support of its funding partners: